1. What will taenia cause? Intestinal obstruction 2. A patient have renal stone, hypercalcemia, increase PTH-- Parathyroid hyperplasia Parathyroid benign Parathyroid metaplastic 3. Chronic cervititis, dyspareunia, whitish vaginal discharge Edema of subepithelial matrix-- Hemorrhage of submucosal lesion Reactive atypia of endocervical epithelium Mononuclear cells infiltrate in squamo-columnar junction 4. 8cm tetranoma, skin, hair, teeth, ovarian cyst Mature cystic tetranoma 5. Diagnosis of leprosy Acid fast stain skin scraping 6. Prednisolone (steroid) for crohn disese, leads to Hypocalcemia 7. Prion disease, due to: Mutation of cellular protein gene 8. Backward design Case control 9. Acute cholecystitis Jaundice 10. A children have leukemia, what vaccine should be prohibited Mumps vaccine 11. Smoker, diabetic, GERD, gastric reflux, redness at lower end of esophagus, diagnosed as esophagitis, due to?---- Gastric acid Tobacco HSV Candida sp. 12. Antiepileptic drugs side effect Nystagmus 13. Casts found in acute pyelonephritis---- RBC cast WBC cast Granular cast Fatty cast 14. Opiod is contradict with undiagnosed abdominal pain, this is because---- Prevent masking of visceral pain Obstruction of blood flow Damage to internal organ Abdominal perforation 15. Alkaline, yellow MacConkey, gram negative, bacilli, positive urease test Proteus sp 16. Diabteic, dyslipidemia, middle cerebral artery infarct Atherosclerosis 17. According to the National Health & Morbidity Survey 2015, NCD accounted for 74% of deaths in Malaysia. Which of the following causes the most deaths in Malaysian hospitals?---- Diseases of circulatory system Diseases of the respiratory system Neoplasms Diseases of digestive system 18. Epithelial neoplastic, post-menopausal bleeding, ulcers, no mass Choriocarcinoma 19. Increase gentamicin, inhibit DNA gyrease, hematuria, renal insufficiency, iatrogenic nephrotoxicity, complication? Thrombotic microangiopathy 20. Oxytocin contraindicated with?---- History in gestational diabetes History in eclampsia History in caeserean section Early rupture of membrane 21. Spironolactone (potassium sparing) acts on Collecting duct-- Loop of Henle Distal convoluted tubule Proximal convoluted tubule 22. Patient has edema, spikes in the basement membrane, proteinuria, which of the following statements is correct? Subepithelial immune deposit complex 23. Antihelminth drug, filiarasis, which drug should be given? Praziquantel 24. Patient has IDC (invasive ductal carcinoma), positive HER2, what drug should be given? Tamoxifen 25. 13 y/o boy has testicular pain after evaluation, he is suspect to have---- Testicular torsion Orchitis Epididymitis Testicular tumor 26. Disease is not an inevitable outcome of the host-pathogen interaction and, furthermore, pathogens can express a wide range of virulence. Which of the following statements best describe virulence for the above scenario?---- Ability to cause clinical disease Ability to evoke an immune response Ability to cause severe disease Ability to cause death Candida albicans 27. Patient undergo examination, found out thick, cheese cottage discharge, she is suspected with the infection of: 28. Patient is diagnosed as tetanus, infected by clostridium tetani, which examination should be carried out? Wound swab 29. Patient has increased pigmentation in the oral mucosa, decreased sodium level with increased potassium level, increase in cortical ACTH, he is diagnosed with adrenal insufficiency, which of the following statements matches? Waterhouse-Friderichsen Selective (SAOR) 30. Anovulatory infertility, she is treated with clomiphene, which of the following best describe the MOA---- Inhibit FSH release Inhibit estrogen receptor synthesis Down regulated GnRH 31. Increased T3, T4, decrease TSH, diagnosed as Graves disease, microscopy appearance: Scalloped 32. HIV, early stage Protein 17 33. A 56 y/o Schizophrenia patient on haloperidol presents with symptoms of tardive dyskinesia. The psychiatrist decides to change her medication to clozapine. Which of the following pharmacological action of cloazapine best explains the change of drug? Has a low affinity of for dopamine D2 receptors-- Has greater antagonist at muscurinic receptors Blocks dopamine release Activates GABA receptos 34. How do HPV warts occur? HPV infects surface layer of epithelium 35. A malnourished 2 y/o (weight 4.75kg) is undergoing the proper nutritional programme who gains 32% more weight in three weeks (weight 6.28kg). Which of the following is the most accurate direct nutritional status assessment?---- Clinical examination Biochemical examination Anthropometry Vital statistics 36. Dysentery diarrhea, pear shaped, what is the causative agent? Giardia lambia (watery)-- Entamoeba histolytica Entamoeba coli Balantidium coli 37. Obstructive uropathy, narrow right ureter, scarring, hydronephrosis, polyuria Decrease in glomerular filtration 38. Jaundice, increased IgM, diagnosed as Hepatitis E, why? Complement activation 39. Peutz Jeghers Polyps, mutation STK 11 Superficial columnar & goblet 40. Diffuse infiltrative malignant neoplasm Adenocarcinoma 41. A patient has rabies, fast spreading to CNS, due to: Migration of infected epidermal dendritic cell 42. Infective stage of fasciola Cercaeria 43. P value 0.4 44. Increase extracellular fluid, increase permeability, affect interstitial space Vasogenic edema 45. Entamoeba histolytica, in order to eradicate cyst, treated with? Metronidazole 46. Maternal mortality rate indicate level of health system development, this is because of: Maternal death irrespective of duration of pregnancy 47. Hematuria, solidarity nodular mass lesion, cluster of pleomorohic malignant cells Clear cell carcinoma 48. Epidermiologists have identified the epidemiologic triad of diseases as a traditional model of infectious disease causation. Which of the following combinations is the component of the epidemiological triad? Agent, host, environment -- Primary prevention, secondary prevention, tertiary prevention Time, place, person Souce, mode of transmission, susceptible host 49. Fixed short breathe, dyscrasias, dysentery treated by sulphanethoxazole Sulphur drug induced anemia 50. Schistosoma haematobium, investigation Urine examination 51. CNS demyelination, leg weakness, oligoclonal band, Autoimmune demyelination Abrupt withdrawal 52. Systemic lupus erythematosus is treated with corticosteroid, leads to rebound hypertension, due to:---- Psycho depend Hyperglycaemia Acute adrenal insufficiency Somatotropin 53. A 3 y/o girl presents to the Pediatric Clinic with short stature and appears to have loose skin on her neck. Cytogenetic testing reveals an XO karyotype - (Turner syndrome). Which of the following drugs is the most likely for her to achieve appropriate heigh for her age?---- Growth hormone-releasing hormone (GHRH) Adrenocorticotropin Corticotropin-releasing hormone (CRH) 54. Campylobacter jejuni virulence factor cause inflammation Adhesins 55. Type 1 diabetes mellitus treated by insulin, avoid the same injection side, why? Lipodystrophy 56. Insomnia, anxiety, increase inhibitory effect of GABA on neuronal excitability, should be treated with? Benzodiazepine: increase chloride influx, increase negative charge, alter voltage, brain resist nerve impulse 57. Hypopituitarism, non-functional pituitary adenoma, which one will be the first affected?---- Breast Ovary Thyroid Cortex 58. A patient has gradual hearing loss, sensorineural hearing loss, cell circumscribed neoplasm at cerebellopontine angle at posterior cervical fosa, microscopic shows Antoni A & B and verocay necrosis, which cells are affected? Schawann cells 59. Meningitis infected by Cryptococcus neoformas, treated with amphotericin B + flucytosine, why combination drugs? Prevent resistance to antifungal 60. Painful genital, diagnosed with chancroid, diagnostic test? Nucleic acid probe: to test chancroid CA (hemophilus ducreyi write full questions for all 60..n explain the ans

Reading File

Given the large scope (60 MCQs), I'll answer all from my medical knowledge directly, providing complete questions and full explanations for each.

60 MCQ - Complete Questions & Explained Answers

Q1. Taenia (tapeworm) infestation most commonly leads to which complication?

A) Liver abscess
B) Intestinal obstruction ✓
C) Renal failure
D) Pneumonia

Answer: Intestinal obstruction Taenia species (T. solium, T. saginata) are large intestinal cestodes. Heavy worm burdens can cause mechanical blockage of the intestinal lumen leading to obstruction. T. solium larvae (cysticercosis) can also cause CNS symptoms, but the classic direct complication of the adult worm is intestinal obstruction.

Q2. A patient presents with renal stones, hypercalcemia, and elevated PTH. What is the most likely diagnosis?

A) Parathyroid hyperplasia/benign adenoma ✓
B) Parathyroid metaplasia
C) Parathyroid carcinoma
D) Vitamin D toxicity

Answer: Parathyroid benign adenoma (Primary Hyperparathyroidism) The triad of hypercalcemia + elevated PTH + nephrolithiasis (renal stones) is classic for primary hyperparathyroidism. The most common cause (~85%) is a benign parathyroid adenoma (solitary). Parathyroid hyperplasia accounts for ~15% and is associated with MEN syndromes. Malignant parathyroid carcinoma is rare (<1%). In primary hyperparathyroidism, PTH is inappropriately elevated for the calcium level, driving osteoclast activity and hypercalcemia, with calcium spilling into urine causing stones.

Q3. A patient with chronic cervicitis presents with dyspareunia and whitish vaginal discharge. Histology shows changes at the squamo-columnar junction. What is the most characteristic microscopic finding?

A) Edema of subepithelial matrix
B) Hemorrhage of submucosal lesion
C) Reactive atypia of endocervical epithelium
D) Mononuclear cell infiltrate at the squamo-columnar junction ✓

Answer: Mononuclear cell infiltrate at the squamo-columnar junction Chronic cervicitis is characterized histologically by a chronic inflammatory infiltrate - predominantly lymphocytes, plasma cells, and macrophages (mononuclear cells) - concentrated at the squamo-columnar junction (transformation zone). The squamo-columnar junction is most susceptible to infection and metaplastic change. Reactive atypia can be seen but is a secondary change. Edema and hemorrhage are features of acute cervicitis.

Q4. An 8 cm ovarian cyst in a woman contains skin, hair, and teeth. What is the diagnosis?

A) Immature teratoma
B) Dysgerminoma
C) Mature cystic teratoma (dermoid cyst) ✓
D) Serous cystadenoma

Answer: Mature cystic teratoma (dermoid cyst) A cystic ovarian mass containing ectodermal derivatives - skin, hair, teeth, sebaceous material - is pathognomonic of a mature cystic teratoma (dermoid cyst). These are the most common ovarian germ cell tumors in women of reproductive age, arising from all three germ layers but predominantly ectodermal. They are benign (unlike immature teratomas). The presence of a Rokitansky protuberance (dermal plug) is characteristic on imaging and gross pathology.

Q5. Which investigation is the gold standard for diagnosing leprosy (Mycobacterium leprae)?

A) Blood culture
B) PCR
C) Acid-fast stain of skin scraping (slit-skin smear) ✓
D) ELISA

Answer: Acid-fast stain of skin scraping (slit-skin smear) M. leprae cannot be cultured in vitro. The standard diagnostic method is the slit-skin smear - skin scrapings from lesions (earlobes, nasal septum, affected skin) stained with Ziehl-Neelsen (acid-fast) stain to demonstrate red acid-fast bacilli. The bacterial index (BI) and morphological index (MI) quantify bacillary load. In paucibacillary (tuberculoid) leprosy, smears may be negative - skin biopsy becomes essential. PCR is increasingly used but slit-skin smear remains the field standard.

Q6. A patient with Crohn's disease is treated with prednisolone (corticosteroid). What metabolic complication is expected?

A) Hypocalcemia ✓
B) Hyperkalemia
C) Hypoglycemia
D) Hyponatremia

Answer: Hypocalcemia (and osteoporosis) Corticosteroids such as prednisolone cause hypocalcemia through multiple mechanisms:

Decrease intestinal calcium absorption (antagonize vitamin D action on gut)
Increase renal calcium excretion
Inhibit osteoblast activity, reduce bone formation
Stimulate PTH secretion (secondary hyperparathyroidism)

The net result is decreased serum calcium, reduced bone density (osteoporosis), and increased fracture risk. This is why calcium and vitamin D supplementation is recommended for patients on long-term steroids.

Q7. Prion disease (e.g., Creutzfeldt-Jakob disease) is caused by:

A) Viral infection
B) Bacterial toxin
C) Mutation of cellular protein gene (PrP gene) ✓
D) Autoimmune destruction

Answer: Mutation of cellular protein gene Prion diseases are caused by misfolded prion proteins (PrPSc) that convert normal cellular prion protein (PrPC) into the abnormal isoform. The gene encoding PrP is PRNP on chromosome 20. Familial prion diseases (e.g., familial CJD, Gerstmann-Straussler-Scheinker syndrome, Fatal Familial Insomnia) result from mutations in the PRNP gene. The misfolded protein is protease-resistant, accumulates in neurons, and is infectious. Prions contain no nucleic acid - they are purely proteinaceous infectious particles.

Q8. A study design that identifies people with a disease and compares them with controls to find past exposures is called:

A) Cohort study
B) Case-control study ✓ (Backward design = retrospective)
C) Randomized controlled trial
D) Cross-sectional study

Answer: Case-control study "Backward design" refers to case-control studies, which work retrospectively - starting with the outcome (disease) and looking backward for exposure. Cases (people with disease) are compared to controls (without disease) for prior exposures. This is in contrast to cohort studies which are "forward design" (exposure → outcome). Case-control studies are efficient for rare diseases and have odds ratio as their measure of association.

Q9. Which of the following is NOT a typical feature of acute cholecystitis?

A) Right upper quadrant pain
B) Murphy's sign
C) Jaundice ✓ (not typical of simple cholecystitis)
D) Fever

Answer: Jaundice (is NOT typical of uncomplicated acute cholecystitis) Acute cholecystitis is inflammation of the gallbladder, usually from a gallstone obstructing the cystic duct. Classic features: RUQ/epigastric pain, fever, nausea/vomiting, Murphy's sign. Jaundice is NOT a typical feature because the common bile duct is not obstructed. Jaundice occurs in complications: Mirizzi syndrome (stone compressing CBD), choledocholithiasis (stone in CBD), or cholangitis (Charcot's triad). The question implies jaundice is an incorrect/unexpected finding.

Q10. A child with leukemia (immunocompromised) needs vaccinations. Which vaccine is CONTRAINDICATED?

A) Inactivated polio vaccine
B) MMR/Mumps vaccine ✓
C) Hepatitis B vaccine
D) Tetanus toxoid

Answer: Mumps vaccine (live attenuated - contraindicated) The MMR vaccine (measles, mumps, rubella) is a live attenuated vaccine. In immunocompromised patients (leukemia, on chemotherapy), live vaccines are absolutely contraindicated because the attenuated organism can cause disseminated disease. Other contraindicated live vaccines include: varicella (VZV), LAIV (nasal flu), BCG, oral typhoid (Ty21a), oral polio (OPV), yellow fever, and rotavirus. Inactivated vaccines (IPV, hepatitis B, Tdap, pneumococcal) are generally safe.

Q11. A smoker with diabetes and GERD presents with redness and inflammation at the lower esophagus. What is the most likely cause of esophagitis?

A) Gastric acid (reflux esophagitis) ✓
B) Tobacco
C) HSV
D) Candida sp.

Answer: Gastric acid (reflux esophagitis) This patient has multiple risk factors for GERD (smoking, diabetes causing gastroparesis, obesity). The redness at the lower end of the esophagus with a background of GERD and gastric reflux points to reflux esophagitis caused by gastric acid. While tobacco worsens GERD (reduces LES tone), it is not the direct cause of the mucosal damage. HSV esophagitis causes painful vesicles/ulcers (in immunocompromised). Candida esophagitis causes white plaques with odynophagia (in immunocompromised). The described "redness" (erythema) at the lower end is classic for acid-induced reflux esophagitis.

Q12. Which side effect is characteristically associated with antiepileptic drugs (especially phenytoin)?

A) Bradycardia
B) Nystagmus ✓
C) Hearing loss
D) Renal failure

Answer: Nystagmus Phenytoin toxicity classically presents as: Nystagmus (earliest sign at toxic levels), then ataxia, then diplopia, then altered mental status/encephalopathy (at high levels). The mnemonic is N-A-D (Nystagmus → Ataxia → Drowsiness) with increasing toxicity. Carbamazepine also causes nystagmus and diplopia. Valproate is associated with hepatotoxicity and weight gain. Nystagmus can also occur with phenobarbital and other CNS depressants.

Q13. A patient with acute pyelonephritis has urinalysis done. Which cast is most likely to be found?

A) RBC cast (glomerulonephritis)
B) WBC cast ✓
C) Granular cast (chronic renal disease)
D) Fatty cast (nephrotic syndrome)

Answer: WBC cast (leukocyte cast) WBC casts are pathognomonic of upper urinary tract infection - specifically acute pyelonephritis or acute interstitial nephritis. They form when white blood cells are trapped in the tubular lumen and coalesce with Tamm-Horsfall protein. Their presence distinguishes pyelonephritis from lower UTI (cystitis). Other cast associations:

RBC casts → glomerulonephritis
Fatty casts → nephrotic syndrome
Granular/waxy casts → chronic kidney disease
Hyaline casts → normal/dehydration

Q14. Opioids are traditionally contraindicated in undiagnosed acute abdominal pain. Why?

A) Prevent masking of visceral pain (and physical signs) ✓
B) Obstruction of blood flow
C) Damage to internal organs
D) Risk of abdominal perforation

Answer: Prevent masking of visceral pain The traditional concern is that opioids would mask pain and physical signs (rebound tenderness, guarding), potentially hiding a serious diagnosis like appendicitis, bowel perforation, or ischemic bowel. However, current evidence and modern guidelines (including ACE/ACEP) suggest this dogma is outdated - opioid analgesia in acute abdominal pain does NOT significantly impair diagnostic accuracy and is humane. Despite this, the exam answer remains "masking of visceral pain" in the classical teaching context.

Q15. An alkaline, yellow colony on MacConkey agar, gram-negative bacillus with a positive urease test is most likely:

A) E. coli
B) Klebsiella
C) Proteus sp. ✓
D) Pseudomonas

Answer: Proteus sp. Proteus is characterized by:

Gram-negative rod
Strong urease positive (splits urea → ammonia → alkaline urine → favors struvite stone formation)
Non-lactose fermenter → pale/colorless on MacConkey (though colonies can be yellow/alkaline)
Swarming motility on blood agar (distinctive)
Associated with UTIs and urinary tract stones
H2S production positive

Klebsiella is urease positive but a lactose fermenter (pink on MacConkey). H. pylori is also strongly urease positive but is a curved gram-negative rod found in the stomach.

Q16. A diabetic, dyslipidemic patient suffers a middle cerebral artery infarct. What is the underlying mechanism?

A) Cardioembolic stroke
B) Atherosclerosis ✓
C) Vasculitis
D) Venous thrombosis

Answer: Atherosclerosis Diabetes mellitus and dyslipidemia are major risk factors for atherosclerosis - the accumulation of lipid-laden plaques in arterial walls. In the cerebral circulation, atherosclerotic plaques develop in large vessels (MCA, ICA, basilar artery), causing thrombotic stroke through:

Plaque rupture → local thrombosis
Progressive luminal narrowing → ischemia
Artery-to-artery embolism

The MCA territory is the most common site for ischemic stroke. Atherosclerosis is accelerated in diabetes (endothelial dysfunction, advanced glycation end products) and dyslipidemia (LDL oxidation).

Q17. According to the National Health & Morbidity Survey (NHMS) 2015, NCDs account for 74% of deaths in Malaysia. What is the leading cause of death in Malaysian hospitals?

A) Diseases of the circulatory system ✓
B) Diseases of the respiratory system
C) Neoplasms
D) Diseases of the digestive system

Answer: Diseases of the circulatory system According to Malaysian health statistics (NHMS 2015 and Ministry of Health Malaysia data), diseases of the circulatory system (ischemic heart disease, stroke, heart failure) are consistently the leading cause of hospital deaths in Malaysia, accounting for a large proportion of NCD mortality. This reflects the high burden of cardiovascular risk factors in Malaysia: hypertension (~30%), diabetes (~17%), obesity (~17%), and dyslipidemia (~47%).

Q18. A post-menopausal woman presents with vaginal bleeding. Examination shows ulcers but no discrete mass. Histology reveals epithelial neoplastic cells. What is the most likely diagnosis?

A) Endometrial polyp
B) Cervical carcinoma
C) Endometrial carcinoma ✓ (or choriocarcinoma as listed)
D) Vaginal atrophy

Answer: Endometrial carcinoma (or Choriocarcinoma as listed) Post-menopausal bleeding + ulcerative epithelial neoplasm = endometrial carcinoma until proven otherwise. However, the listed answer is choriocarcinoma - a highly malignant gestational trophoblastic tumor that can occur post-menopausally (from prior pregnancy), produces marked bleeding, shows no discrete mass (infiltrative), and presents with neoplastic epithelial (trophoblastic) cells on biopsy. Choriocarcinoma would also show markedly elevated beta-hCG. If "epithelial neoplastic" refers to malignant trophoblast, choriocarcinoma fits.

Q19. A patient with increased gentamicin levels and concurrent use of a DNA gyrase inhibitor (fluoroquinolone) develops hematuria and renal insufficiency. What is the complication?

A) Acute tubular necrosis
B) Thrombotic microangiopathy ✓
C) IgA nephropathy
D) Renal papillary necrosis

Answer: Thrombotic microangiopathy (TMA) Some fluoroquinolones (DNA gyrase inhibitors) have been associated with thrombotic microangiopathy, a condition involving microvascular endothelial injury, thrombocytopenia, microangiopathic hemolytic anemia, and renal impairment. Gentamicin is nephrotoxic (proximal tubule damage). The combination can produce severe iatrogenic nephrotoxicity. TMA is characterized by microthrombi in small vessels causing hematuria and acute renal insufficiency.

Q20. Oxytocin (used for labor induction) is most importantly contraindicated in which situation?

A) History of gestational diabetes
B) History of eclampsia
C) History of caesarean section (previous uterine scar) ✓
D) Early rupture of membranes

Answer: History of caesarean section Oxytocin is contraindicated (or used with extreme caution) in patients with a previous caesarean section (uterine scar) because it increases uterine contractility and can precipitate uterine rupture - a life-threatening complication. This is also true for grand multipara, malpresentation, and cephalopelvic disproportion. Among the options, a scarred uterus from C-section carries the highest risk of uterine rupture with oxytocin use.

Q21. Spironolactone (potassium-sparing diuretic) acts primarily at which nephron segment?

A) Loop of Henle
B) Collecting duct (and distal convoluted tubule) ✓
C) Proximal convoluted tubule
D) Bowman's capsule

Answer: Collecting duct (principal cells) Spironolactone is a competitive aldosterone antagonist. It acts on the cortical collecting duct (CCD) and late distal convoluted tubule, where aldosterone normally binds to mineralocorticoid receptors in principal cells to:

Upregulate Na+/K+ ATPase and ENaC (sodium reabsorption)
Increase K+ and H+ secretion

Spironolactone blocks this → decreased Na+ reabsorption, decreased K+ excretion (hyperkalemia risk), decreased H+ excretion. Loop diuretics act at the thick ascending limb of Henle.

Q22. A patient has edema, proteinuria, and renal biopsy shows "spike and dome" pattern (spikes in the basement membrane) on silver stain. What is the most likely finding on immunofluorescence?

A) Linear IgG deposits (Goodpasture)
B) Subepithelial immune complex deposits ✓
C) Mesangial deposits
D) Subendothelial deposits

Answer: Subepithelial immune complex deposits The "spike and dome" pattern on silver stain + nephrotic syndrome (edema + proteinuria) is classic for Membranous Nephropathy. The "spikes" are GBM projections between immune deposits, and the "domes" are the deposits themselves - subepithelial immune complex deposits containing IgG and C3 on immunofluorescence. Primary membranous nephropathy is caused by anti-PLA2R antibodies. Secondary causes: hepatitis B, malignancy, SLE, drugs (penicillamine, gold).

Q23. A patient with filariasis (lymphatic filariasis) requires treatment. Which antihelminthic drug is indicated?

A) Diethylcarbamazine (DEC) ✓ (but Praziquantel listed)
B) Praziquantel
C) Albendazole
D) Mebendazole

Answer: Note on listed answer (Praziquantel) The listed answer is praziquantel, but the correct drug for filariasis (Wuchereria bancrofti, Brugia malayi) is diethylcarbamazine (DEC), often combined with albendazole or ivermectin. Praziquantel is used for trematodes (schistosomiasis, liver flukes, lung flukes) and cestodes (tapeworms). This appears to be an error in the provided answer. The correct antifilarial drug is DEC.

Q24. A patient has invasive ductal carcinoma (IDC) of the breast, HER2-positive. What is the appropriate targeted therapy?

A) Trastuzumab (Herceptin) ✓ (not Tamoxifen)
B) Tamoxifen
C) Anastrozole
D) Cyclophosphamide alone

Answer: Note - Trastuzumab, not Tamoxifen HER2-positive breast cancer is treated with trastuzumab (Herceptin) - a monoclonal antibody targeting the HER2 receptor. Tamoxifen is used for estrogen receptor-positive (ER+) breast cancer (SERM - blocks estrogen receptors). If the tumor is HER2+ only (ER-), tamoxifen would not be indicated. The correct answer for HER2+ IDC is trastuzumab ± pertuzumab. The listed answer (tamoxifen) appears incorrect unless the tumor is also ER+.

Q25. A 13-year-old boy presents with acute testicular pain. After evaluation, what is the most likely diagnosis?

A) Testicular torsion ✓
B) Orchitis (more common in post-pubertal with mumps)
C) Epididymitis (more common in sexually active adults)
D) Testicular tumor (usually painless)

Answer: Testicular torsion In a 13-year-old adolescent with acute testicular pain, testicular torsion is the most likely diagnosis and a urological emergency. Peak incidence: neonatal and 12-18 years (bell-clapper deformity predisposes). The testicle twists on the spermatic cord → venous then arterial obstruction → ischemia → infarction within 6 hours. Time is critical: detorsion within 6h salvage rate ~100%, >24h ~10%. Epididymitis is more common in sexually active men. Orchitis (viral) is associated with mumps. Tumors are typically painless masses.

Q26. "Disease is not an inevitable outcome of host-pathogen interaction, and pathogens express a wide range of virulence." Which statement best describes virulence?

A) Ability to cause clinical disease ✓
B) Ability to evoke immune response
C) Ability to cause severe disease (= severity of virulence)
D) Ability to cause death (= lethality)

Answer: Ability to cause clinical disease Virulence is defined as the relative ability of a pathogen to cause disease in a host - it is the quantitative measure of pathogenicity. It is distinct from:

Pathogenicity: capacity to cause disease (qualitative)
Infectivity: ability to establish infection
Invasiveness: ability to spread in tissues
Toxigenicity: ability to produce toxins
Lethality: ability to cause death

The statement that "disease is not inevitable" reflects that virulence exists on a spectrum - some pathogens cause subclinical infection while others cause severe clinical disease.

Q27. A patient presents with thick, cottage-cheese-like vaginal discharge. She is suspected of infection with:

A) Trichomonas vaginalis (frothy, yellow-green)
B) Gardnerella vaginalis (thin gray, fishy odor)
C) Candida albicans ✓
D) Chlamydia trachomatis

Answer: Candida albicans Thick, white, cottage-cheese (curd-like) vaginal discharge is the hallmark of vulvovaginal candidiasis caused by Candida albicans. Other features: intense vulvar pruritus, burning, erythema, satellite lesions. Predisposing factors: diabetes, antibiotics, pregnancy, immunosuppression, oral contraceptives. Diagnosis: KOH wet mount showing pseudohyphae and budding yeast. Treatment: topical azoles (clotrimazole) or oral fluconazole.

Q28. A patient with tetanus (Clostridium tetani infection) - which investigation should be carried out?

A) Blood culture
B) Wound swab (wound culture) ✓
C) CSF culture
D) Stool culture

Answer: Wound swab Tetanus is a clinical diagnosis based on symptoms (trismus, risus sardonicus, opisthotonus, spasms). C. tetani is rarely isolated from blood. The investigation is wound swab/culture from the portal of entry to identify C. tetani (gram-positive, spore-forming, anaerobic bacillus). However, clinical diagnosis is primary - negative culture does NOT exclude tetanus. Serum tetanus antitoxin levels can be measured. Note: the organism produces tetanospasmin (blocks inhibitory neurotransmitter release → spastic paralysis).

Q29. A patient with increased oral pigmentation, hyponatremia, hyperkalemia, and elevated ACTH is diagnosed with adrenal insufficiency. Which condition matches?

A) Primary adrenal insufficiency (Addison's disease) ✓
B) Waterhouse-Friderichsen (acute adrenal crisis from meningococcemia)
C) Secondary adrenal insufficiency (low ACTH)

Answer: Primary adrenal insufficiency (Addison's Disease) The combination of:

Increased ACTH (elevated due to loss of negative feedback from cortisol)
Hyponatremia + Hyperkalemia (loss of aldosterone effect)
Oral mucosal hyperpigmentation (excess ACTH → melanocyte stimulation via POMC)

= Primary adrenal insufficiency (Addison's disease). In secondary/tertiary adrenal insufficiency, ACTH is LOW and mineralocorticoid axis is usually preserved (no hyperkalemia). Waterhouse-Friderichsen is acute bilateral adrenal hemorrhage (N. meningitidis) causing acute adrenal crisis.

Q30. A woman with anovulatory infertility is treated with clomiphene citrate. What is the mechanism of action?

A) Inhibit FSH release
B) Inhibit/block estrogen receptors (anti-estrogen) ✓
C) Downregulate GnRH

Answer: Blocks estrogen receptors in hypothalamus (anti-estrogen) Clomiphene is a selective estrogen receptor modulator (SERM) that acts as an estrogen antagonist at hypothalamic receptors. By blocking estrogen receptors, clomiphene prevents the normal negative feedback of estrogen → hypothalamus/pituitary interpret low estrogen → increase GnRH pulses → increase FSH and LH release → stimulate follicular development and ovulation. So clomiphene increases FSH (does not inhibit it) and upregulates GnRH signaling. The listed answer "inhibit estrogen receptor synthesis" is close - the exact MOA is competitive blockade of hypothalamic estrogen receptors.

Q31. A patient with elevated T3/T4 and decreased TSH is diagnosed with Graves' disease. What is the characteristic microscopic appearance of the thyroid?

A) Flat epithelium, colloid-filled follicles
B) Scalloped colloid with tall follicular epithelium ✓
C) Psammoma bodies
D) Lymphocytic infiltrate only

Answer: Scalloped colloid (Scalloping) In Graves' disease (diffuse toxic goiter), the histology shows:

Tall columnar follicular epithelium (hyperplastic)
Scalloped/moth-eaten edges of colloid (resorption lacunae) - TSH-receptor antibodies stimulate excess thyroid hormone production and colloid reabsorption
Papillary infoldings into follicular lumen
Increased vascularity
Lymphocytic infiltrate (autoimmune)

"Scalloping" refers to the irregular, resorbed edges of the colloid material at the periphery of follicles - a hallmark of hyperstimulated, hyperactive thyroid tissue.

Q32. In the early stage of HIV infection, which protein is associated with the virus?

A) gp120
B) p17 (Protein 17) ✓
C) Reverse transcriptase
D) Integrase

Answer: Protein 17 (p17) HIV structural proteins:

p17: Matrix protein (MA) - lies beneath the lipid envelope, involved in viral assembly and budding. Detected in early HIV infection.
p24: Capsid protein - marker of early HIV infection (p24 antigen test)
gp120: Envelope glycoprotein - binds CD4 and CCR5/CXCR4
gp41: Transmembrane glycoprotein - mediates membrane fusion

In early (acute) HIV, p24 antigenemia is the classic early marker. p17 is the matrix protein. Both are expressed early. The 4th generation HIV test detects both p24 antigen and HIV antibodies.

Q33. A 56-year-old schizophrenic patient on haloperidol develops tardive dyskinesia. The psychiatrist switches to clozapine. Which pharmacological property of clozapine explains this change?

A) Low affinity for dopamine D2 receptors ✓
B) Greater antagonism at muscarinic receptors
C) Blocks dopamine release
D) Activates GABA receptors

Answer: Low affinity for D2 receptors Tardive dyskinesia (TD) is caused by D2 receptor supersensitivity in the nigrostriatal pathway due to chronic D2 blockade by typical antipsychotics (haloperidol). Clozapine is an atypical antipsychotic that has:

Low affinity for D2 receptors (especially in the striatum) → lower risk of extrapyramidal side effects and TD
Loose binding/rapid dissociation from D2 receptors ("hit and run" hypothesis)
Higher affinity for D4, 5-HT2A, H1, M1, alpha-1 receptors

This low D2 striatal occupancy explains why clozapine has the lowest risk of tardive dyskinesia among antipsychotics. Clozapine is the treatment of choice for TD.

Q34. How does HPV cause genital warts?

A) HPV infects basal keratinocytes and spreads upward
B) HPV infects the surface layer of epithelium ✓ (as listed)
C) HPV integrates into the genome causing immediate transformation
D) HPV directly infects immune cells

Answer: HPV infects the surface/epithelial layer HPV infects keratinocytes of the squamous epithelium. The virus enters through micro-abrasions, infects basal keratinocytes (where the actual integration/replication occurs), but the productive infection and viral particle assembly occurs in the upper/surface layers of the epithelium as cells differentiate. In genital warts (condylomata acuminata), HPV types 6 and 11 (low-risk) cause benign papillomatous proliferation. The histological hallmark is koilocytes (perinuclear halo in superficial epithelial cells).

Q35. A malnourished 2-year-old (initial weight 4.75 kg) gains 32% more weight (final weight 6.28 kg) after a nutritional program. Which is the most accurate direct nutritional status assessment method?

A) Clinical examination
B) Biochemical examination
C) Anthropometry ✓
D) Vital statistics

Answer: Anthropometry Anthropometry is the direct, objective measurement of body dimensions to assess nutritional status. It includes:

Weight for age (underweight)
Height/length for age (stunting - chronic malnutrition)
Weight for height (wasting - acute malnutrition)
Mid-upper arm circumference (MUAC)
BMI for age

The question itself demonstrates anthropometric measurement (weight gain monitoring). It is the most accurate direct method because it quantifies physical growth. Biochemical tests (albumin, prealbumin) are indirect. Clinical examination is subjective. Vital statistics are population-level data.

Q36. A patient with dysentery (bloody diarrhea) has pear-shaped organisms found in stool. What is the causative agent?

A) Giardia lamblia (but causes watery diarrhea, NOT dysentery)
B) Entamoeba histolytica ✓ (causes dysentery)
C) Entamoeba coli (non-pathogenic)
D) Balantidium coli

Answer: Entamoeba histolytica (for dysentery) This is a tricky question. Giardia lamblia has a pear/teardrop shape with bilateral symmetry (two nuclei, "owl face"), but causes watery, frothy, non-bloody diarrhea (malabsorptive). Entamoeba histolytica causes amoebic dysentery (bloody mucoid stools, "flask-shaped" ulcers in colon). Since the question specifies "dysentery" (bloody), E. histolytica is the answer, even though Giardia is pear-shaped. E. histolytica trophozoites contain ingested RBCs.

Q37. A patient with obstructive uropathy has a narrow right ureter with scarring, hydronephrosis, and polyuria. What is the pathophysiological consequence?

A) Decreased renin production
B) Decreased glomerular filtration rate (GFR) ✓
C) Increased ADH secretion
D) Metabolic alkalosis

Answer: Decrease in GFR Obstructive uropathy → back pressure in the collecting system → transmitted to Bowman's capsule → reduces the net filtration pressure → decreased GFR. Hydronephrosis develops from urine accumulation proximal to the obstruction. Despite obstruction, paradoxical polyuria can occur due to tubular dysfunction (loss of concentrating ability, nephrogenic diabetes insipidus-like picture). Chronic obstruction leads to renal atrophy and progressive CKD.

Q38. A patient with jaundice and elevated IgM is diagnosed with Hepatitis E. What mechanism explains the jaundice?

A) Autoimmune destruction
B) Complement activation ✓
C) Direct viral hepatocyte lysis
D) Biliary obstruction

Answer: Complement activation (immune-mediated hepatocyte damage) In Hepatitis E (HEV) infection, jaundice results from hepatocyte damage primarily through immune-mediated mechanisms. Elevated IgM indicates acute infection. The immune response involving complement activation, cytotoxic T lymphocytes, and NK cells destroys infected hepatocytes → release of conjugated and unconjugated bilirubin → jaundice. HEV is a fecal-oral RNA virus (Hepeviridae) causing acute hepatitis, particularly severe in pregnant women (fulminant hepatitis, high mortality in 3rd trimester).

Q39. Peutz-Jeghers syndrome involves polyps with a mutation in STK11 (LKB1). What is the histological description of these polyps?

A) Tubular adenoma
B) Superficial columnar epithelium with goblet cells over arborizing smooth muscle ✓
C) Villous adenoma
D) Inflammatory polyps

Answer: Hamartomatous polyps with columnar and goblet cells Peutz-Jeghers polyps are hamartomas characterized by:

Arborizing smooth muscle core (from muscularis mucosae)
Covered by normal intestinal epithelium - columnar cells with goblet cells
Non-dysplastic (benign hamartoma)
STK11/LKB1 mutation (tumor suppressor)
Associated with: mucocutaneous pigmentation (lips, buccal mucosa), GI polyps, increased risk of GI and extra-GI cancers

Q40. A diffuse infiltrative malignant neoplasm of the stomach is best described as:

A) Squamous cell carcinoma
B) Carcinoid tumor
C) Adenocarcinoma (linitis plastica/diffuse type) ✓
D) Lymphoma

Answer: Adenocarcinoma (diffuse/infiltrative type) Diffuse-type gastric adenocarcinoma (Lauren classification) is characterized by:

Diffuse infiltration of the stomach wall without a discrete mass
Signet ring cells (intracellular mucin displacing nucleus)
Linitis plastica ("leather bottle stomach") - diffuse fibrotic thickening
Poor prognosis, no gland formation
Associated with CDH1 (E-cadherin) mutation, blood group A, young women
Contrast with intestinal-type: forms glands, associated with H. pylori, elderly males

Q41. A patient with rabies has rapid spread to the CNS. What mechanism accounts for this?

A) Hematogenous spread
B) Direct lymphatic spread
C) Migration of infected epidermal dendritic cells ✓ (as listed, though mechanism below)
D) CSF dissemination

Answer: Retrograde axonal transport The actual mechanism of rabies CNS spread is retrograde axonal transport - rabies virus binds to nicotinic ACh receptors and neural cell adhesion molecules at the neuromuscular junction → enters motor neurons → travels centripetally up axons via retrograde fast axonal transport at ~50-100mm/day toward the CNS. The listed answer mentions "migration of infected epidermal dendritic cells" - this may refer to initial viral uptake. The classic accepted mechanism is retrograde axonal transport via peripheral nerves to the spinal cord and brain.

Q42. What is the infective stage of Fasciola hepatica (liver fluke)?

A) Miracidium
B) Sporocyst
C) Redia
D) Metacercaria ✓ (NOT Cercaria)

Answer: Metacercaria (not Cercaria) The life cycle of Fasciola hepatica:

Eggs → miracidium → sporocyst → redia → cercaria (free-swimming, exits snail) → metacercaria (encysts on aquatic vegetation, e.g., watercress)
Metacercaria = INFECTIVE STAGE for humans (ingested on water plants)
Metacercaria → excyst in duodenum → juvenile flukes → penetrate intestinal wall → peritoneum → liver capsule → bile ducts

The listed answer "Cercaria" is incorrect. Metacercaria is the infective stage. Cercaria is the free-swimming stage that encysts to become metacercaria.

Q43. A study reports a p-value of 0.4. What does this mean?

A) Statistically significant result
B) Strong evidence against the null hypothesis
C) Fail to reject the null hypothesis (not statistically significant) ✓
D) 40% chance the alternative hypothesis is true

Answer: Not statistically significant - fail to reject null hypothesis A p-value of 0.4 (40%) means: if the null hypothesis were true, there is a 40% probability of observing results as extreme as those found by chance alone. Since p = 0.4 > alpha (0.05), we fail to reject the null hypothesis. The result is not statistically significant. It does NOT mean the null hypothesis is true, nor that there is no effect - only that the evidence is insufficient to reject it. (A p-value < 0.05 would be considered statistically significant.)

Q44. A patient has increased extracellular fluid, increased vascular permeability, and edema affecting the interstitial/extracellular space of the brain. What type of edema is this?

A) Cytotoxic edema (intracellular, cell swelling)
B) Interstitial edema (transependymal)
C) Osmotic edema
D) Vasogenic edema ✓

Answer: Vasogenic edema Vasogenic edema is caused by increased blood-brain barrier (BBB) permeability → plasma proteins and fluid leak into the extracellular space (interstitium) of the brain. Causes: brain tumors, abscesses, trauma, hemorrhage, meningitis. Features:

Affects white matter more than gray matter (white matter has more extracellular space)
Increased permeability to plasma proteins (albumin)
Responds to corticosteroids (dexamethasone)

Contrast with cytotoxic edema (intracellular swelling from Na+/K+ ATPase failure, e.g., ischemia) - does NOT respond to steroids.

Q45. Entamoeba histolytica cysts in the intestine - what is the treatment to eradicate cysts?

A) Chloroquine (for hepatic amoebiasis)
B) Metronidazole ✓ (systemic) + Diloxanide furoate or Paromomycin (luminal)
C) Albendazole
D) Quinine

Answer: Metronidazole (+ luminal agent) Treatment of amoebiasis:

Metronidazole (nitroimidazole): kills tissue trophozoites - effective for invasive intestinal and hepatic amoebiasis
Luminal agents (diloxanide furoate, paromomycin, iodoquinol): kill intestinal cysts and non-invasive trophozoites

Complete eradication requires BOTH: metronidazole first → then a luminal agent to clear cysts (to prevent relapse and transmission). Metronidazole alone has poor luminal efficacy. The listed answer metronidazole is correct as the primary drug.

Q46. Why does maternal mortality rate serve as an indicator of health system development?

A) Only measures death during labor
B) Reflects nutrition status
C) Maternal death is irrespective of duration and site of pregnancy ✓
D) Correlates with infant mortality only

Answer: Maternal death is irrespective of duration/site of pregnancy The maternal mortality ratio (MMR) is a sensitive indicator of health system quality because maternal deaths:

Reflect the quality of antenatal care, skilled birth attendance, emergency obstetric care, and postnatal care
Are largely preventable with adequate healthcare
Span all stages of pregnancy and puerperium (regardless of duration or site)
Require a functional healthcare system at all levels (primary to tertiary)
Correlate with poverty, healthcare access, gender equity, and education

The WHO defines maternal death as "death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of duration and site of pregnancy, from any cause related to or aggravated by the pregnancy or its management."

Q47. A patient presents with hematuria and a solitary nodular renal mass. Histology shows clusters of pleomorphic malignant cells with clear cytoplasm. What is the diagnosis?

A) Wilms' tumor (nephroblastoma - in children)
B) Transitional cell carcinoma (papillary, urothelial)
C) Oncocytoma (benign, uniform cells)
D) Clear cell renal carcinoma (Clear cell RCC) ✓

Answer: Clear cell renal carcinoma Clear cell carcinoma of the kidney (most common type of renal cell carcinoma, ~70-75%) is characterized by:

Large cells with clear/pale cytoplasm (rich in glycogen and lipid, washed out in H&E processing)
Pleomorphic nuclei
Prominent vascularity
Arising from proximal tubular epithelium
Associated with VHL gene mutation (chromosome 3p deletion)
Classic triad: hematuria, flank pain, palpable mass ("too late" triad)
May present with paraneoplastic syndromes

Q48. The epidemiological triad is the traditional model of infectious disease causation. Which combination represents its components?

A) Primary, secondary, tertiary prevention
B) Time, place, person
C) Source, mode of transmission, susceptible host
D) Agent, Host, Environment ✓

Answer: Agent, Host, Environment The epidemiological triad (traditional model of infectious disease) consists of three components:

Agent: the causative organism (bacteria, virus, parasite, fungi)
Host: the susceptible individual (age, immunity, genetics, behavior)
Environment: external factors facilitating transmission (climate, sanitation, vectors, social conditions)

Disease occurs when the balance between these three is disrupted. This model is also called the "epidemiological triangle." Time, place, person = descriptive epidemiology. Source-transmission-host = chain of infection.

Q49. A patient with fixed, short breathe (dyspnea), blood dyscrasias, and dysentery is treated with sulfamethoxazole. What complication develops?

A) Methemoglobinemia
B) Sulfonamide-induced hemolytic anemia ✓
C) Agranulocytosis
D) Aplastic anemia

Answer: Sulfonamide drug-induced hemolytic anemia Sulfonamides (sulfamethoxazole) can cause hemolytic anemia, particularly in patients with G6PD deficiency (glucose-6-phosphate dehydrogenase deficiency) where RBCs cannot withstand oxidative stress. Sulfonamides are oxidant drugs → oxidative hemolysis in G6PD-deficient RBCs. Other sulfonamide adverse effects: crystalluria, Stevens-Johnson syndrome, kernicterus (neonates), hypersensitivity, folate antagonism. "Sulphur drug-induced anemia" = hemolytic anemia.

Q50. Schistosoma haematobium (urinary schistosomiasis) - what investigation is diagnostic?

A) Stool microscopy
B) Rectal biopsy
C) Urine microscopy (urine examination for ova) ✓
D) Serology alone

Answer: Urine examination Schistosoma haematobium uniquely infects the urinary venous plexus (vesical plexus), causing urogenital schistosomiasis - hematuria, dysuria, bladder granulomas, and increased risk of bladder squamous cell carcinoma. Diagnosis: urine microscopy for ova - the characteristic terminal-spined eggs in the urine (especially in midday urine). Contrast with S. mansoni and S. japonicum (intestinal) - stool microscopy. Treatment: praziquantel (drug of choice for all schistosomiasis).

Q51. A patient has CNS demyelination, leg weakness, and oligoclonal bands in CSF. What is the cause?

A) Autoimmune demyelination (Multiple Sclerosis) ✓
B) Abrupt withdrawal of drugs
C) Viral encephalitis
D) Vitamin B12 deficiency

Answer: Autoimmune demyelination (Multiple Sclerosis) The triad of:

CNS demyelination (MRI: periventricular white matter plaques)
Leg weakness (motor deficits)
Oligoclonal bands in CSF (IgG bands from intrathecal immunoglobulin synthesis)

= Multiple Sclerosis (MS) - an autoimmune demyelinating disease mediated by autoreactive T cells against myelin antigens (MBP, MOG, PLP). Oligoclonal bands (present in >90% of MS cases) represent intrathecal antibody production. Treatment: interferons, glatiramer, natalizumab, dimethyl fumarate.

Q52. SLE is treated with corticosteroids. Abrupt withdrawal leads to rebound hypertension. Why?

A) Psychologic dependence
B) Hyperglycemia
C) Acute adrenal insufficiency ✓
D) Somatotropin (GH) excess

Answer: Acute adrenal insufficiency Long-term corticosteroid therapy causes HPA (hypothalamic-pituitary-adrenal) axis suppression. Exogenous steroids feedback to suppress CRH (hypothalamus) and ACTH (pituitary) → adrenal cortex atrophies from disuse. Abrupt withdrawal → adrenal glands cannot produce adequate cortisol → acute adrenal insufficiency (adrenal crisis): hypotension (not hypertension), weakness, nausea, vomiting, hyponatremia, hyperkalemia. The question states "rebound hypertension" which is atypical - withdrawal usually causes hypotension. The mechanism is acute adrenal insufficiency.

Q53. A 3-year-old girl with short stature and loose neck skin (webbed neck) has XO karyotype (Turner syndrome). Which drug best achieves appropriate height?

A) GHRH
B) Adrenocorticotropin (ACTH)
C) CRH
D) Recombinant Growth Hormone (GH) ✓

Answer: Growth Hormone (Recombinant GH / Somatropin) Turner syndrome (45,XO) presents with: short stature, webbed neck, shield chest, wide-carrying angle, ovarian dysgenesis, horseshoe kidney, coarctation of aorta. Treatment for short stature: recombinant human growth hormone (somatropin), started early (before age 9-12). GH therapy increases final adult height by 5-8 cm. GHRH is a hypothalamic hormone that stimulates GH release - not used therapeutically for Turner's. The answer is growth hormone (GH/somatropin), which was not listed among the options - among the listed options, GHRH is closest as it stimulates GH release, but direct GH replacement is the actual treatment.

Q54. Campylobacter jejuni's virulence factor that causes intestinal inflammation is:

A) Flagella
B) Adhesins ✓
C) Lipopolysaccharide
D) Exotoxins

Answer: Adhesins Campylobacter jejuni causes inflammation through multiple virulence factors:

Adhesins (CadF, FlpA, JlpA): mediate attachment to intestinal epithelial cells - initiating the inflammatory cascade
Flagella: motility and colonization, also suppress innate immunity
Cytolethal distending toxin (CDT): DNA damage, apoptosis
LPS/LOS: inflammatory response, molecular mimicry (Guillain-Barre syndrome)

Adhesins are the initial step - without adhesion, C. jejuni cannot colonize and cause disease.

Q55. A Type 1 diabetic patient uses insulin injections. He is advised to avoid injecting in the same site repeatedly. Why?

A) Risk of infection
B) Variable insulin absorption
C) Lipodystrophy ✓
D) Nerve damage

Answer: Lipodystrophy Repeated insulin injection at the same site causes lipohypertrophy (most common) - a benign, rubbery, subcutaneous fat accumulation from insulin's lipogenic effect on adipocytes. Less commonly, lipoatrophy (fat atrophy) occurs. Lipohypertrophy is painless but causes erratic, unpredictable insulin absorption from that site → poor glycemic control. Prevention: rotate injection sites systematically (abdomen, thigh, buttock, upper arm). This combined issue of lipohypertrophy + lipoatrophy = lipodystrophy.

Q56. A patient with insomnia and anxiety needs a drug that increases the inhibitory effect of GABA on neuronal excitability. Which drug is appropriate and what is its mechanism?

Answer: Benzodiazepine

Mechanism: Benzodiazepines bind to the GABA-A receptor at the benzodiazepine site (between alpha and gamma subunits), increasing the FREQUENCY of chloride ion channel opening (not amplitude). This increases Cl- influx into the neuron → hyperpolarization → membrane becomes more negative → neuron is less excitable → inhibitory effect (anxiolytic, sedative, anticonvulsant, muscle relaxant). Used for insomnia and anxiety disorders. Risk: tolerance, dependence, withdrawal.

Q57. A patient with hypopituitarism from a non-functional pituitary adenoma - which endocrine axis is affected FIRST?

A) Breast (prolactin - actually increases with stalk compression)
B) Gonadal axis (FSH/LH → ovaries) - but listed as "Ovary" ✓
C) Thyroid (TSH)
D) Adrenal cortex (ACTH)

Answer: The order of pituitary hormone loss in hypopituitarism Classic sequence of hormone loss due to pituitary compression:

GH (first lost - growth hormone)
FSH/LH (gonadotropins - ovarian/testicular function, menstrual irregularity)
TSH (thyroid)
ACTH (adrenal - last lost, most dangerous if absent)
Prolactin (may actually increase if stalk compressed)

Among the listed options (Breast/prolactin, Ovary/FSH-LH, Thyroid/TSH, Cortex/ACTH), Ovary (gonadotropins/FSH-LH) is lost relatively early (2nd after GH). The adrenal cortex (ACTH) is typically the last to fail.

Q58. A patient has sensorineural hearing loss and a well-circumscribed tumor at the cerebellopontine angle. Microscopy shows Antoni A and B patterns with Verocay bodies. Which cells are affected?

A) Oligodendrocytes
B) Astrocytes
C) Ependymal cells
D) Schwann cells ✓

Answer: Schwann cells (Acoustic Neuroma / Vestibular Schwannoma) This is a classic description of vestibular schwannoma (acoustic neuroma):

Location: cerebellopontine angle (CN VIII)
Symptoms: progressive sensorineural hearing loss, tinnitus, vertigo
Histology: Antoni A (compact spindle cells in palisading pattern) + Antoni B (loose myxoid areas) + Verocay bodies (nuclear palisading around acellular zones)
Cells of origin: Schwann cells of the vestibular branch of CN VIII
Associated with NF2 (bilateral acoustic neuromas = NF2 diagnostic)

Q59. A patient with Cryptococcus neoformans meningitis is treated with Amphotericin B + Flucytosine (5-FC). Why use combination therapy?

A) Reduce cost
B) Cover additional organisms
C) Prevent development of antifungal resistance ✓
D) Reduce dosing frequency

Answer: Prevent resistance (and synergistic effect) The combination of Amphotericin B + Flucytosine (5-FC) for cryptococcal meningitis is the induction regimen (WHO/IDSA guidelines). The rationale:

Synergy: Amphotericin B damages the fungal cell membrane → increases intracellular penetration of 5-FC → 5-FC is converted to 5-fluorouracil → inhibits DNA/RNA synthesis
Prevent resistance: Using 5-FC alone rapidly selects resistant mutants (mutations in cytosine deaminase/permease). Combination prevents this.
Faster CSF sterilization compared to monotherapy

After 2 weeks induction → consolidation with fluconazole → maintenance fluconazole.

Q60. A patient with painful genital ulcers is diagnosed with chancroid. What is the diagnostic test?

A) Dark-field microscopy (syphilis)
B) Tzanck smear (HSV)
C) Nucleic acid amplification test (NAAT)/Nucleic acid probe for Haemophilus ducreyi ✓
D) VDRL

Answer: Nucleic acid probe/NAAT for Haemophilus ducreyi Chancroid is caused by Haemophilus ducreyi - a gram-negative coccobacillus. It presents with: painful genital ulcers (soft, undermined edges), unilateral tender inguinal lymphadenopathy (bubo). Diagnosis:

Gold standard: Culture on selective media (difficult, <80% sensitivity)
NAAT/Nucleic acid probe: PCR-based, high sensitivity and specificity, detects H. ducreyi DNA
Gram stain: "school of fish" pattern (gram-negative coccobacilli)
Clinical diagnosis often made by exclusion (HSV-negative, syphilis-negative + compatible presentation)

Treatment: Azithromycin 1g single dose or ceftriaxone 250mg IM.

Summary Table

Q	Key Answer	Core Concept
1	Intestinal obstruction	Taenia adult worm, mechanical blockage
2	Parathyroid adenoma (benign)	Primary hyperparathyroidism triad
3	Mononuclear cell infiltrate at SCJ	Chronic cervicitis histology
4	Mature cystic teratoma	Skin/hair/teeth = dermoid cyst
5	Acid-fast slit-skin smear	Leprosy diagnosis
6	Hypocalcemia	Steroid-induced calcium loss
7	PRNP gene mutation	Prion disease mechanism
8	Case-control	Backward/retrospective study design
9	Jaundice NOT typical	Uncomplicated acute cholecystitis
10	MMR (live vaccine)	Contraindicated in immunocompromised
11	Gastric acid	GERD-related reflux esophagitis
12	Nystagmus	Phenytoin toxicity
13	WBC cast	Acute pyelonephritis
14	Mask visceral pain	Opioid in acute abdomen
15	Proteus sp.	Urease+, swarming, alkaline urine
16	Atherosclerosis	Diabetes + dyslipidemia = MCA stroke
17	Circulatory disease	Leading cause of death in Malaysia
18	Choriocarcinoma	Post-menopausal bleeding, no mass
19	Thrombotic microangiopathy	Drug-induced nephrotoxicity
20	Previous C-section	Oxytocin + uterine scar = rupture risk
21	Collecting duct	Spironolactone MOA (aldosterone antagonist)
22	Subepithelial immune deposits	Membranous nephropathy ("spikes")
23	DEC (not praziquantel)	Filariasis treatment
24	Trastuzumab (not tamoxifen)	HER2+ breast cancer
25	Testicular torsion	Adolescent acute scrotal pain
26	Ability to cause clinical disease	Definition of virulence
27	Candida albicans	Cottage-cheese discharge
28	Wound swab	Tetanus investigation
29	Primary adrenal insufficiency	High ACTH + pigmentation + electrolyte imbalance
30	Block estrogen receptors	Clomiphene MOA
31	Scalloped colloid	Graves' disease histology
32	p17 protein	Early HIV marker
33	Low D2 affinity	Clozapine vs. tardive dyskinesia
34	Infects epithelial surface layer	HPV wart mechanism
35	Anthropometry	Direct nutritional assessment
36	E. histolytica (dysentery)	Giardia = pear shape but watery diarrhea
37	Decreased GFR	Obstructive uropathy physiology
38	Complement activation	Hepatitis E jaundice mechanism
39	Columnar + goblet cells (hamartoma)	Peutz-Jeghers polyp histology
40	Adenocarcinoma (linitis plastica)	Diffuse gastric carcinoma
41	Retrograde axonal transport	Rabies CNS spread
42	Metacercaria (not cercaria)	Fasciola infective stage
43	Not significant (p > 0.05)	p-value 0.4 interpretation
44	Vasogenic edema	BBB breakdown, extracellular edema
45	Metronidazole + luminal agent	Amoeba cyst eradication
46	Death irrespective of pregnancy duration	Why MMR = health system indicator
47	Clear cell renal carcinoma	Clear cytoplasm, hematuria, renal mass
48	Agent, Host, Environment	Epidemiological triad
49	Hemolytic anemia (G6PD)	Sulfonamide side effect
50	Urine microscopy	Schistosoma haematobium diagnosis
51	Autoimmune demyelination (MS)	Oligoclonal bands + demyelination
52	Acute adrenal insufficiency	Steroid withdrawal HPA suppression
53	Growth hormone	Turner syndrome treatment
54	Adhesins	Campylobacter virulence
55	Lipodystrophy	Repeated insulin injection site
56	Benzodiazepine - Cl- influx	GABA-A receptor, anxiolytic
57	Ovary (FSH/LH) - early loss	Hypopituitarism sequence
58	Schwann cells	Vestibular schwannoma histology
59	Prevent resistance + synergy	Ampho B + 5-FC for Cryptococcus
60	NAAT/nucleic acid probe	Chancroid (H. ducreyi) diagnosis

Notes on discrepancies in listed answers:

Q23: Praziquantel is for trematodes/cestodes; DEC is correct for filariasis
Q24: Tamoxifen is for ER+ cancer; Trastuzumab is correct for HER2+
Q42: Cercaria is listed but Metacercaria is the true infective stage of Fasciola

1. A 63-year-old man is admitted in the hospital with complaints of persistent abdominal pain, nausea, weight loss, and early satiety. Physical examination reveals enlarged supraclavicular lymph nodes and a palpable upper abdominal mass. The patient undergoes gastrectomy which reveals a diffusely infiltrative malignant neoplasm involving the stomach. Which of the following histologic subtype of gastric neoplasms is most likely to be present in this patient? Neuroendocrine carcinoma Squamous cell carcinoma Adenocarcinoma Gastrointestinal stromal tumour 2. Epidemiologists have identified the epidemiologic triad of disease as a traditional model of infectious disease causation. Which of the following combinations indicates the components of the epidemiological triad? kengue Primary prevention, secondary prevention, tertiary prevention. Source, mode of transmission, susceptible host. Time, place, person Agent, host, environment. 3. A55-year-old woman, who lives in a squatter area, presents to the hospital with fatigue and yello wish discoloration of her sclera. Her investigations show high bilirubin levels and positive Hepa itis E immunoglobulin M. Whict of the following pathogenic mechanisms is involved in hepatocellular destruction in this case? Cell lysis by viral replication Hyperactivity of cytotoxic T cells Excessive release of antibodies Complement system activation

Here are the three questions answered fully:

Q1. A 63-year-old man with persistent abdominal pain, nausea, weight loss, early satiety, enlarged supraclavicular lymph nodes, palpable upper abdominal mass, and diffusely infiltrative malignant neoplasm on gastrectomy. What is the histologic subtype?

Neuroendocrine carcinoma
Squamous cell carcinoma
Adenocarcinoma ✓
Gastrointestinal stromal tumour

Answer: Adenocarcinoma

Explanation:

Key clues in this question:

Clinical Feature	Significance
Diffusely infiltrative malignant neoplasm	Points to diffuse-type adenocarcinoma (linitis plastica)
Enlarged supraclavicular lymph node	Virchow's node - classic sign of upper GI (gastric) malignancy spreading via thoracic duct
Early satiety + weight loss	Stomach losing distensibility due to diffuse wall infiltration
Palpable upper abdominal mass	Advanced gastric carcinoma

Gastric adenocarcinoma is the most common malignant tumor of the stomach, accounting for ~90-95% of all gastric cancers.

Using the Lauren classification, adenocarcinoma is divided into two main types:

1. Intestinal type:

Forms glands (tubular/papillary architecture)
Discrete expanding mass
Associated with H. pylori, chronic atrophic gastritis, intestinal metaplasia
More common in elderly men, high-risk areas (East Asia, Eastern Europe)
Better prognosis

2. Diffuse type:

NO gland formation
Diffuse infiltration of the stomach wall by signet ring cells (intracellular mucin pushes nucleus to periphery)
Causes linitis plastica ("leather bottle stomach") - rigid, thickened stomach wall
Associated with CDH1 (E-cadherin) gene mutation
More common in younger patients and women
Worse prognosis

This patient's "diffusely infiltrative" pattern = diffuse-type adenocarcinoma.

Why not the others?

Neuroendocrine carcinoma: rare, arises from enterochromaffin cells, usually small/discrete, associated with carcinoid syndrome
Squamous cell carcinoma: extremely rare in stomach (stomach is lined by glandular epithelium, not squamous)
GIST (Gastrointestinal Stromal Tumour): arises from interstitial cells of Cajal, forms a discrete submucosal mass, spindle or epithelioid cells on histology, positive for c-KIT (CD117) - does NOT diffusely infiltrate the wall like linitis plastica

Virchow's node (left supraclavicular lymph node enlargement) occurs because gastric cancer cells travel via the thoracic duct to the left subclavian vein junction. Its presence indicates M1 (distant metastatic) disease.

Q2. The epidemiological triad is the traditional model of infectious disease causation. Which combination indicates its components?

Primary prevention, secondary prevention, tertiary prevention
Source, mode of transmission, susceptible host
Time, place, person
Agent, host, environment ✓

Answer: Agent, Host, Environment

Explanation:

The Epidemiological Triad (Triangle) is the oldest and most fundamental model of infectious disease causation. It proposes that disease results from the dynamic interaction of three components:

        AGENT
       /     \
      /       \
   HOST ---ENVIRONMENT

1. AGENT

The causative organism or factor
Biological agents: bacteria, viruses, fungi, parasites, prions
Chemical agents: toxins, pollutants
Physical agents: radiation, trauma
Properties: infectivity, pathogenicity, virulence, antigenicity, toxigenicity

2. HOST

The susceptible individual
Factors: age, sex, genetics, immune status, nutritional status, behavior, occupation
Determines susceptibility and response to infection

3. ENVIRONMENT

External conditions that influence exposure and transmission
Physical: climate, temperature, geography, sanitation
Biological: vectors, reservoirs, flora
Social: overcrowding, poverty, healthcare access
The "squatter area" in Q3 below is an environmental risk factor for Hepatitis E

Disease occurs when the balance between these three is disrupted - e.g., a highly virulent agent meets an immunocompromised host in a contaminated environment.

Why not the other options?

Primary/secondary/tertiary prevention = levels of prevention (not the triad)
Source, mode of transmission, susceptible host = the chain of infection model (different framework)
Time, place, person = descriptive epidemiology variables used to characterize disease distribution (epidemiological descriptors, not the triad)

Q3. A 55-year-old woman from a squatter area presents with fatigue and yellowish scleral discoloration. High bilirubin + positive Hepatitis E IgM. What pathogenic mechanism causes hepatocellular destruction?

Cell lysis by viral replication
Hyperactivity of cytotoxic T cells
Excessive release of antibodies
Complement system activation ✓

Answer: Complement System Activation

Explanation:

Hepatitis E virus (HEV):

RNA virus, family Hepeviridae, genus Hepevirus
Transmission: fecal-oral route (contaminated water - explains squatter area setting)
Incubation: 2-8 weeks
Positive IgM anti-HEV = acute/recent infection
Self-limiting in most; fulminant in pregnant women (3rd trimester, 20-25% mortality)

How HEV destroys hepatocytes:

HEV hepatocellular injury is primarily immune-mediated, not direct viral cytolysis. The mechanism involves:

HEV infects hepatocytes → viral antigens are expressed on hepatocyte surface
Innate immune response activates complement system
Complement activation (classical pathway via antibody-antigen complexes, or lectin pathway) → membrane attack complex (MAC, C5b-9) formation on hepatocyte membranes → cell lysis
Cytokine-mediated inflammation amplifies hepatocellular damage
Elevated bilirubin (from hepatocyte destruction) → jaundice (scleral icterus)

Why not the other options?

Option	Why Incorrect
Cell lysis by viral replication	HEV is NOT directly cytopathic - it does not kill cells by replication alone
Hyperactivity of cytotoxic T cells	More characteristic of Hepatitis B/C (CTL-mediated destruction is the dominant mechanism in HBV/HCV)
Excessive release of antibodies	Antibodies alone do not lyse cells without complement; antibody-mediated liver destruction is not the primary HEV mechanism
Complement activation	Correct - immune complex formation triggers complement cascade → hepatocyte lysis → jaundice

Clinical correlation:

The squatter area setting = poor sanitation/contaminated water supply = risk for enteric hepatitis (HEV, HAV)
IgM positivity confirms acute HEV infection (IgM appears first, peaks at 4 weeks, fades by 3-4 months)
IgG anti-HEV = past infection/immunity
High bilirubin from hepatocyte necrosis → conjugated hyperbilirubinemia → scleral jaundice

Quick Summary

Q	Answer	Core Reason
1	Adenocarcinoma	Diffuse infiltrative pattern = linitis plastica; Virchow's node = gastric malignancy
2	Agent, Host, Environment	Classic epidemiological triad components
3	Complement system activation	HEV = immune-mediated (not direct cytopathic) hepatocyte destruction

A 45-year-old woman with a non-functioning pituitary adenoma develops symptoms of 24. Which of the fol owing target Srgans is most likely the first to be affected in the course of her symptoms? hypopituitarism ._ Adrenal cortex Breast Ovary Thyroid 5. A 40-year-old man, who is on urinary catheterization, develops urinary tract infection. His urine is found to be alkaline. Urine culture on MacConkey agar reveals yellowish-coloured swarming colonies. The colonies contain Gram-negative bacilli which are positive for urease test. Which of the following organisms is most likely the causative agent of the above infection? Proteus mirabilis Pseudomonas aeruginosa Escherichia coli Enterobacter cloacae 6. A28-year-old man visits the outpatient clinic with complaints of terminal haematuria. The attending doctor suspects Schistosoma haematobium infection. Whict of the following investigations is most likely the simplest to diagnose the above infection? Serology Urine examination Cystoscopy Blood culture 7. A 77-year-old woman is admitted to the hospital with a 6-8-week history of rapid deterioration in her memory, unsteady gait and jerking right arm. Based on the neurological assessment, MRI scan, EEG and CSF findings, a diagnosis of prion disease is made. Which of the following mechanisms is most commonly involved in the pathogenesis of the above disease? Mutation of normal cellular protein gene Normal cellular protein changes by autoimmunity Prion sc protein changes normal cellular protein Spontaneous change in normal cellular protein 8. A 56-year-old schizophrenia patient was on haloperidol treatment for the past 6 months. The psychiatrist decides to change her medication to clozapine that causes less extrapyramidal side-effects compared to haloperidol. Which of the following pharmacological actions of clozapine best explains the rationale to choose it? Blocks dopamine release Activates GABA receptors Has a low affinity for dopamine D2 receptors Has greater antagonism at muscarinic receptors 9. A42-year-old man diagnosed with cirrhosis of liver is prescribed with spironolactone for ascite s. Whict of the following parts of nephron is the site of action of the prescribed drug? Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct 10. A 65-year-old man with ischaemic stroke develops cerebral oedema after 1 week. CT brain shows features of vasogenic type cerebral oedema. Which of the following mechanisms most likely contributes to the current stage of cerebral oedema? Increased CSF production Malfunctioning blood brain barrier Low sodium levels Increased blood supply 11. A 53-year-old woman presents to the clinic with a fractured wrist. Recently she was diagnosed with Crohn's Disease and is prescribed high dose prednisone for frequent relapses. The physician suspects it to be a case of drug-induced hypocalcaemia. Which of the following reasons best explain the adverse effect of the above-mentioned drug? Increased calcium chelation Inhibition of calcium absorption Net negative calcium balance Interference with bone mineralization 12. Agro up of students discuss on the drugs that stimulate uterine contraction, especially oxytc in. They notice that this drug is contraindicated in certain pregnant women. Whic of the following obstetric histories in the patient is most likely the reason to avoid this c ug? History of early rupture of membranes History of gestational diabetes History of caesarean section History of eclampsia 13. A 40-year-old woman with systemic lupus erythematous has multiple episodes of relapse which requires chronic systemic therapy of corticosteroids. Which of the following side effects most likely occurs with abrupt withdrawal of the above-mentioned drug? Rebound hypertension Hyperglycemia Acute adrenal insufficiency Psychological dependence 14. A 25-year-old woman visits the outpatient gynaecological clinic with complaints of vulvar itching with thick, white curd-like cottage cheese vaginal discharge. Which of the following organisms most likely causes the above infection? Neisseria gonorrhoeae Trichomonas vaginalis L badw A vainaris 7/t.s Chlamydia trachomatis Candida albicans 6 4.5 15. A 34-year-old lady presents with recurrent episodes of paraesthesia of the hand which resolves after a few days. A few months later, she presents with bilateral leg weakness with visual disturbance. Brain MRI shows changes consistent with CNS demyelination. CSF investigation reveals presence of oligoclonal band. Which of the following mechanisms most likely explains the pathogenesis of demyelination of this patient? Hypoxic ischaemic demyelination MV Autoimmune demyelination Viral related demyelination Acquired metabolic demyelination 16. A 38-year-old man visits the outpatient clinic with complaints of fever, jaundice and right hypochondrial pain. Blood examination reveals eosinophilia (80%). Stool examination reveals Fasciola spp. egg. Which of the following mode of transmissions most likely would have resulted in the above infection? Vector borne mechanical transmission of egg. Skin penetration by cercaria. Inhalation of organism egg. Ingestion of encysted metacercaria on green vegetables. 17. A 56-year-old man complains of puffiness around his eyes since the past two weeks. A 24-hour urine collection yields 4.2 gm of protein. Renal biopsy shows uniform, diffuse thickening of glomerular capillary wall with irregular spikes protruding from glomerular basement membrane. Which part of the glomeruli is most likely to show immune complex deposition resulting in the glomerular disorder in this patient? 3.5 wire Subendothelial aspect of the basement membrane Subepithelial aspect of the basement membrane Mesangial and para-mesangial region Central lamina densa region of the basement membrane 18. According to National Health and Morbidity Survey 2015, non-communicable diseases accounted for 74% of death in Malaysia. Which of the following conditions is most likely to contribute to the highestnumber of deaths in Malaysian hospitals as per the above statement? Diseases of the respiratory systemx Neoplasms Diseases of the circulatory system Diseases of the digestive systey 19. A study is conducted to investigate the association between pervasive development disorders (e.g., autism and Asperger's syndrome) and Measles-Mumps-Rubella (MMR) vaccination. The participants are 1,294 children with such disorders and 4,469 children without such disorders. Which of the following study designs is most appropriate to fit this research? Case-control Cohort Observational Analytical 7 20. A 42-year-old businessman presents to the clinic with difficulty in sleeping. After assessment, he is diagnosed with anxiety and prescribed with benzodiazepines. Which of the following mechanism of actions is most likely produced by the prescribed drug? Increases the inhibitory effect of GABA on neuronal excitability Increases the duration of GABA-mediated chloride ion channel opening Agonises brain serotonin receptors partially Activates melatonin receptors in the suprachiasmatic nuclei x 21. A 3-year-old girl presents to the pediatric clinic with short stature for her age and appears to have loose skin on her neck. Cytogenetic testing reveals an XO karyotype. Which of the following drugs is most likely to be prescribed for her to achieve a higher adult height? Adrenocorticotropin (ACTH) Growth hormone-releasing hormone (GHRH) Corticotropin-releasing hormone (CRH) Somatropin 22. A 29-year-old man presents to the Outpatient Clinic with the complaints of painful genital ulcers of one week duration. A diagnosis of chancroid is made based on microbiological investigations. Which of the following diagnostic tests is gold standard to confirm the causative organism of this disease? Light microscopy Nucleic acid probe Tissue biopsy Lesion culture de nu 23. The maternal mortality rute can indicate/the level of health system development of a particular country. Which of the following statements best describes the above indicator? It is a measure of maternal death irrespective of the duration of pregnancy. It is a measure of mothers' life expectancy. It is a measure of women death rate within 42 days of pregnancy termination. It is a measure of women death rate while pregnant. 24. A 9-year-old boy presents with a new onset of oliguria and cola-coloured smoky urine after recovering from an episode of sore throat. Physical examination shows the presence of periorbital oedema and hypertension. Laboratory investigations show elevated serum urea and creatinine, mild proteinuria and hypocomplementemia. Which of the following findings is most likely to be demonstrated in microscopic urinalysis of this patient? Granular casts WBC casts Fatty casts RBC casts 25. A 20-year-old woman presents to the clinic with reddish cauliflower-like lesions on her genitalia. A clinical diagnosis of genital wart due to Human Papilloma Virus (HPV) is made. Which of the following statements is the most suitable to describe the pathogenesis at this stage of infection in the patient? Wart development depends on the viral strain. Cellular proliferation is stimulated by HPV infection. Viral protein inhibits the function of tumour suppressor protein. HPV infects the surface cell layer of epithelial tissue. 26. A man visits the clinic for routine medical check-up. Stool test shows presence of Entamoeba histolytica cysts. The physician prescribes a drug to eradicate the cyst from his gastrointestinal tract. Which of the following drugs is most likely prescribed to him? Metronidazole +s- Diloxanide furoate Chloroquine 3s Dihydroemetine 27. A 65-year-old woman presents to the Emergency Department with weakness of right arm, right leg and slurring of speech. She is a known diabetic and has dyslipidaemia. Computed Tomography (CT) scan of brain reveals an infarct in the left middle cerebral artery territory. Which of the following conditions is the most likely cause of cerebral infarction in this patient? Atherosclerosis Cerebral vasculitis Vascular spasm Embolism from cardiac mural thrombi fca l 28. A 42-year-old woman presents with fatigue and chronic diarrhoea over the past 9 months. On examination she has increased pigmentation in her oral mucosa and hypotension. Laboratory tests show hyponatremia and hyperkalemia. Her serum cortisol level is low and ACTH level is high. She is diagnosed with adrenal insufficiency. Which of the following conditions is the most likely cause of adrenal insufficiency in this patient? Addison disease Waterhouse Friderichsen syndrome Pituitary failure Hypothalamic failure 29. A 34-year-old woman presents to the clinic with fever, fatigue, and a feeling of fullness in the anterior neck for the past one week. Three weeks ago, she had upper respiratory tract infection. Palpation of her diffusely enlarged thyroid gland elicits pain. Laboratory investigations reveal high serum T3 and T4 levels and low serum TSH levels. Which of the following pathologic changes is most likely to be present in the thyroid gland of the patient? Scalloped margin of colloids Hurthle cell metaplasia Formation of germinal centres Granulomatous inflammation 30. A 45-year-old man presents with polyuria and nocturia. He has history of urological surgery. Imaging studies reveal narrowing of right ureter due to scarring and right sided hydronephrosis. He is diagnosed with obstructive uropathy. Which of the following pathological changes in the kidney is the most likely cause of polyuria in this patient? Reduced concentrating ability of tubules Chronic interstitial inflammation Venous stasis Reduced glomerular filtration 31. A 35-year-old man presents to the hospital with fever, lockjaw, and urine incontinence of two- day duration. History reveals that he had stepped on a rusty nail a week ago. On examination, a deep wound is observed on the heel of his right foot. The attending doctor suspects that he is suffering from tetanus. Which of the following specimens should be obtained from the patient for lab investigations to aid in the diagnosis? Wound swab Throat swab Blood specimen Urine specimen 32. A 25-year-old woman who presents with a right ovarian mass undergoes ovariectomy. The resected specimen shows a cyst of size 8 cm containing keratinous material. Cyst wall shows a protuberance with skin, hair, and teeth. Which of the following types of ovarian cysts is most likely to be found in this patient? Mature cystic teratoma Endometriotic cyst Follicular cyst Mucinous cystadenoma 33. A 53-year-old man comes to the clinic due to gradual hearing loss and tinnitus which has occurred over the past few years. Clinical examination reveals sensorineural hearing loss. Magnetic resonance imaging (MRI) shows a well circumscribed neoplasm at the cerebellopontine angle in the posterior cranial fossa. Histologic section of the lesion shows Antoni-A area, Antoni-B area and Verocay bodies. Which of the following cells have given rise to the above tumour? Ependymal cell Oligodendrocyte Astrocyte Schwann cell 34. A 22-year-old man presents to the clinic with complaints of abdominal pain, diarrhoea and perianal itching and irritation. Stool examination reveals egg of Taenia solium. Which of the following complications is most common to occur due to the above parasitic infestation? Intestinal obstruction Rectal prolapse Cysticercosis Microcytic hypochromic anaemia

Here are all 34 questions answered fully with explanations:

Q4. A 45-year-old woman with a non-functioning pituitary adenoma develops hypopituitarism. Which target organ is FIRST affected?

Adrenal cortex
Breast
Ovary ✓
Thyroid

Answer: Ovary (Gonadal axis - FSH/LH)

Explanation:

In hypopituitarism caused by a pituitary adenoma (compression of normal pituitary tissue), anterior pituitary hormones are lost in a predictable sequence from most sensitive to least sensitive:

Order	Hormone Lost	Target Organ Affected	Clinical Feature
1st	GH (growth hormone)	Liver/muscle/bone	Growth failure, fatigue
2nd	FSH/LH (gonadotropins)	Ovary/Testes	Amenorrhea, infertility, loss of libido
3rd	TSH	Thyroid	Hypothyroidism symptoms
4th	ACTH	Adrenal cortex	Adrenal insufficiency (most dangerous)
Variable	Prolactin	Breast	May increase (stalk compression removes dopamine inhibition)

Key concept: GH-secreting cells are most numerous and most sensitive to compression. Gonadotroph cells (FSH/LH) are next. The mnemonic is "Go Fly To Acapulco" → GH, FSH/LH, TSH, ACTH.

Among the listed options, Ovary (FSH/LH axis) is affected earliest. Adrenal cortex (ACTH) is the LAST to fail - but is the most life-threatening when it does.

Why not Breast? Prolactin may actually increase in pituitary stalk compression because dopamine (the inhibitor of prolactin) cannot reach the pituitary, causing hyperprolactinemia (galactorrhea, amenorrhea).

Q5. A catheterized patient with alkaline urine, swarming yellowish colonies on MacConkey, Gram-negative bacilli, urease-positive. What is the organism?

Proteus mirabilis ✓
Pseudomonas aeruginosa
Escherichia coli
Enterobacter cloacae

Answer: Proteus mirabilis

Explanation:

Each clue points specifically to Proteus mirabilis:

Feature	Significance
Alkaline urine	Urease splits urea → NH3 + CO2 → alkaline urine (pH >7)
Swarming colonies	Proteus has flagella enabling characteristic concentric ring swarming on agar
Yellowish colonies on MacConkey	Non-lactose fermenter (pale/colorless, may appear yellow)
Gram-negative bacilli	Enterobacteriaceae family
Urease positive	Strongest urease producer among common uropathogens
Urinary catheter	Proteus is a common healthcare-associated/catheter UTI pathogen

Clinical importance of Proteus UTI:

Alkaline urine from urease activity → struvite (triple phosphate) stone formation (magnesium ammonium phosphate)
Stones can form staghorn calculi filling the entire renal pelvis
Treatment: fluoroquinolones or trimethoprim-sulfamethoxazole

Why not others?

E. coli: lactose fermenter (pink on MacConkey), does NOT swarm, weakly urease positive
Pseudomonas: non-fermenter, oxidase positive, blue-green pigment (pyocyanin), grape-like odor - does NOT swarm
Enterobacter: lactose fermenter (pink colonies), does NOT swarm, urease variable

Q6. A 28-year-old man with terminal hematuria - suspected Schistosoma haematobium. Simplest investigation?

Serology
Urine examination ✓
Cystoscopy
Blood culture

Answer: Urine examination

Explanation:

Schistosoma haematobium uniquely targets the vesical (urinary bladder) venous plexus, making urine the ideal specimen.

Why urine examination is simplest and most direct:

S. haematobium adult worms reside in the vesical plexus → lay eggs → eggs penetrate bladder wall → excreted in urine
Microscopy of urine (especially midday urine, 10am-2pm, when egg excretion peaks) shows characteristic terminal-spined eggs
Simple, non-invasive, cheap, rapid
Can also detect hematuria (macro or micro) in the same sample

Egg characteristic:

Large, oval egg with a terminal (end) spine - diagnostic of S. haematobium
Contrast: S. mansoni has a lateral spine, S. japonicum has a rudimentary lateral spine

Clinical features:

Terminal hematuria (blood at the end of urination - due to bladder wall involvement)
Dysuria, frequency
Chronic infection → bladder fibrosis, calcification ("fetal head" calcification on X-ray)
Increased risk of bladder squamous cell carcinoma

Why not others?

Serology: useful for epidemiology/diagnosis in non-endemic areas but less specific and cannot assess current worm load
Cystoscopy: invasive, expensive, shows bladder lesions but not first-line
Blood culture: irrelevant - Schistosoma is not bacteremic

Treatment: Praziquantel (drug of choice for ALL Schistosoma species)

Q7. A 77-year-old woman with rapid memory deterioration, unsteady gait, jerking arm. Diagnosed with prion disease. What is the most common pathogenic mechanism?

Mutation of normal cellular protein gene
Normal cellular protein changes by autoimmunity
Prion Sc protein changes normal cellular protein ✓
Spontaneous change in normal cellular protein

Answer: PrPSc (abnormal prion protein) converts normal cellular protein (PrPC → PrPSc)

Explanation:

Prion diseases (Transmissible Spongiform Encephalopathies - TSEs) include:

Creutzfeldt-Jakob Disease (CJD) - classic
Variant CJD (vCJD - from BSE/"mad cow")
Gerstmann-Straussler-Scheinker (GSS)
Fatal Familial Insomnia (FFI)
Kuru

Pathogenic mechanism - the "protein-only" hypothesis:

Normal PrPC (cellular prion protein)
        ↓  [PrPSc acts as a template/seed]
Misfolding to PrPSc (Scrapie isoform)
        ↓
PrPSc is protease-resistant, accumulates
        ↓
Neuronal vacuolation → spongiform encephalopathy

PrPC vs PrPSc:

Property	PrPC (normal)	PrPSc (abnormal)
Structure	Alpha-helices (soluble)	Beta-sheets (insoluble)
Protease sensitivity	Sensitive (degraded)	Resistant
Infectivity	None	Infectious
Location	Cell surface	Accumulates in neurons

Three forms of prion disease:

Sporadic (~85%): Spontaneous PrPC → PrPSc conversion (spontaneous misfolding)
Familial (~15%): Mutation in PRNP gene making PrPC more prone to misfolding
Acquired (<1%): Transmission of PrPSc (surgical instruments, corneal transplant, growth hormone, vCJD from beef)

The most COMMON mechanism overall is: PrPSc converting PrPC (sporadic CJD - spontaneous misfolding propagated by PrPSc template). The question lists this as "Prion Sc protein changes normal cellular protein" - this is the correct answer.

Clinical features of CJD:

Rapidly progressive dementia (weeks-months)
Myoclonus (jerking - as in this patient)
Cerebellar ataxia (unsteady gait)
EEG: periodic sharp wave complexes
MRI: DWI hyperintensity in basal ganglia/cortex ("cortical ribboning")
CSF: 14-3-3 protein (marker of neuronal death), RT-QuIC

Q8. A 56-year-old schizophrenic on haloperidol develops tardive dyskinesia. Switched to clozapine. Which pharmacological action explains the choice?

Blocks dopamine release
Activates GABA receptors
Has a low affinity for dopamine D2 receptors ✓
Has greater antagonism at muscarinic receptors

Answer: Low affinity for D2 receptors

Explanation:

Tardive Dyskinesia (TD) pathophysiology:

Haloperidol (typical antipsychotic) chronically blocks D2 receptors in the nigrostriatal pathway
Prolonged D2 blockade → D2 receptor upregulation and supersensitivity
Supersensitive D2 receptors in striatum → involuntary, repetitive movements (lip smacking, tongue protrusion, choreiform movements)

Why Clozapine works:

Property	Haloperidol	Clozapine
D2 receptor affinity	High	Low
Striatal D2 occupancy	~80%	~20-40%
Receptor binding kinetics	Tight ("stay")	Loose/rapid dissociation ("hit and run")
EPS/TD risk	High	Lowest of all antipsychotics
Main receptor targets	D2	D4, 5-HT2A, H1, M1, alpha-1

Clozapine's low D2 affinity means it does NOT cause the striatal D2 supersensitivity that drives TD. Its antipsychotic effect comes mainly from D4 and 5-HT2A antagonism plus limbic (not striatal) D2 blockade.

Clozapine special side effects:

Agranulocytosis (1-2%) - requires regular CBC monitoring (weekly for 6 months)
Seizures (dose-dependent)
Metabolic syndrome, weight gain
Hypersalivation (sialorrhea)
Myocarditis

Clozapine indications:

Treatment-resistant schizophrenia (failed 2+ antipsychotics)
Schizophrenia with tardive dyskinesia
Suicidality in schizophrenia

Q9. A 42-year-old man with liver cirrhosis and ascites is given spironolactone. Where does it act in the nephron?

Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct ✓

Answer: Collecting duct (cortical collecting duct - principal cells)

Explanation:

Spironolactone is a competitive aldosterone antagonist (potassium-sparing diuretic).

Site of action:

Aldosterone normally acts on:
  → Cortical Collecting Duct (CCD) principal cells
  → Binds mineralocorticoid receptor (MR)
  → Upregulates ENaC (apical Na+ channel) & Na+/K+ ATPase (basolateral)
  → Na+ reabsorbed, K+ and H+ secreted

Spironolactone competitively binds the mineralocorticoid receptor in principal cells of the cortical collecting duct → blocks aldosterone's effect → decreased Na+ reabsorption → decreased K+ excretion → natriuresis + K+ retention

Why useful in cirrhosis/ascites:

Cirrhosis → portal hypertension → reduced effective circulating volume → hyperaldosteronism (secondary)
Elevated aldosterone → Na+ retention → fluid retention → ascites
Spironolactone blocks aldosterone → reduces Na+ retention → reduces ascites

Nephron segment comparison of diuretics:

Drug	Site	Mechanism
Acetazolamide	PCT	Carbonic anhydrase inhibitor
Furosemide	Thick ascending LOH	NKCC2 blocker
Thiazides	Early DCT	NCC blocker
Spironolactone/Amiloride	CCD	Aldosterone antagonist / ENaC blocker

Note: Spironolactone acts primarily on the collecting duct, not DCT, though the late DCT also has some aldosterone-sensitive segments.

Q10. A 65-year-old with ischemic stroke develops vasogenic cerebral edema after 1 week. What is the mechanism?

Increased CSF production
Malfunctioning blood-brain barrier ✓
Low sodium levels
Increased blood supply

Answer: Malfunctioning (disrupted) blood-brain barrier

Explanation:

Types of cerebral edema:

Type	Mechanism	Cause	Location
Vasogenic	BBB breakdown → plasma fluid leaks into extracellular space	Tumors, abscess, trauma, post-ischemic	White matter
Cytotoxic	Cell membrane pump failure → intracellular swelling	Acute ischemia (early), hypoxia	Gray + white matter
Interstitial	CSF crosses ependyma	Hydrocephalus	Periventricular
Osmotic	Serum hypo-osmolality	Hyponatremia	Diffuse

In this patient (post-ischemic vasogenic edema at 1 week):

Sequence of events:

Acute ischemia → cytotoxic edema (first few hours - Na+/K+ ATPase fails)
Reperfusion + inflammation → BBB disruption (tight junctions breakdown)
24-72h onward → vasogenic edema develops and peaks at ~3-5 days
Plasma proteins (albumin) and fluid leak from blood vessels into extracellular (interstitial) space
Increased extracellular water → brain swelling → raised ICP

Vasogenic edema features:

Predominantly white matter (more extracellular space)
Responds to dexamethasone (reduces BBB inflammation) - useful in tumor/abscess edema
CT: finger-like hypodensity projecting from lesion into white matter

Q11. A patient on high-dose prednisone for Crohn's disease gets a fractured wrist. Suspected drug-induced hypocalcemia. What is the mechanism?

Increased calcium chelation
Inhibition of calcium absorption ✓ (best answer = Net negative calcium balance)
Net negative calcium balance
Interference with bone mineralization

Answer: Net negative calcium balance (via inhibition of intestinal calcium absorption + increased renal excretion)

Explanation:

Corticosteroid-induced hypocalcemia mechanisms:

Mechanism	Detail
Reduced intestinal Ca2+ absorption	Steroids antagonize vitamin D action on enterocytes → reduced Ca2+ uptake from gut
Increased renal Ca2+ excretion	Reduced tubular reabsorption
Inhibit osteoblasts	Reduce bone formation, reduce OPG → net bone loss
Stimulate osteoclasts (RANK-L)	Increased bone resorption
Secondary hyperparathyroidism	Low Ca2+ → compensatory PTH rise → further bone resorption

The best single answer among the options:

"Inhibition of calcium absorption" - refers to the intestinal vitamin D antagonism
"Net negative calcium balance" - is actually the overall result of ALL mechanisms combined

The fractured wrist = osteoporosis from chronic steroid use (corticosteroid-induced osteoporosis). This is the most common serious long-term complication of corticosteroid therapy.

Prevention: Calcium + Vitamin D supplementation, bisphosphonates (alendronate) for patients on long-term steroids.

Q12. Oxytocin is contraindicated in which obstetric history?

History of early rupture of membranes
History of gestational diabetes
History of caesarean section ✓
History of eclampsia

Answer: History of caesarean section (previous uterine scar)

Explanation:

Oxytocin stimulates uterine contractions by binding oxytocin receptors (Gq-coupled) on myometrium → IP3 → Ca2+ release → strong uterine contractions.

Why previous C-section is a contraindication:

Previous caesarean section leaves a uterine scar (at lower segment)
Oxytocin-induced strong contractions on a scarred uterus → uterine rupture
Uterine rupture = catastrophic obstetric emergency:
- Fetal distress/death
- Maternal hemorrhage, shock, death
- Requires emergency laparotomy

Other contraindications to oxytocin:

Cephalopelvic disproportion (CPD)
Malpresentation (transverse lie, brow presentation)
Previous uterine surgery (myomectomy)
Grand multiparity (≥5 pregnancies) - uterine atony/rupture risk
Active herpes genitalis
Fetal distress before delivery

Why not others?

Gestational diabetes: not a contraindication to oxytocin
Eclampsia: actually, delivery (including induction with oxytocin) is the treatment for eclampsia - not contraindicated
Early rupture of membranes: oxytocin may actually be USED to induce labor when membranes rupture prematurely

Q13. SLE patient on chronic corticosteroids. What happens with ABRUPT withdrawal?

Rebound hypertension
Hyperglycemia
Acute adrenal insufficiency ✓
Psychological dependence

Answer: Acute adrenal insufficiency (Adrenal crisis)

Explanation:

HPA axis suppression by exogenous steroids:

Exogenous prednisolone
    ↓ (negative feedback)
Hypothalamus: ↓CRH
    ↓
Pituitary: ↓ACTH
    ↓
Adrenal cortex: ATROPHIES from disuse
    ↓ (if steroids abruptly stopped)
ADRENAL CRISIS

Features of acute adrenal insufficiency (Addisonian crisis):

Severe hypotension (not hypertension - shock from cortisol and aldosterone deficiency)
Nausea, vomiting, abdominal pain
Hyponatremia, hyperkalemia
Hypoglycemia
Fever
Altered consciousness → coma → death if untreated

Treatment: IV hydrocortisone 100mg STAT, IV fluids (normal saline), glucose

Rule of thumb for steroid tapering:

Patients on >20mg prednisone/day for >3 weeks need gradual tapering
Stress dosing needed for surgery, illness (sick day rules)
Never abruptly stop after prolonged steroid use

Q14. A 25-year-old woman with vulvar itching and thick, white curd-like cottage cheese discharge. Causative organism?

Neisseria gonorrhoeae
Trichomonas vaginalis
Chlamydia trachomatis
Candida albicans ✓

Answer: Candida albicans

Explanation:

Vaginal discharge comparison:

Organism	Discharge	pH	Other features
Candida albicans	Thick, white, curdy "cottage cheese"	<4.5 (normal/acidic)	Vulvar pruritus, erythema, burning
Trichomonas vaginalis	Frothy, yellow-green, profuse	>4.5 (alkaline)	"Strawberry cervix," fishy odor, motile protozoa
Gardnerella vaginalis (BV)	Thin, gray, homogeneous	>4.5	"Fishy" amine odor, clue cells, no itch
Neisseria gonorrhoeae	Purulent, yellow-green	-	Cervicitis, dysuria, PID
Chlamydia	Mucopurulent	-	Often asymptomatic, cervicitis

Candida albicans features:

Most common cause of vulvovaginal candidiasis
KOH wet mount: pseudohyphae and budding yeast (blastoconidia)
Culture: creamy white colonies on Sabouraud's dextrose agar
Germ tube test: positive (Candida albicans specific)
Risk factors: antibiotics, diabetes, pregnancy, OCP, immunosuppression, tight clothing

Treatment:

Topical: clotrimazole, miconazole (single dose 500mg pessary)
Oral: fluconazole 150mg single dose
Recurrent (≥4 episodes/year): fluconazole weekly for 6 months

Q15. A 34-year-old woman with episodic paraesthesia, bilateral leg weakness, visual disturbance, CNS demyelination on MRI, oligoclonal bands in CSF. Pathogenesis?

Hypoxic ischemic demyelination
Autoimmune demyelination ✓
Viral related demyelination
Acquired metabolic demyelination

Answer: Autoimmune demyelination (Multiple Sclerosis)

Explanation:

This is a classic presentation of Multiple Sclerosis (MS):

Diagnostic criteria features present:

Relapsing-remitting episodes (paraesthesia resolving after days = relapse-remission)
Dissemination in space: different areas affected (sensory → motor → visual)
Dissemination in time: episodes over months
CNS demyelination on MRI: periventricular white matter plaques (Dawson's fingers)
Oligoclonal bands in CSF: intrathecal IgG synthesis (present in >95% of MS cases)

Pathogenesis of autoimmune demyelination in MS:

Autoreactive CD4+ T cells (Th1 and Th17) are activated against myelin antigens (MBP, MOG, PLP) - molecular mimicry from prior viral infection likely triggers this
T cells cross the blood-brain barrier
Activate macrophages and microglia → myelin phagocytosis
CD8+ cytotoxic T cells directly kill oligodendrocytes
B cells + plasma cells produce anti-myelin antibodies (IgG) → complement-mediated oligodendrocyte/myelin destruction
Loss of myelin → slowed/blocked axonal conduction → neurological deficits
Partial remyelination by oligodendrocyte precursors → clinical remission (incomplete over time)

MS treatment:

Acute relapse: high-dose IV methylprednisolone
Disease modifying: interferons (IFN-β1a/1b), glatiramer, natalizumab, fingolimod, ocrelizumab

Q16. A 38-year-old man with fever, jaundice, right hypochondrial pain, eosinophilia 80%, Fasciola spp. eggs in stool. Mode of transmission?

Vector-borne mechanical transmission of egg
Skin penetration by cercaria
Inhalation of organism egg
Ingestion of encysted metacercaria on green vegetables ✓

Answer: Ingestion of encysted metacercaria on aquatic vegetation

Explanation:

Fasciola hepatica (sheep liver fluke) life cycle:

Adult fluke in bile ducts → Eggs passed in stool → 
Miracidium hatches → Infects snail (Lymnaea sp.) → 
Sporocyst → Redia → Cercaria (leaves snail) → 
Encysts on aquatic vegetation as METACERCARIA ← INFECTIVE STAGE
↓
Human ingests metacercaria (watercress, water spinach, water chestnuts)
↓
Excysts in duodenum → Juvenile fluke penetrates gut wall → Peritoneum → 
Liver capsule → Bile ducts (adult worm)

Infective stage = Metacercaria (encysted on water plants, NOT cercaria)

Key diagnostic clue: Eosinophilia 80% = hypereosinophilia - classic for tissue-invasive helminths (Fasciola, Toxocara, Trichinella). Eosinophils are directed against IgE-coated helminth larvae.

Clinical phases:

Acute (invasive): Fever, RUQ pain, hepatomegaly, eosinophilia (larvae migrating through liver)
Chronic (biliary): Biliary obstruction, jaundice, cholangitis, choledocholithiasis

Treatment: Triclabendazole (drug of choice), or nitazoxanide

Prevention: Avoid eating raw aquatic plants; proper washing/cooking

Q17. A 56-year-old man with proteinuria (4.2g/24h), diffuse GBM thickening with irregular spikes on silver stain. Where are immune complexes deposited?

Subendothelial aspect
Subepithelial aspect of the basement membrane ✓
Mesangial and para-mesangial region
Central lamina densa

Answer: Subepithelial aspect of the basement membrane

Explanation:

Classic Membranous Nephropathy (MN):

This is a textbook presentation:

Nephrotic-range proteinuria (>3.5g/24h; here 4.2g)
Diffuse, uniform GBM thickening on light microscopy (H&E/PAS)
"Spikes" on silver stain (silver stains the GBM; immune deposits are silver-negative, creating "holes/domes" between silver-positive spikes)
No hypercellularity

Immune complex location: Subepithelial (between GBM and podocytes)

Bowman's space
      ↑
  PODOCYTE (effaced foot processes)
      ↑
[IgG + C3 immune deposits] ← SUBEPITHELIAL
      ↑
GBM (thickened, with spikes projecting up between deposits)
      ↑
  ENDOTHELIAL CELL
      ↑
  Capillary lumen

"Spike and dome" pattern:

Spikes = GBM material growing up between deposits (silver-positive)
Domes = immune deposits capping the spikes (silver-negative, PAS-positive)

Immunofluorescence: Granular IgG + C3 along capillary loops (subepithelial pattern) Electron microscopy: Electron-dense subepithelial deposits

Primary MN: Anti-PLA2R antibodies (phospholipase A2 receptor on podocytes) - most common Secondary MN: Hepatitis B, SLE (WHO class V), drugs (penicillamine, gold, NSAIDs), malignancy

Deposit location - disease association:

Location	Disease
Subepithelial	Membranous nephropathy
Subendothelial	MPGN type I, Lupus nephritis (class III/IV)
Mesangial	IgA nephropathy, HSP
Linear (GBM)	Goodpasture's disease

Q18. NHMS 2015: NCDs = 74% of deaths in Malaysia. What condition contributes MOST to hospital deaths?

Diseases of the respiratory system
Neoplasms
Diseases of the circulatory system ✓
Diseases of the digestive system

Answer: Diseases of the circulatory system

Explanation:

According to the National Health & Morbidity Survey (NHMS) 2015 and Ministry of Health Malaysia data:

Leading causes of death in Malaysian hospitals:

Diseases of the circulatory system (~22-25%) - ischemic heart disease, stroke, heart failure
Neoplasms/cancers
Diseases of the respiratory system
Diseases of the digestive system

Why cardiovascular disease leads: Malaysia has a very high NCD burden driven by:

Hypertension: ~30% prevalence
Diabetes mellitus: ~17% prevalence (one of highest in Asia)
Dyslipidemia: ~47% prevalence
Obesity: rapidly rising
Sedentary lifestyle, urbanization, dietary patterns

These risk factors fuel atherosclerosis → ischemic heart disease (IHD) and stroke = top killers.

Q19. A study on 1,294 children with autism/Asperger's and 4,469 without, investigating association with MMR vaccination. What study design is this?

Case-control ✓
Cohort
Observational Analytical
Randomized controlled trial

Answer: Case-control study

Explanation:

Study design identification:

Feature	This Study
Starting point	Disease status (autism/Asperger's = cases)
Direction	Looking BACKWARD for prior exposure (MMR vaccination history)
Groups	Cases (1,294 with ASD) vs Controls (4,469 without ASD)
Outcome measure	Odds Ratio (OR)
Design	Case-control

Case-control vs Cohort:

Feature	Case-Control	Cohort
Direction	Backward (retrospective)	Forward (prospective)
Start with	Outcome (disease)	Exposure
Measure	Odds Ratio	Relative Risk
Good for	Rare diseases, quick, cheap	Incidence, causality

This specific study design mirrors the Wakefield 1998 Lancet study (later retracted) that falsely claimed MMR caused autism. The design itself (case-control) is valid; the data interpretation was fraudulent. Multiple large case-control and cohort studies since have conclusively shown NO link between MMR vaccination and autism.

Note: "Observational Analytical" is a category of study design (which includes case-control, cohort, and cross-sectional studies) - it is not a specific design.

Q20. A 42-year-old man with anxiety and insomnia is prescribed benzodiazepines. What is the mechanism?

Increases the inhibitory effect of GABA on neuronal excitability ✓
Increases the DURATION of GABA-mediated chloride ion channel opening
Agonises brain serotonin receptors partially
Activates melatonin receptors in suprachiasmatic nuclei

Answer: Increases inhibitory effect of GABA on neuronal excitability

Note: Both options 1 and 2 describe benzodiazepine MOA - but they are asking the BEST/MOST SUITABLE description.

Explanation:

GABA-A receptor and benzodiazepines:

GABA-A receptor (ligand-gated Cl- channel)
├── GABA binding site (α subunit)
├── Benzodiazepine binding site (between α and γ subunits)
├── Barbiturate binding site (β subunit)
└── Cl- channel pore

Mechanism:

Benzodiazepines bind to the allosteric benzodiazepine site on GABA-A receptor
They do NOT activate the receptor alone - they POTENTIATE GABA's effect
In the presence of GABA, benzodiazepines → increase FREQUENCY of Cl- channel opening
↑ Cl- influx → hyperpolarization → increased inhibitory tone → reduced neuronal excitability

Important distinction:

Benzodiazepines → increase FREQUENCY of Cl- channel opening
Barbiturates → increase DURATION of Cl- channel opening

Option 2 says "increases the DURATION" - this is actually describing barbiturates (e.g., phenobarbital), not benzodiazepines. So the correct answer is Option 1.

BZD pharmacological effects: Anxiolytic, sedative/hypnotic, anticonvulsant, muscle relaxant, anterograde amnesia

Why not others?

Partial serotonin agonist = buspirone (anxiolytic, not BZD)
Melatonin receptor agonist = ramelteon (for insomnia, not anxiety)

Q21. A 3-year-old girl with short stature, loose neck skin, XO karyotype (Turner syndrome). Which drug for adult height?

Adrenocorticotropin (ACTH)
Growth hormone-releasing hormone (GHRH)
Corticotropin-releasing hormone (CRH)
Somatropin ✓

Answer: Somatropin (Recombinant human Growth Hormone)

Explanation:

Turner Syndrome (45,XO):

Short stature (most consistent feature)
Webbed neck (pterygium colli), low posterior hairline
Shield chest, widely spaced nipples
Cubitus valgus (wide carrying angle)
Gonadal dysgenesis (streak ovaries) → primary amenorrhea
Coarctation of aorta, bicuspid aortic valve
Horseshoe kidney
Intelligence: normal

Treatment for short stature:

Somatropin (recombinant GH) - FDA/EMA approved specifically for Turner syndrome
Started as early as possible (2-5 years of age)
Increases final adult height by ~5-8 cm on average
Mechanism: GH → IGF-1 (liver) → stimulates bone plate growth (epiphyseal cartilage)

Why not the others?

GHRH: a hypothalamic hormone that stimulates pituitary GH release - used for diagnosis of GH deficiency, not therapeutic for Turner syndrome
ACTH: stimulates adrenal cortisol - no role in growth
CRH: hypothalamic hormone stimulating ACTH - no role in growth

Additional Turner treatment:

Estrogen replacement at ~12-13 years for pubertal induction
Progesterone added after breakthrough bleeding for uterine development
Annual cardiac surveillance
Thyroid monitoring (↑ risk of autoimmune thyroiditis)

Q22. A 29-year-old man with painful genital ulcers - chancroid confirmed. What is the gold standard diagnostic test?

Light microscopy
Nucleic acid probe
Tissue biopsy
Lesion culture ✓

Answer: Lesion culture (Gold Standard) - though NAAT is increasingly preferred

Explanation:

Chancroid caused by Haemophilus ducreyi (Gram-negative coccobacillus):

Clinical features:

Painful genital ulcer (soft chancre) with undermined, ragged, non-indurated edges
Unilateral tender inguinal lymphadenopathy (bubo) in ~50%
No systemic symptoms
Contrast with syphilis (painless, indurated - hard chancre) and herpes (painful but vesicular/grouped)

Diagnostic tests:

Test	Notes
Culture (gold standard)	Selective media (chocolate agar + vancomycin), <80% sensitivity, requires special media/conditions
NAAT/PCR	Highest sensitivity/specificity, increasingly used in reference labs
Gram stain	"School of fish" pattern but low sensitivity (<50%)
Nucleic acid probe	Detects H. ducreyi DNA - highly accurate

Gold standard = Culture on selective media (Müller-Hinton chocolate agar with IsoVitaleX and vancomycin). However, sensitivity is low (<80%) due to fastidious nature of the organism.

In clinical practice, NAAT (PCR) is now preferred where available. The question asks for gold standard - classically this is culture.

Treatment: Azithromycin 1g single dose PO OR ceftriaxone 250mg IM single dose

Q23. Maternal mortality rate indicates health system development. Which statement best describes it?

It is a measure of maternal death irrespective of the duration of pregnancy ✓
It is a measure of mothers' life expectancy
It is a measure of women death rate within 42 days of pregnancy termination
It is a measure of women death rate while pregnant

Answer: Irrespective of duration of pregnancy

Explanation:

WHO Definition of Maternal Death: "The death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of pregnancy, from any cause related to or aggravated by the pregnancy or its management but not from accidental or incidental causes."

Breaking down the definition:

"While pregnant OR within 42 days" = covers both during pregnancy and postpartum period
"Irrespective of duration" = includes ectopic pregnancy (6 weeks), first trimester abortion, full-term delivery
"Irrespective of site" = uterine, ectopic (tubal, ovarian, abdominal)
"Any cause related to or aggravated by pregnancy" = obstetric causes (hemorrhage, eclampsia, sepsis) and indirect causes (heart disease in pregnancy)
Excludes accidental/incidental causes (car accidents, etc.)

Why options 3 and 4 are incomplete:

Option 3 ("within 42 days of termination") - incomplete because it excludes deaths while still pregnant
Option 4 ("while pregnant") - incomplete because it excludes the 42-day postpartum period

MMR formula:

MMR = (Number of maternal deaths / Number of live births) × 100,000

Why MMR reflects health system quality: Maternal deaths are largely preventable with skilled antenatal care, skilled birth attendance, emergency obstetric care, and postnatal care - making MMR a sensitive indicator of healthcare system strength.

Q24. A 9-year-old boy with oliguria, cola-colored urine, periorbital edema, hypertension, elevated creatinine, mild proteinuria, hypocomplementemia - after sore throat. What is found on urine microscopy?

Granular casts
WBC casts
Fatty casts
RBC casts ✓

Answer: RBC casts (Red blood cell casts)

Explanation:

This is a textbook case of Post-Streptococcal Glomerulonephritis (PSGN):

Diagnostic triad:

Feature	This Patient
Preceding infection	Sore throat (Group A Streptococcus - S. pyogenes)
Latent period	1-3 weeks (nephritic presentation)
Nephritic syndrome	Oliguria, hematuria, hypertension, edema
Complement	Hypocomplementemia (↓C3) - classic for PSGN
Renal function	Elevated creatinine/urea

"Cola-colored/smoky urine" = gross hematuria from RBCs leaking through damaged glomerular capillaries

Urine microscopy finding: RBC casts

Formed when RBCs enter tubular lumen (from glomerular injury) + Tamm-Horsfall protein → coalesce into casts
Pathognomonic of glomerulonephritis (glomerular hematuria vs lower tract hematuria)
Also seen in IgA nephropathy, lupus nephritis, Goodpasture's

Cast associations:

Cast	Disease
RBC casts	Glomerulonephritis (PSGN, IgA, lupus, Goodpasture's)
WBC casts	Pyelonephritis, acute interstitial nephritis
Fatty casts	Nephrotic syndrome
Granular casts	Chronic kidney disease, non-specific
Hyaline casts	Dehydration, normal (high urine concentration)
Waxy casts	Advanced CKD (end-stage)

PSGN pathogenesis: Streptococcal antigens (SPEB/zymogen, GAPDH) → immune complex formation → deposits in glomeruli → complement activation (classical + alternate pathway) → neutrophil infiltration → GFR reduction → nephritic syndrome

Q25. A 20-year-old woman with reddish cauliflower-like genital lesions (genital warts/HPV). Which statement describes the pathogenesis?

Wart development depends on the viral strain
Cellular proliferation is stimulated by HPV infection
Viral protein inhibits the function of tumour suppressor protein
HPV infects the surface cell layer of epithelial tissue ✓

Answer: HPV infects the surface cell layer of epithelial tissue

Explanation:

HPV pathogenesis in genital warts:

Micro-abrasion → HPV gains access → 
Infects BASAL KERATINOCYTES (via integrins, heparan sulfate)
↓
Viral genome maintained as episome in basal cells
↓
As cells differentiate and migrate upward...
↓
Productive viral replication occurs in SURFACE/UPPER EPITHELIAL LAYERS
↓
Viral particles assembled and released from surface cells
↓
Koilocytes (pathognomonic): vacuolated cells with perinuclear halo in superficial layers
↓
E6/E7 oncoproteins → cellular proliferation → WART formation

The best answer: "HPV infects the surface cell layer" - This is how HPV is described in the context of wart formation (active replication/particle production at surface).

Why not others?

"Depends on viral strain" - partially true (HPV 6/11 cause warts, HPV 16/18 cause cancer) but not the description of pathogenesis
"Cellular proliferation stimulated" - true but mechanism of warts, not specifically about infection process
"Inhibits tumour suppressor protein" - E6 degrades p53, E7 inactivates Rb - this is the oncogenic/cancer mechanism (HPV 16/18), not the benign wart mechanism of HPV 6/11

Q26. A man with Entamoeba histolytica cysts on stool test. Which drug eradicates intestinal cysts?

Metronidazole
Diloxanide furoate ✓
Chloroquine
Dihydroemetine

Answer: Diloxanide furoate (Luminal amebicide)

Explanation:

Key concept - Amebicide classification:

Drug Type	Drug	Target	Use
Tissue amebicide	Metronidazole, tinidazole	Trophozoites in tissue	Invasive intestinal/hepatic amoebiasis
Luminal amebicide	Diloxanide furoate, paromomycin, iodoquinol	Cysts + luminal trophozoites	Asymptomatic cyst carriers
Both	Emetine, dehydroemetine	Both	Rarely used now

This patient has CYSTS only (asymptomatic carrier) → needs a luminal amebicide:

Diloxanide furoate (drug of choice for asymptomatic cyst carriers)
Acts directly in the intestinal lumen
Poor systemic absorption (stays in gut)
Eradicates cysts and prevents transmission

Metronidazole is excellent for invasive/symptomatic amoebiasis (tissue trophozoites) BUT:

Poor luminal efficacy against cysts
Does NOT reliably eliminate intestinal cysts
After metronidazole treatment for invasive disease, must follow with diloxanide to eliminate residual luminal cysts

Chloroquine - used for hepatic amoebiasis (concentrates in liver), not for cysts Dihydroemetine - old drug, cardiotoxic, rarely used

Q27. A 65-year-old diabetic, dyslipidemic woman with left MCA territory infarct. Most likely cause?

Atherosclerosis ✓
Cerebral vasculitis
Vascular spasm
Embolism from cardiac mural thrombi

Answer: Atherosclerosis

Explanation:

Risk factors present: Diabetes mellitus + dyslipidemia → these are the two strongest modifiable risk factors for atherosclerosis of large and medium cerebral arteries.

How atherosclerosis causes MCA stroke:

Diabetes + Dyslipidemia
↓
Endothelial dysfunction → LDL oxidation → foam cells → fatty streak
↓
Atherosclerotic plaque (intima-media thickening)
↓
In cerebral/neck vessels (carotid, MCA, basilar)
↓
Plaque rupture → local thrombosis → THROMBOTIC STROKE
OR
Artery-to-artery embolism → embolic stroke
↓
MCA territory infarction → contralateral hemiplegia, aphasia

Large vessel atherosclerotic stroke features:

Gradual onset (may wake up with deficit)
Territorial infarct (MCA, ACA, PCA territory)
No cardiac source of embolism
Evidence of systemic atherosclerosis (peripheral vascular disease, coronary artery disease)

Why not others?

Cardiac embolism: requires cardiac source (AF, MI with mural thrombus, valvular disease) - not mentioned
Vasculitis: rare, usually younger patients, associated with connective tissue disease/infection
Vascular spasm: classic for subarachnoid hemorrhage (not ischemic infarct)

Q28. A 42-year-old woman with oral hyperpigmentation, hypotension, hyponatremia, hyperkalemia, low cortisol, HIGH ACTH. Cause of adrenal insufficiency?

Addison disease ✓
Waterhouse-Friderichsen syndrome
Pituitary failure
Hypothalamic failure

Answer: Addison's Disease (Primary Adrenal Insufficiency)

Explanation:

Distinguishing primary vs secondary/tertiary adrenal insufficiency:

Feature	PRIMARY (Addison's)	SECONDARY (Pituitary)	TERTIARY (Hypothalamic)
ACTH	HIGH (no feedback)	Low	Low
Cortisol	Low	Low	Low
Aldosterone	Low (adrenal destruction)	Normal	Normal
Na/K	Hyponatremia + Hyperkalemia	Hyponatremia only	Hyponatremia only
Skin pigmentation	YES (↑ACTH → MSH stimulation)	No	No
Hypotension	Yes (both glucocorticoid + mineralocorticoid loss)	Mild	Mild

This patient:

HIGH ACTH + LOW cortisol = primary adrenal failure (adrenal glands cannot respond to ACTH)
Hyperkalemia + hyponatremia = mineralocorticoid (aldosterone) deficiency
Oral hyperpigmentation = excess ACTH/POMC → α-MSH → melanocyte stimulation
Chronic course (9 months) = autoimmune Addison's (most common cause in developed countries)

Addison's disease causes:

Autoimmune (~80%) - anti-21-hydroxylase antibodies
Tuberculosis (historically most common globally)
Metastatic cancer
Fungal infections (histoplasmosis)
HIV

Waterhouse-Friderichsen = acute bilateral adrenal hemorrhage from meningococcal septicemia - presents acutely with septic shock and purpuric rash (not chronic 9-month course)

Q29. A 34-year-old woman with painful thyroid after URTI, elevated T3/T4, low TSH. Histological finding?

Scalloped margin of colloids (Graves' disease)
Hurthle cell metaplasia (Hashimoto's)
Formation of germinal centres (Hashimoto's)
Granulomatous inflammation ✓

Answer: Granulomatous inflammation (Subacute/De Quervain's thyroiditis)

Explanation:

This is a classic presentation of Subacute (Granulomatous/De Quervain's) Thyroiditis:

Diagnostic features:

Feature	This Patient
Preceding viral URTI (3 weeks prior)	Classic trigger (coxsackievirus, mumps, measles)
Painful, tender thyroid	Pathognomonic of De Quervain's
Elevated T3/T4 + Low TSH	Transient hyperthyroidism from follicle destruction releasing stored hormones
Diffusely enlarged thyroid	Inflammatory enlargement

Histological hallmark: Granulomatous inflammation

Follicular disruption with colloid spillage
Multinucleated giant cells surrounding disrupted colloid (colloid acts as foreign body)
Lymphocytes and plasma cells (lymphocytic infiltrate)
Epithelioid histiocytes forming granulomas around colloid
Later: fibrosis

Thyroid histology by disease:

Condition	Histology
De Quervain's (subacute)	Granulomatous inflammation, giant cells
Graves' disease	Scalloped colloid, papillary projections, tall epithelium
Hashimoto's	Germinal centers, Hurthle cell metaplasia, lymphocytic infiltrate
Toxic adenoma	Single adenoma, compressed normal tissue

Clinical course of De Quervain's:

Initial hyperthyroidism (weeks 1-8) - stored T3/T4 released
Euthyroid phase
Transient hypothyroidism (depleted stores)
Recovery to normal (~95% of cases)

Treatment: NSAIDs (mild), prednisolone (severe), beta-blockers for symptoms

Q30. A 45-year-old man with polyuria/nocturia, post-urological surgery, narrow right ureter, hydronephrosis, obstructive uropathy. Why polyuria?

Reduced concentrating ability of tubules ✓
Chronic interstitial inflammation
Venous stasis
Reduced glomerular filtration

Answer: Reduced concentrating ability of tubules

Explanation:

Paradoxical polyuria in obstructive uropathy - seemingly contradictory but well-explained:

Mechanism:

Chronic partial obstruction → back pressure in collecting system → transmitted to tubules
Tubular dysfunction develops:
- Collecting duct cells become unresponsive to ADH (nephrogenic diabetes insipidus-like picture)
- Medullary gradient washed out by increased tubular flow and pressure
- Loss of urea transporters → impaired countercurrent multiplication
Result: tubules cannot concentrate urine despite ADH → dilute urine produced in large volumes → polyuria

Additional mechanism:

After relief of obstruction, post-obstructive diuresis occurs - sodium and water that accumulated are excreted en masse

Reduced GFR would cause oliguria/anuria, not polyuria. So reduced GFR explains the initial hydronephrosis/azotemia but NOT the polyuria. The polyuria is specifically from tubular concentrating defect.

Q31. A 35-year-old man with fever, lockjaw, urinary incontinence after stepping on a rusty nail. Suspected tetanus. Which specimen for lab investigation?

Wound swab ✓
Throat swab
Blood specimen
Urine specimen

Answer: Wound swab

Explanation:

Tetanus caused by Clostridium tetani (Gram-positive, spore-forming, obligate anaerobic bacillus):

Key points:

Rusty nail wound → introduced C. tetani spores into anaerobic deep wound environment → spores germinate → vegetative bacteria produce tetanospasmin (TeNT toxin)
Tetanospasmin: blocks inhibitory neurotransmitters (glycine, GABA) at Renshaw cells in spinal cord → spastic/rigid paralysis with autonomic instability

Clinical features:

Trismus (lockjaw) - masseter spasm (first muscle affected)
Risus sardonicus (sardonic smile)
Opisthotonus (back arching)
Autonomic instability (tachycardia, hypertension, sweating)
Bladder/urinary involvement possible

Investigation: Wound swab

Culture from wound may grow C. tetani (Gram-positive bacilli, "tennis racquet" spore appearance)
Anaerobic culture on blood agar
Important: Tetanus is primarily a clinical diagnosis - wound culture is often negative and negative culture does NOT exclude tetanus
The wound swab aids confirmation but treatment should not wait for culture results

Why not others?

Throat swab: C. tetani is not a respiratory pathogen
Blood: bacteremia is NOT a feature of tetanus (it's a toxin-mediated disease, not septicemia)
Urine: no urinary shedding

Q32. A 25-year-old woman with 8 cm right ovarian cyst containing keratinous material, skin, hair, and teeth. Diagnosis?

Mature cystic teratoma ✓
Endometriotic cyst
Follicular cyst
Mucinous cystadenoma

Answer: Mature cystic teratoma (Dermoid cyst)

Explanation:

Pathognomonic features:

Skin (stratified squamous epithelium)
Hair (pilosebaceous units)
Teeth (dental tissue from ectodermal origin)
Keratinous/sebaceous material
Rokitansky protuberance (dermal plug/mural nodule) - the bump from which skin, hair, and teeth grow

This combination = mature cystic teratoma (MCT), also called dermoid cyst.

Teratoma classification:

Type	Age	Behavior	Features
Mature cystic teratoma	Reproductive age (15-40y)	Benign	All 3 germ layers, mostly ectodermal
Immature teratoma	Young (<20y)	Malignant	Neural tissue (neuroepithelium), graded I-III
Monodermal (struma ovarii, carcinoid)	Variable	Mostly benign	Single tissue type

MCT facts:

Most common ovarian germ cell tumor
Most common ovarian tumor in women under 30
Bilateral in 10-15%
Complication: torsion (due to weight - dermoid is heavy from fat/calcification)
Malignant transformation: <2% (usually squamous cell carcinoma)
Diagnosis: ultrasound shows hyperechoic material + shadowing from teeth/calcification; "dermoid mesh" pattern
Treatment: ovarian cystectomy (preserve ovary if possible)

Q33. A 53-year-old man with gradual sensorineural hearing loss, tinnitus. MRI: well-circumscribed neoplasm at cerebellopontine angle. Histology: Antoni A, Antoni B areas, Verocay bodies. Which cells?

Ependymal cell
Oligodendrocyte
Astrocyte
Schwann cell ✓

Answer: Schwann cells (Vestibular Schwannoma / Acoustic Neuroma)

Explanation:

Classic presentation of Vestibular Schwannoma:

Feature	This Patient
Location	Cerebellopontine angle (where CN VIII enters brainstem)
Symptoms	Progressive sensorineural hearing loss + tinnitus (CN VIII compression)
MRI	Well-circumscribed (encapsulated) mass
Histology	Antoni A + Antoni B + Verocay bodies
Cell of origin	Schwann cells of CN VIII (vestibular branch)

Histological features:

Antoni A pattern: compact, cellular areas with spindle cells arranged in palisading nuclear rows
Antoni B pattern: loose, myxoid/hypocellular areas with stellate cells
Verocay bodies: nuclear palisading around acellular eosinophilic zone (like a "sandwich") - pathognomonic of schwannoma

Why not others?

Oligodendrocyte → oligodendroglioma (intraparenchymal, calcification, "fried egg" cells)
Astrocyte → astrocytoma/glioblastoma (intraparenchymal, infiltrating)
Ependymal cells → ependymoma (intraventricular, around 4th ventricle)

Association: Bilateral vestibular schwannomas = Neurofibromatosis Type 2 (NF2) - NF2 gene mutation (chromosome 22)

Treatment: Surgical excision (microsurgery), stereotactic radiosurgery (Gamma Knife), or observation in elderly

Q34. A 22-year-old man with Taenia solium eggs on stool examination. Most common complication?

Intestinal obstruction
Rectal prolapse
Cysticercosis ✓
Microcytic hypochromic anemia

Answer: Cysticercosis

Explanation:

This is a critical distinction about Taenia solium life cycle:

T. solium has TWO ways to infect humans:

Infection Type	Route	Result
Taeniasis (adult worm)	Eat undercooked pork containing cysticerci	Adult tapeworm in intestine (benign, usually asymptomatic)
Cysticercosis (larval stage)	Ingest T. solium eggs (fecal-oral from contaminated food/water/autoinfection)	Larvae (cysticerci) in tissues

This patient has EGGS in stool - meaning he/she is already shedding eggs as an intestinal carrier - and is at risk of autoinfection (swallowing own eggs → cysticercosis) or infecting others.

Why cysticercosis is the most common/important complication:

Eggs ingested → oncospheres hatch in intestine → penetrate gut wall → hematogenous spread to:
- Brain (neurocysticercosis - most common) - seizures, hydrocephalus, focal deficits
- Eye (visual disturbance, blindness)
- Muscle, subcutaneous tissue
- Liver, heart

Neurocysticercosis is the most common cause of acquired epilepsy worldwide in endemic areas (Latin America, Africa, South/Southeast Asia)

Why not intestinal obstruction?

T. solium adult worms are smaller than T. saginata and less likely to cause obstruction
Intestinal obstruction is more associated with Ascaris lumbricoides (very large worms, cause physical blockage)
The question asks for the most common complication with T. solium specifically - and that is cysticercosis (from egg ingestion), not obstruction

Summary Table - All 34 Questions

Q	Answer	Key Concept
4	Ovary	FSH/LH lost 2nd in hypopituitarism sequence
5	Proteus mirabilis	Urease+, swarming, alkaline urine, catheter UTI
6	Urine examination	Terminal-spined eggs in urine (midday)
7	PrPSc converts PrPC	Most common sporadic CJD mechanism
8	Low D2 affinity	Clozapine avoids nigrostriatal D2 blockade → no TD
9	Collecting duct	Aldosterone receptor (MR) in principal cells of CCD
10	Malfunctioning BBB	Vasogenic edema = BBB breakdown + plasma protein leak
11	Inhibition of Ca2+ absorption	Steroids antagonize VitD in gut + increase renal Ca loss
12	History of C-section	Scarred uterus + oxytocin = uterine rupture risk
13	Acute adrenal insufficiency	HPA suppression → adrenal atrophy → crisis on withdrawal
14	Candida albicans	Cottage cheese discharge, vulvar itch
15	Autoimmune demyelination	MS: autoreactive T cells against myelin, oligoclonal bands
16	Ingestion of metacercaria	Fasciola on aquatic vegetation - NOT cercaria
17	Subepithelial deposits	Membranous nephropathy - "spike and dome"
18	Circulatory system diseases	Cardiovascular = #1 NCD killer in Malaysia
19	Case-control	Disease → look backward for exposure; OR
20	Increases GABA inhibitory effect	BZD: increase Cl- channel opening FREQUENCY
21	Somatropin	Recombinant GH for Turner syndrome short stature
22	Lesion culture (gold standard)	H. ducreyi on selective agar
23	Irrespective of pregnancy duration	WHO MMR definition
24	RBC casts	Post-streptococcal GN → glomerular hematuria
25	HPV infects surface epithelial layer	Productive replication in upper/surface layers
26	Diloxanide furoate	Luminal amebicide for asymptomatic cyst carrier
27	Atherosclerosis	DM + dyslipidemia = large vessel thrombotic stroke
28	Addison's disease	Primary AI: high ACTH + pigmentation + hyperkalemia
29	Granulomatous inflammation	De Quervain's thyroiditis - giant cells, post-viral
30	Reduced tubular concentrating ability	Tubular ADH resistance → dilute urine → polyuria
31	Wound swab	C. tetani from anaerobic wound culture
32	Mature cystic teratoma	Skin + hair + teeth = dermoid cyst
33	Schwann cells	Vestibular schwannoma: Antoni A/B + Verocay bodies
34	Cysticercosis	T. solium EGGS → larval invasion of brain/tissues

35. A 3-year-old boy is diagnosed with leukaemia and is on immunosuppressive therapy. Which of the following vaccines should be avoided in the above patient? Tetanus vaccine Diphtheria vaccine Mumps vaccine Hepatitis vaccine 36. A 20-yerar-old man newly diagnosed with Type 1 Diabetes Mellitus is prescribed with insulin. The house officer demonstrates the injection technique and instructs to avoid the same injection site while administering the daily dose. Which of the following side effects is most likely avoided by the above instruction to the patient? Hypokalaemia Hypoglycaemia Lipodystrophy Hyperalgesia 37. A 52-year-old woman presents with acute right flank pain. Imaging studies reveal stones in the right pelvis of her kidney. Laboratory investigation reveals hypercalcemia and eleva ed level of parathyroid hormone. Nuclear imaging shows increased uptake in a solita y parathyroid gland. Whic of the following disorders is the most likely cause of hypercalcemia in this patie t? Parathyroid hyperplasia Parathyroid adenoma Parathyroid atrophy Parathyroid carcinoma 38. A 40-year-old woman diagnosed with partial epilepsy is prescribed with antiepileptic drugs including gabapentin for the last six months and the seizure is under control now. Which of the following side effects is most likely experienced due to the above- mentioned drug? Somnolence Nystagmus Fatigue Dizziness 39. A 13-year-old boy presents with sudden left-sided testicular pain. Which of the following testicular lesions have to be excluded first in the above patient? Orchitis Testicular tumor Epididymitis Testicular torsion 40. A 39-year-old woman is diagnosed with grade 2 invasive ductal carcinoma and meta tasis to axillary lymph nodes. The tumour shows HER2+ positivity after immt ohistochemistry confirmation. She is prescribed a specific anticancer drug. Whic of the following anticancer drugs is prescribed to this patient? Trastuzumab Cisplatin Anastrozole tamoxifen 41. A group of year 2 medical students were discussing on the reason behind contraindication of opioid analgesic in patients with undiagnosed abdominal pain. Which of the following statements is most probable reason to avoid prescribing the above drug? To prevent abdominal perforation To prevent damage to internal organs To prevent obstruction of blood flow To prevent masking of visceral pain 42. A malnourished two-year-old girl (weight 4.75 kg) who is undergoing the proper nutritional programme gains 32% more weight in three weeks (weight 6.28kg). Which of the following indicators accurately determines the nutritional status of the girl? Anthropometry Vital signs Clinical examination Biochemical tests 43. A 35-year-old woman who is married for 3 years consults an infertility clinic as she fails to co ceive. After investigation, she is diagnosed with anovulatory infertility. Clomiphene citrat is prescribed to the patient. Whic of the following statements best describes the mode of action of the prescribed drug? It inhibits the synthesis of oestrogen. It inhibits follicle stimulating hormone release. It down regulates gonadotropin releasing hormone receptors. It selectively antagonises oestrogen receptor. 44. A 32-year-old man with multiple sexual partners is suspected to have HIV infection. Blood specimen from the patient is sent to the laboratory for investigations. Which of the following antigens should be identified to detect this infection at an early stage? Glycoprotein 40 Protein 24 Glycoprotein 120 Protein 17 45. A 11-year-old boy presents with rectal bleeding, abdominal pain and fatigue. On examination, there are dark blue macules on the mucocutaneous junctions, palmar surfaces of the hands, genitalia, and perianal region. Colonoscopy showed multiple exophytic polyps throughout the colon. Biopsy confirms Peutz-Jeghers polyp. Which of the following histopathological features is most significant for the above condition? Mixed glandular structure and smooth muscle Pseudo-invasive epithelial misplacement Superficial columnar and goblet cells Inflammatory debris accumulate within crypts 46. A 45-year-old male smoker who is a diabetic, presents with dysphagia and heartburn for the past 3 months. Upper GI endoscopy reveals redness in the lower end of oesophagus. Biopsy reveals basal zone hyperplasia, elongation of lamina propria papillae and infiltration of epithelium by eosinophils. He is diagnosed with oesophagitis. Which of the following agents is the most likely cause of oesophagitis in this patient? Gastric acid Candida albicans Tobacco Herpes Simplex Virus 47. A 65-year-old male presents to Outpatient Clinic with the chief complaint of painless haematuria. The urine cytologic findings reveals clusters of pleomorphic malignant cells. Cystoscopy reveals a broad-based solitary nodular mass lesion on the anterior bladder wall. Which of the following histologic subtypes of neoplasm is most likely to be present in this patient? Adenocarcinoma Squamous cell carcinoma Papillary urothelial carcinoma Clear cell carcinoma 48. A stray dog bites a 11-year-old boy. He fails to get the post-exposure immunisation. After two months, he presents with neurological signs and a diagnosis of rabies is made. Which of the following factors is most likely to play the main role in the viral spread to the central nervous system in this case? Migration of infected epidermal dendritic cells. Inoculation of the virus in deep muscles. Absence of an early immune response. Presence of the viruses in blood. 49. A 45-year-old woman presents to the hospital with multiple hypopigmented patches on her back with loss of sensation over the patches for the past few months. The attending doctor suspects that she is having leprosy. Which of the following initial investigations is the most appropriate to establish the diagnosis? Blood culture Skin biopsy culture Detection of antibody Acid fast staining of the skin scrapping 50. A 58-year-old hypertensive patient is treated with high dose intravenous gentamicin for a systemic infection in the hospital. After two days, the patient complains of haematuria which progressed rapidly to anuric renal insufficiency. He is suspected with iatrogenic nephrotoxicity. Which of the following mechanisms best describes the nephrotoxicity of the above administered drug? Tubular-cell toxicity Drug induced crystal nephropathy Altered intrarenal haemodynamics Thrombotic microangiopathy 51. A 35-year-old woman with known history of cholelithiasis presents with epigastric pain associated with fever for 3 days. She is suspected to have acute cholecystitis. Which of the following findings on physical examination is most suggestive of the diagnosis? Abdominal rigidity Epigastric tenderness Murphy's sign Jaundice of breath on exertion. Full blood count shows evidence of blood dyscrasias. She has history of taking sulphamethoxazole combination for treatment of recurrent bacillary dysentery in the past two weeks. Which of the following reasons is most likely cause of presenting symptoms in the above patient? Complications of the infection Poor iron absorption due to inflammatory bowel disease Sulpha drug induced anaemia Delayed recovery from infection 53. A 44-year-old man presents to the clinic with complaints of abdominal pain and bloody diarrhoea for three days. Stool examination shows leukocytes, erythrocytes and spiral, girdle shaped bacteria. A diagnosis of bloody diarrhoea caused by Campylobacter jejuni is made. Which of the following virulence factors is most significant to cause inflammation in this patient? Cytolethal distending toxin Capsular polysaccharide Adhesins Flagellins 54. Disease is an outcome of the host-pathogen interaction wherein pathogens can express a wide range of virulence. Which of the following statements best describe virulence for the above scenario? Ability to cause severe disease Ability to evoke an immune response Ability to cause death Ability to cause clinical disease 55. During a food poisoning outbreak, a medical officer looks for statistical evidence for the association between fried rice intake and food poisoning. The obtained p value is 0.4. Which of the following conclusions could be derived from the above scenario? Those who did not eat fried rice had food poisoning. Fried rice was associated with food poisoning. The rate of food poisoning is 40% No association between taking fried rice and food poisoning. 56. A 45-year-old patient is diagnosed with meningitis due to Cryptococcus neoformans. The physician starts the patient with amphotericin B and flucytosine. Which of the following statements best explains the rationale of the above drug combination? It reduces the side effects. It prevents resistance to antifungal agents. It enhances spectrum of antifungal activity. It improves the penetration of drug into CNS. 57. A 35-year-old man presents with fever and inguinal lymphadenopathy. Based on laboratory investigations, he is diagnosed with filariasis and started with an antihelminth drug. Which of the following antihelminths is the drug of choice for this patient? Pyrantel pamoate Albendazole Diethylcarbamazine Praziquantel 58. A 31-year-old woman presents to the clinic with whitish vaginal discharge and dyspareunia. Investigations confirms chronic cervicitis. Which of the following changes is a major diagnostic indicator of chronic cervicitis? Reactive atypia of the endocervical epithelium Oedema of the subepithelial matrix Haemorrhage of the submucosal region Mononuclear cells infiltrate in squamo-columnar junction 59. A 52-year-old man presents to the clinic with watery diarrhoea and abdominal bloating for the past 2 days. Stool examination shows pear-shaped, flagellated, motile organisms. Which of the following organisms is the most likely cause of the above condition? Entamoeba histolytica Giardia lamblia Entamoeba coli Balantidium coli 60. A 63-year-old obese, hypertensive woman visits Gynaecology Clinic because of post- menc ausal vaginal bleeding for the past three days. She attained menopause at 54 year s of age. Bimanual pelvic examination shows that the uterus is normal in size, with no p lpable adnexal masses. An endometrial biopsy reveals a neoplastic lesion of epith lial origin. Whic of the following types of neoplasms is most likely to be found in the endometrial biops specimen? Squamous cell carcinoma Adenocarcinoma Choriocarcinoma Leiomyosarcoma

Here are all 26 questions (Q35-Q60) answered fully:

Q35. A 3-year-old boy with leukemia on immunosuppressive therapy. Which vaccine should be avoided?

Tetanus vaccine
Diphtheria vaccine
Mumps vaccine ✓
Hepatitis vaccine

Answer: Mumps vaccine (MMR - live attenuated)

Explanation:

The fundamental principle: live vaccines are absolutely contraindicated in immunocompromised patients.

Vaccine classification:

Type	Examples	Safe in Immunocompromised?
Live attenuated	MMR, Varicella (VZV), BCG, OPV, Yellow fever, LAIV (nasal flu), Rotavirus, Oral typhoid	NO - CONTRAINDICATED
Inactivated/killed	IPV (injected polio), Hepatitis A, Hepatitis B, Influenza (injected), Typhoid Vi	YES - Safe
Toxoid	Tetanus, Diphtheria (Td/Tdap)	YES - Safe
Subunit/recombinant	Hepatitis B, HPV, Pertussis (acellular), Pneumococcal	YES - Safe

Why live vaccines are dangerous in immunocompromised:

The attenuated organism cannot be controlled by the impaired immune system
Can cause vaccine-strain disseminated disease (e.g., vaccine-strain measles encephalitis, disseminated VZV from varicella vaccine)
Can be fatal in leukemia/lymphoma, post-transplant, HIV (CD4 <200), on high-dose steroids/chemotherapy

Mumps vaccine = part of MMR (Measles-Mumps-Rubella) = live attenuated = CONTRAINDICATED

Tetanus and Diphtheria vaccines are toxoids (inactivated toxins) - safe to give. Hepatitis B vaccine is a recombinant subunit vaccine - safe to give.

Q36. A 20-year-old Type 1 diabetic on insulin - instructed to avoid the same injection site. What side effect is avoided?

Hypokalemia
Hypoglycemia
Lipodystrophy ✓
Hyperalgesia

Answer: Lipodystrophy

Explanation:

Lipodystrophy = abnormal distribution of adipose tissue at insulin injection sites, caused by the local lipogenic and/or lipolytic effects of insulin.

Two forms:

Form	Description	Mechanism
Lipohypertrophy (more common)	Rubbery, fatty lump at injection site	Insulin's anabolic/lipogenic effect → local adipocyte hypertrophy
Lipoatrophy (less common, older insulins)	Concave depression at injection site	Immune-mediated fat atrophy

Why rotation matters:

Repeated injection at the same site → lipohypertrophy develops (painless, soft lump)
Lipohypertrophic tissue has altered vascularity and fibrosis → erratic, unpredictable insulin absorption from that site → poor glycemic control (blood glucose peaks and troughs)
Rotating sites (abdomen, thigh, buttock, upper arm) prevents this accumulation

Recommended rotation:

Same general body region each day (e.g., always abdomen for morning dose)
Rotate within the region by ~2 cm each injection
Do NOT inject into lipohypertrophic areas

Why not the others?

Hypoglycemia: rotation actually helps avoid hypoglycemia from erratic absorption
Hypokalemia: insulin can cause hypokalemia by driving K+ into cells, but this is unrelated to injection site rotation
Hyperalgesia: no direct link to injection site rotation

Q37. A 52-year-old woman with right flank pain, renal stones, hypercalcemia, elevated PTH, increased uptake in a SINGLE parathyroid gland on nuclear imaging. Cause?

Parathyroid hyperplasia
Parathyroid adenoma ✓
Parathyroid atrophy
Parathyroid carcinoma

Answer: Parathyroid adenoma (Primary Hyperparathyroidism)

Explanation:

Key diagnostic clue: "Solitary parathyroid gland" with increased uptake on nuclear scan (Tc-99m sestamibi scan)

This is the hallmark of a single functioning parathyroid adenoma.

Primary Hyperparathyroidism - causes:

Cause	Frequency	Nuclear Scan	Other Features
Solitary adenoma	~85%	Single gland uptake	Sporadic, benign
Multigland hyperplasia	~15%	All 4 glands enlarged	Associated with MEN1, MEN2A
Double adenoma	~2-3%	Two glands	-
Carcinoma	<1%	Single gland, large	Very high PTH, palpable neck mass, bone invasion

Classic presentation of primary hyperparathyroidism:

"Bones, Stones, Groans, and Psychic Moans":

Bones: osteitis fibrosa cystica, subperiosteal bone resorption (radial aspect of middle phalanx), pathological fractures
Stones: nephrolithiasis (calcium oxalate/phosphate stones) - as in this patient
Groans: GI symptoms (nausea, constipation, peptic ulcer - PTH stimulates gastrin)
Psychic moans: depression, cognitive changes, fatigue

Lab findings:

Hypercalcemia (↑Ca2+)
Elevated PTH (inappropriately normal or high for the calcium level)
Hypophosphatemia (PTH inhibits PCT phosphate reabsorption)
Hypercalciuria (↑renal Ca filtration despite PTH-stimulated reabsorption)
Elevated alkaline phosphatase (bone turnover)

Treatment: Parathyroidectomy (surgical removal of adenoma = curative)

Q38. A 40-year-old woman with partial epilepsy on gabapentin for 6 months. Which side effect is most likely?

Somnolence ✓
Nystagmus
Fatigue
Dizziness

Answer: Somnolence (though all 4 are gabapentin side effects)

Explanation:

Gabapentin (structural analogue of GABA, but does NOT act on GABA receptors):

Mechanism of action:

Binds α2δ subunit of voltage-gated calcium channels in CNS
Reduces presynaptic Ca2+ influx → decreased excitatory neurotransmitter release (glutamate, substance P)
Used for: partial seizures, neuropathic pain, postherpetic neuralgia, fibromyalgia, anxiety (off-label)

Side effects of gabapentin:

Side Effect	Frequency
Somnolence/sedation	Very common (most common)
Dizziness/vertigo	Very common
Ataxia	Common
Fatigue	Common
Peripheral edema	Common
Weight gain	Common
Nystagmus	Less common
Cognitive impairment	Common

Somnolence is the most common and most clinically significant side effect of gabapentin, occurring in up to 19-30% of patients. It is particularly problematic in elderly patients (fall risk). It often improves with time or dose reduction.

Note on Nystagmus: Nystagmus is more classically associated with phenytoin toxicity (the classic toxicity triad: Nystagmus → Ataxia → Drowsiness). Gabapentin can cause nystagmus but it is not the primary/most common side effect.

Q39. A 13-year-old boy with sudden left-sided testicular pain. Which lesion must be EXCLUDED FIRST?

Orchitis
Testicular tumor
Epididymitis
Testicular torsion ✓

Answer: Testicular torsion (MUST EXCLUDE FIRST - surgical emergency)

Explanation:

Testicular torsion = urological emergency that must be excluded before all other diagnoses.

Why testicular torsion is the priority:

Time to detorsion	Testicular salvage rate
<6 hours	~90-100%
6-12 hours	~50%
12-24 hours	~10%
>24 hours	<10% (usually orchiectomy needed)

Testicular torsion profile:

Feature	Detail
Age	Bimodal: neonates and 12-18 years (adolescent peak)
Cause	Bell-clapper deformity (high investment of tunica vaginalis → testicle can rotate freely)
Presentation	Sudden onset severe scrotal pain, often during sleep/activity, nausea/vomiting
Exam	Swollen, tender, high-riding testicle; transverse lie; absent cremasteric reflex (most sensitive sign)
Doppler US	Absent/reduced testicular blood flow
Treatment	Immediate surgical exploration + bilateral orchiopexy

Differential diagnosis of acute scrotal pain:

Condition	Age	Key Feature
Testicular torsion	12-18y	Absent cremasteric reflex, sudden onset
Epididymo-orchitis	Sexually active adults	Gradual onset, fever, dysuria, Prehn's sign positive
Torsion of appendix testis	7-12y	"Blue dot sign"
Orchitis (mumps)	Post-pubertal	Bilateral, fever, parotitis
Testicular tumor	20-35y	Painless mass (usually)

Absent cremasteric reflex (stroking inner thigh → no ipsilateral testicular elevation) = most reliable clinical sign of torsion.

Q40. A 39-year-old woman with Grade 2 invasive ductal carcinoma, axillary node metastasis, HER2+ on IHC. Which anticancer drug is prescribed?

Trastuzumab ✓
Cisplatin
Anastrozole
Tamoxifen

Answer: Trastuzumab (Herceptin)

Explanation:

HER2 (Human Epidermal Growth Factor Receptor 2):

Proto-oncogene on chromosome 17q12
Encodes a transmembrane receptor tyrosine kinase (ErbB2)
Amplified/overexpressed in ~20-25% of breast cancers
HER2+ = poor prognosis WITHOUT targeted therapy; good response WITH targeted therapy

Trastuzumab (Herceptin):

Humanized monoclonal antibody targeting the extracellular domain IV of HER2
Mechanisms:
1. Blocks HER2 signaling (PI3K/Akt and MAPK pathways → reduced proliferation)
2. ADCC (Antibody-Dependent Cell-mediated Cytotoxicity) - NK cells destroy HER2+ tumor cells
3. Prevents HER2 receptor shedding
4. Reduces angiogenesis

Breast cancer targeted therapy:

Receptor Status	Drug	Class
HER2+	Trastuzumab, Pertuzumab, T-DM1	HER2 targeted
ER+/PR+ (hormone receptor positive)	Tamoxifen (pre-menopausal), Anastrozole/Letrozole (post-menopausal)	Hormonal
Triple negative (ER-/PR-/HER2-)	Chemotherapy, PARP inhibitors	No targeted therapy

Why not others?

Tamoxifen: SERM, blocks estrogen receptor → for ER-positive breast cancer, not HER2+
Anastrozole: aromatase inhibitor → for ER+, post-menopausal breast cancer
Cisplatin: platinum-based chemotherapy → for triple-negative or BRCA-mutated breast cancer

Important side effect of trastuzumab: Cardiotoxicity (reversible dilated cardiomyopathy, reduced LVEF) - requires cardiac monitoring (ECHO or MUGA scan)

Q41. Medical students discuss why opioids are contraindicated in undiagnosed abdominal pain. Most probable reason?

To prevent abdominal perforation
To prevent damage to internal organs
To prevent obstruction of blood flow
To prevent masking of visceral pain ✓

Answer: To prevent masking of visceral pain

Explanation:

Traditional teaching (classical exam answer):

Opioids are traditionally contraindicated in undiagnosed acute abdominal pain because:

Opioids are potent analgesics that abolish visceral pain
Without pain, the clinician loses the key diagnostic sign needed to:
- Locate the pathology (RIF pain = appendicitis, RUQ = cholecystitis)
- Assess peritoneal signs (guarding, rebound tenderness, rigidity)
- Track disease progression or improvement
This could lead to delayed diagnosis and treatment of life-threatening conditions (appendicitis → perforation, ischemic bowel, ruptured ectopic pregnancy)

Modern evidence-based perspective (important to know):

Multiple RCTs and meta-analyses have shown that opioid analgesia in acute abdominal pain does NOT significantly impair diagnostic accuracy
Current ACEP (American College of Emergency Physicians) guidelines support early analgesia in acute abdominal pain
However, for exam purposes, the traditional answer remains: "masking of visceral pain"

Why not the other options?

Abdominal perforation: opioids do not cause perforation - they may mask the pain of a perforation
Damage to internal organs: opioids have no direct toxic effect on abdominal organs
Obstruction of blood flow: opioids cause peripheral vasodilation, not vascular obstruction

Q42. A malnourished 2-year-old girl weighing 4.75 kg gains 32% weight to 6.28 kg in 3 weeks. Which indicator accurately determines nutritional status?

Anthropometry ✓
Vital signs
Clinical examination
Biochemical tests

Answer: Anthropometry

Explanation:

Nutritional assessment methods:

Method	Examples	Type	Limitation
Anthropometry	Weight, height, MUAC, BMI, skin fold thickness	Direct, objective, quantitative	Requires calibrated equipment
Clinical examination	Wasting, edema, hair changes, skin changes	Indirect, subjective	Late signs, observer-dependent
Biochemical	Albumin, prealbumin, transferrin, Hb, zinc	Indirect - reflects metabolic state	Affected by non-nutritional factors
Dietary assessment	24-hour recall, food frequency	Indirect - reflects intake	Self-reporting bias
Vital signs	Not a nutritional tool	Non-specific	Not nutritional

Anthropometry is the most accurate DIRECT method because:

Quantitative (actual measurements, not subjective)
Reproducible (same measurements by different observers if standardized)
Sensitive (detects changes over time - as demonstrated in this case: 32% weight gain)
Uses reference standards (WHO growth charts) for comparison
The question itself demonstrates anthropometry: serial weight measurements tracking nutritional response

Anthropometric indices for children:

Weight-for-age: underweight (global malnutrition)
Height-for-age: stunting (chronic malnutrition)
Weight-for-height: wasting (acute malnutrition)
MUAC (Mid-upper arm circumference): field screening
BMI-for-age: overall adiposity

Biochemical tests reflect the body's metabolic response (e.g., low albumin) but are indirect and influenced by non-nutritional factors (infection raises acute phase proteins, reducing albumin independent of nutrition).

Q43. A 35-year-old woman with anovulatory infertility prescribed clomiphene citrate. Best description of mechanism of action?

It inhibits the synthesis of oestrogen
It inhibits follicle stimulating hormone release
It downregulates gonadotropin-releasing hormone receptors
It selectively antagonises oestrogen receptor ✓

Answer: Selectively antagonises oestrogen receptor (at hypothalamus)

Explanation:

Clomiphene citrate:

Classified as a Selective Estrogen Receptor Modulator (SERM)
Has both estrogen agonist and antagonist properties depending on tissue
In the context of ovulation induction: acts as estrogen ANTAGONIST at hypothalamus

Mechanism step by step:

Clomiphene blocks hypothalamic estrogen receptors
          ↓
Hypothalamus cannot detect circulating estrogen
          ↓
No negative feedback signal received
          ↓
Hypothalamus increases GnRH pulse frequency and amplitude
          ↓
Pituitary releases MORE FSH and LH
          ↓
FSH stimulates follicular development
          ↓
Dominant follicle grows → estrogen rises → LH surge → OVULATION

Key concept: Clomiphene does NOT inhibit FSH - it INCREASES FSH by blocking negative feedback. It does NOT downregulate GnRH receptors - it actually upregulates the GnRH-pituitary axis.

Clomiphene tissue effects:

Tissue	Effect	Consequence
Hypothalamus	Antagonist (blocks ER)	↑GnRH → ↑FSH/LH → ovulation
Endometrium	Antagonist	Thin endometrium (limits implantation)
Cervical mucus	Antagonist	Thick, hostile mucus
Vaginal epithelium	Agonist	Maturation
Bone	Partial agonist	Mild protective effect

Side effects: Hot flashes (from anti-estrogen effect), ovarian cysts, multiple pregnancies (twins ~8%), visual disturbances (stop drug immediately if visual symptoms occur), ovarian hyperstimulation syndrome (OHSS - rare with clomiphene)

Q44. A 32-year-old man suspected of HIV infection. Which antigen should be identified for EARLY stage detection?

Glycoprotein 40 (gp41)
Protein 24 (p24) ✓
Glycoprotein 120 (gp120)
Protein 17 (p17)

Answer: Protein 24 (p24 antigen)

Explanation:

HIV structure and protein functions:

Protein	Location	Function	Detection
p24	Capsid (core)	Structural protein forming viral core	Early HIV marker - appears first
p17	Matrix (beneath envelope)	Structural, viral assembly	Late, after seroconversion
gp120	Envelope (surface)	Binds CD4 and co-receptors (CCR5/CXCR4)	Antibody appears 4-8 weeks
gp41	Envelope (transmembrane)	Membrane fusion	Antibody appears 4-8 weeks
p31	Integrase	Viral integration	-
p51/p66	Reverse transcriptase	Viral replication	-

HIV testing window periods:

Test Generation	Detects	Window Period
1st gen (ELISA)	Anti-HIV IgG	6-12 weeks
2nd gen	Anti-HIV IgG (improved)	4-8 weeks
3rd gen	Anti-HIV IgG + IgM	3-4 weeks
4th gen (current standard)	Anti-HIV IgG/IgM + p24 antigen	~2 weeks
NAT/NAAT	HIV RNA (viral load)	~10-12 days (earliest)

p24 antigenemia occurs during acute/primary HIV infection (2-4 weeks post-exposure) - BEFORE antibodies develop (window period). This makes p24 the earliest serological marker of HIV infection.

Timeline of HIV markers:

Exposure → [10-12 days] → HIV RNA detectable
         → [2-4 weeks] → p24 antigen detectable (4th gen test)
         → [4-8 weeks] → Anti-gp120/gp41 antibodies appear
         → [3-6 months] → Anti-p17 antibodies (late)

The 4th generation HIV combo test detects both p24 antigen + antibodies, dramatically shortening the diagnostic window.

Q45. An 11-year-old boy with rectal bleeding, dark macules on lips/mucosa, and Peutz-Jeghers polyps on biopsy. Most significant histopathological feature?

Mixed glandular structure and smooth muscle
Pseudo-invasive epithelial misplacement
Superficial columnar and goblet cells ✓
Inflammatory debris accumulate within crypts

Answer: Superficial columnar and goblet cells (over arborizing smooth muscle core)

Explanation:

Peutz-Jeghers Syndrome (PJS):

Autosomal dominant
STK11/LKB1 gene mutation (tumor suppressor, chromosome 19p13)
Hamartomatous polyps throughout the GI tract (predominantly small intestine)
Mucocutaneous pigmentation: dark macules on lips, buccal mucosa, palms, soles, genitalia, perioral - as in this patient

Histopathology of Peutz-Jeghers polyp:

Surface: NORMAL INTESTINAL EPITHELIUM
         ↓
    [Columnar cells + Goblet cells]
         ↓
    ARBORIZING SMOOTH MUSCLE CORE
    (branching extensions of muscularis mucosae)
         ↓
    LAMINA PROPRIA (normal)

Key histological features:

Non-dysplastic epithelium - no cytological atypia (hamartoma, not adenoma)
Superficial columnar and goblet cells covering the polyp surface (= normal colonic/intestinal mucosa)
Arborizing (tree-like branching) smooth muscle from muscularis mucosae - pathognomonic finding
Mixed glandular and smooth muscle architecture

"Pseudo-invasive epithelial misplacement" - this is seen in PJS polyps but represents a benign phenomenon (mechanical invagination of epithelium into submucosa due to torsion/traction), not true malignant invasion. It can mimic carcinoma (important diagnostic pitfall).

Clinical complications of PJS:

Intussusception (leading cause of rectal bleeding in these patients)
Obstruction
Increased cancer risk: GI cancers (colorectal, stomach, small bowel), and extra-intestinal (pancreas, breast, ovary, cervix)

Q46. A 45-year-old male smoker with diabetes, dysphagia, heartburn. Endoscopy shows redness in lower esophagus. Biopsy shows basal zone hyperplasia, elongated papillae, eosinophil infiltration. Diagnosed with esophagitis. Cause?

Gastric acid ✓
Candida albicans
Tobacco
Herpes Simplex Virus

Answer: Gastric acid (Reflux Esophagitis)

Explanation:

The biopsy findings are the key:

Histological Feature	Significance
Basal zone hyperplasia	Increased cell turnover from repeated acid injury → repair response
Elongation of lamina propria papillae (>2/3 of epithelial thickness)	Connective tissue papillae extend upward into squamous epithelium - sign of mucosal regeneration
Eosinophil infiltration	Inflammatory response to acid injury (also seen in eosinophilic esophagitis - but different distribution)

These three features together = histopathological hallmarks of GERD-related reflux esophagitis.

Risk factors present in this patient:

Diabetes (gastroparesis → delayed gastric emptying → increased reflux)
Smoking (reduces LES pressure, impairs esophageal clearance, reduces mucosal bicarbonate secretion)
Obesity (increased intra-abdominal pressure)
Heartburn (symptom of acid reflux)
Redness at lower end of esophagus (endoscopic esophagitis = erythema, erosions)

Esophagitis type comparison:

Type	Cause	Endoscopy	Histology	Risk factor
Reflux	Gastric acid	Redness, erosions at lower end	Basal hyperplasia, papillae elongation, eosinophils	GERD, obesity, diabetes, smoking
Candida	C. albicans	White plaques	Pseudohyphae	Immunocompromised
HSV	Herpesvirus	Vesicles → punched-out ulcers	Cowdry A inclusions, multinucleated giant cells	Immunocompromised
CMV	Cytomegalovirus	Large shallow ulcers	Owl-eye inclusions	Immunocompromised
Eosinophilic	Allergic	Rings, linear furrowing	≥15 eosinophils/HPF in mid-esophagus	Atopy

Note: The eosinophils in reflux esophagitis occur at the distal esophagus (as here), while eosinophilic esophagitis has eosinophils throughout (mid and proximal esophagus, ≥15/HPF).

Q47. A 65-year-old man with painless hematuria. Urine cytology shows pleomorphic malignant cells. Cystoscopy shows a broad-based solitary nodular mass on anterior bladder wall. Histologic subtype?

Adenocarcinoma
Squamous cell carcinoma
Papillary urothelial carcinoma ✓ (but see explanation)
Clear cell carcinoma

Answer: Urothelial (Transitional Cell) Carcinoma - Papillary type

Explanation:

Key clinical features:

Painless hematuria (most common presentation of bladder cancer - "hematuria until proven otherwise")
Positive urine cytology (malignant cells)
Bladder mass on cystoscopy
Male, 65 years old (bladder cancer: M:F = 3-4:1, peak age 60-70)

Bladder cancer types by frequency:

Type	Frequency	Feature
Urothelial/TCC (Transitional Cell Carcinoma)	~90%	Most common
Squamous cell carcinoma	~5%	Associated with schistosomiasis, chronic irritation, catheter
Adenocarcinoma	~2%	Urachal remnant, exstrophy
Small cell carcinoma	<1%	Aggressive, neuroendocrine

Urothelial carcinoma morphology:

Form	Description
Papillary (most common, ~70%)	Frond-like exophytic projections, broad base or narrow stalk
Flat (CIS - carcinoma in situ)	Flat, high-grade, non-invasive but high malignant potential
Invasive	Penetrates muscularis propria (T2+)

"Broad-based solitary nodular mass" = papillary urothelial carcinoma (non-papillary/sessile morphology is also urothelial carcinoma).

Risk factors for bladder TCC:

Smoking (most important risk factor, 50% of cases) - carcinogens excreted in urine
Aniline dyes (rubber, textile industry) - benzidine, 2-naphthylamine
Cyclophosphamide
Pelvic radiation
Chronic UTI/stones (→ squamous cell carcinoma)
Schistosoma haematobium (→ squamous cell carcinoma specifically)

Q48. A stray dog bites an 11-year-old boy. No post-exposure prophylaxis. Two months later develops neurological signs. Diagnosed with rabies. What factor plays the MAIN role in viral spread to CNS?

Migration of infected epidermal dendritic cells
Inoculation of the virus in deep muscles
Absence of an early immune response
Presence of viruses in blood (listed, but actual answer is retrograde axonal transport)

Answer: Retrograde axonal transport (the listed answer most consistent with this is "absence of early immune response" or the intended answer is about the mechanism)

Explanation:

Let me carefully analyze each option in context of rabies pathogenesis:

Rabies virus spread to CNS - step by step:

Dog bite → Rabies virus inoculated into muscle/subcutaneous tissue
           ↓
Virus replicates locally in MUSCLE cells (incubation period weeks-months)
           ↓
Binds to NICOTINIC ACh RECEPTORS and NCAM at neuromuscular junction
           ↓
Enters peripheral motor/sensory nerve terminals
           ↓
RETROGRADE AXONAL TRANSPORT (fast axonal transport, ~50-100mm/day)
           ↓
Travels up peripheral nerves to spinal cord → brainstem → brain
           ↓
Once in CNS → viral replication in neurons → encephalitis
           ↓
Centrifugal spread: brain → salivary glands, cornea, skin

Analyzing options:

Migration of infected epidermal dendritic cells: Minor role in initial viral uptake - not the main spread mechanism
Inoculation in deep muscles: Proximity to NMJ enhances spread, but bites near face/head have shorter incubation due to shorter nerve distance - this is relevant but not the PRIMARY spread mechanism
Absence of early immune response: Partially true - rabies has evolved to evade immune detection during peripheral nerve transport (inside axons = immunologically privileged), explaining why post-exposure prophylaxis must be given early before virus enters CNS
Presence of virus in blood (viremia): Rabies does NOT spread hematogenously - this is incorrect

Correct mechanism = Retrograde axonal transport - this is not explicitly listed as an option. The "absence of early immune response" best explains why the virus successfully reaches the CNS (while inside axons, it is hidden from immune surveillance), and the failure of post-exposure prophylaxis in this case.

The "inoculation in deep muscles" is relevant to how the virus gains access to nerve endings (proximity to NMJ).

For this exam question, the intended answer based on the listed options appears to be the mechanism related to retrograde neural spread, with "absence of early immune response" explaining the outcome.

Q49. A 45-year-old woman with hypopigmented patches on her back and loss of sensation over the patches for months. Suspected leprosy. Most appropriate initial investigation?

Blood culture
Skin biopsy culture
Detection of antibody
Acid-fast staining of skin scraping ✓

Answer: Acid-fast staining of skin scraping (Slit-skin smear)

Explanation:

Leprosy (Hansen's Disease) caused by Mycobacterium leprae:

Gram-positive, obligate intracellular
Acid-fast bacillus (AFB) - contains mycolic acids in cell wall
Cannot be cultured in standard laboratory media (footpad of armadillo/mice only)
Extremely slow replication (12-14 days doubling time - slowest of all bacteria)

Slit-skin smear (SSS) with Ziehl-Neelsen (acid-fast) stain:

Technique:

Small cut made in skin at 6 sites (earlobes ×2, lesion edges ×4)
Tissue fluid and cells collected
Spread on glass slide → stained with ZN stain
M. leprae = red acid-fast bacilli (retain carbol fuchsin after acid-alcohol decolorization)
Bacteria quantified as Bacterial Index (BI) (0 to 6+ scale) and Morphological Index (MI)

Leprosy classification:

Type	BI	Skin finding	Nerve
Tuberculoid (TT)	Negative (paucibacillary)	Few hypopigmented anesthetic patches	Asymmetric, thickened
Lepromatous (LL)	High positive (multibacillary)	Multiple, symmetric lesions, nodules	Diffuse

This patient: Hypopigmented patches with loss of sensation = tuberculoid or borderline leprosy presentation

Why SSS is first-line:

Simple, cheap, quick, non-invasive
Directly demonstrates the causative organism
Available in field/primary health settings
Quantifies bacterial load (guides treatment)

Why not others?

Blood culture: M. leprae doesn't grow in culture
Skin biopsy culture: M. leprae cannot be cultured conventionally; skin biopsy for histology is useful but not "culture"
Antibody detection (anti-PGL-1 IgM): useful for lepromatous type but poor sensitivity for tuberculoid (paucibacillary) leprosy

WHO treatment: Multi-drug therapy (MDT) - rifampicin + dapsone (PB) or rifampicin + dapsone + clofazimine (MB) for 6-12 months

Q50. A 58-year-old hypertensive patient given high-dose IV gentamicin develops hematuria progressing to anuric renal insufficiency. Mechanism of nephrotoxicity?

Tubular-cell toxicity ✓
Drug-induced crystal nephropathy
Altered intrarenal haemodynamics
Thrombotic microangiopathy

Answer: Tubular-cell toxicity (Proximal tubule toxicity)

Explanation:

Gentamicin nephrotoxicity mechanism:

Gentamicin is an aminoglycoside antibiotic - the most nephrotoxic antibiotic class.

Gentamicin filtered by glomerulus
         ↓
Cationic drug binds to anionic phospholipids of PROXIMAL TUBULE BRUSH BORDER
         ↓
Uptake by endocytosis via megalin/cubilin receptors
         ↓
Accumulates in LYSOSOMES of proximal tubule cells
         ↓
Lysosomal phospholipidosis → lysosomal membrane rupture
         ↓
Release of proteases → mitochondrial dysfunction
         ↓
ATP depletion → cell necrosis → ACUTE TUBULAR NECROSIS (ATN)
         ↓
Anuric renal failure

Risk factors for gentamicin nephrotoxicity:

High dose
Prolonged use (>7 days)
Pre-existing renal disease (hypertension in this patient → CKD risk)
Volume depletion
Concurrent nephrotoxins (NSAIDs, contrast, vancomycin)
Elderly, liver disease

Key features of aminoglycoside-induced ATN:

Proximal tubule cells (segment S1, S2) most affected
Non-oliguric ARF initially, progressing to oliguria/anuria
Hematuria (tubular damage)
Urinalysis: granular (muddy brown) casts, renal tubular epithelial cells
Typically occurs after 5-10 days of therapy
Usually reversible with drug cessation (unlike other ATN)

Other aminoglycoside toxicities:

Ototoxicity: cochlear (hearing loss - irreversible) and vestibular (vertigo, nystagmus)
Neuromuscular blockade (with anesthetics)

Why not others?

Crystal nephropathy: sulfonamides, acyclovir, methotrexate - NOT aminoglycosides
Altered haemodynamics: NSAIDs, ACE inhibitors, contrast agents
TMA: calcineurin inhibitors (cyclosporine, tacrolimus), quinine, some chemotherapy agents

Q51. A 35-year-old woman with known cholelithiasis presenting with epigastric pain and fever for 3 days, suspected acute cholecystitis. Most suggestive physical finding?

Abdominal rigidity
Epigastric tenderness
Murphy's sign ✓
Jaundice

Answer: Murphy's sign

Explanation:

Murphy's sign is the pathognomonic sign of acute cholecystitis:

Technique:

Patient breathes out fully
Examiner places fingers under the right costal margin at the midclavicular line (over gallbladder)
Patient takes a deep breath in
Positive = sudden inspiratory arrest/gasp due to pain as inflamed gallbladder descends onto examiner's fingers

Why Murphy's sign is specific for acute cholecystitis:

Inflamed gallbladder descends with inspiration → contacts examiner's fingers → sharp pain → reflex inspiratory arrest
Sensitivity ~65%, Specificity ~87% for acute cholecystitis
Absent in empyema or gangrenous cholecystitis (pain nerves may be destroyed)

Comparison of findings:

Finding	Specificity	Significance
Murphy's sign	Highly specific for acute cholecystitis	Pathognomonic
Epigastric tenderness	Non-specific	Many causes
Abdominal rigidity	Non-specific, suggests peritonitis	Complication
Jaundice	NOT typical	Suggests CBD obstruction (complication) or Mirizzi syndrome

Acute cholecystitis diagnosis (Tokyo Guidelines):

Murphy's sign + RUQ tenderness = clinical diagnosis
Ultrasound: gallstones, gallbladder wall thickening (>3mm), pericholecystic fluid, sonographic Murphy's sign
Lab: leukocytosis, elevated CRP, mild ALT/AST elevation

Q52. A patient with dyspnea, blood dyscrasias, history of sulfamethoxazole for bacillary dysentery for 2 weeks. Most likely cause?

Complications of infection
Poor iron absorption due to IBD
Sulpha drug-induced anemia ✓
Delayed recovery from infection

Answer: Sulpha drug-induced anemia (Hemolytic anemia)

Explanation:

Sulfamethoxazole (sulfonamide) causes hemolytic anemia, particularly in patients with G6PD (Glucose-6-Phosphate Dehydrogenase) deficiency.

Mechanism:

Sulfamethoxazole = OXIDANT DRUG
         ↓
Generates reactive oxygen species (H2O2, superoxide)
         ↓
In NORMAL RBCs: G6PD → NADPH → Glutathione → neutralizes oxidants
         ↓
In G6PD-DEFICIENT RBCs: NADPH depleted → glutathione depleted
         ↓
Oxidative stress → Hemoglobin oxidation → HEINZ BODIES (precipitated Hb)
         ↓
RBCs become rigid → trapped in spleen → EXTRAVASCULAR HEMOLYSIS
         ↓
Hemolytic anemia → dyspnea (anemia) + blood dyscrasias

Other sulfonamide adverse effects:

Effect	Mechanism
Hemolytic anemia	G6PD deficiency + oxidative damage
Stevens-Johnson Syndrome (SJS)	Severe hypersensitivity
Crystalluria/nephrolithiasis	Drug precipitation in acidic urine
Kernicterus (neonates)	Displaces bilirubin from albumin
Agranulocytosis	Immune-mediated
Folate deficiency anemia	Inhibits DHFR (especially in combination with trimethoprim)

G6PD deficiency facts:

X-linked recessive (affects males predominantly)
Most common enzyme deficiency in humans (~400 million affected)
Common in malaria-endemic areas (Africa, Mediterranean, Middle East, South/Southeast Asia)
Triggers: sulfonamides, dapsone, primaquine, nitrofurantoin, fava beans, infection

Blood dyscrasias in this context = hemolytic anemia (low Hb, elevated reticulocytes, elevated LDH, decreased haptoglobin, positive Coombs test in immune-mediated forms)

Q53. A 44-year-old man with abdominal pain and bloody diarrhea. Stool shows leukocytes, erythrocytes, and spiral/girdle-shaped bacteria. Campylobacter jejuni diagnosed. Most significant virulence factor causing inflammation?

Cytolethal distending toxin
Capsular polysaccharide
Adhesins ✓
Flagellins

Answer: Adhesins

Explanation:

Campylobacter jejuni virulence factors and their roles:

Virulence Factor	Role
Adhesins (CadF, FlpA, JlpA)	Initial attachment to intestinal epithelial cells - REQUIRED for all subsequent pathogenic events
Flagella (FlaA, FlaB)	Motility + invasion + immune evasion (T3SS-like)
Cytolethal Distending Toxin (CDT)	DNA double-strand breaks → G2/M cell cycle arrest → apoptosis
LPS/LOS	Endotoxin activity + molecular mimicry (Guillain-Barré syndrome)
CiaB protein	Secreted into host cells via flagellar T3SS → invasion

Why adhesins are most significant for INFLAMMATION:

The sequence of C. jejuni pathogenesis:

1. ADHESINS → attach to jejunal/ileal/colonic epithelium
              ↓
2. Flagella-mediated INVASION into epithelial cells
              ↓
3. CDT → epithelial cell damage
              ↓
4. Neutrophil and monocyte recruitment → INFLAMMATION
              ↓
5. Mucosal ulceration → BLOODY DIARRHEA

Without adhesion (step 1), no subsequent steps can occur. Adhesins (particularly CadF - Campylobacter Adhesin to Fibronectin) bind fibronectin on epithelial cells, initiating the entire inflammatory cascade. This makes adhesins the most fundamental/significant virulence factor for causing the intestinal inflammation in campylobacteriosis.

Campylobacter morphology: Comma-shaped, spiral/girdle-shaped (as in the question), motile, Gram-negative, microaerophilic (requires reduced O2/CO2 for growth), oxidase positive

Post-infectious complications of C. jejuni:

Guillain-Barré Syndrome (ascending flaccid paralysis) - molecular mimicry between LOS and gangliosides (GM1, GD1b) in peripheral nerve myelin
Reactive arthritis
Hemolytic uremic syndrome (rarely)

Q54. "Disease is an outcome of host-pathogen interaction wherein pathogens express a wide range of virulence." Which statement best describes virulence?

Ability to cause severe disease
Ability to evoke an immune response
Ability to cause death
Ability to cause clinical disease ✓

Answer: Ability to cause clinical disease

Explanation:

Key microbiology definitions:

Term	Definition
Virulence	Quantitative measure of pathogenicity - the relative ability of an organism to cause disease in a susceptible host
Pathogenicity	Qualitative ability to cause disease (yes/no)
Infectivity	Ability to establish infection in a host
Invasiveness	Ability to spread through tissues
Toxigenicity	Ability to produce toxins
Lethality	Ability to cause death
Virulence factor	A molecular trait that contributes to the organism's ability to cause disease

"Wide range of virulence" = spectrum from:

Subclinical/asymptomatic infection (low virulence)
Mild disease
Moderate clinical disease
Severe disease
Death (high virulence)

Why "ability to cause clinical disease" is the best answer:

Virulence = the degree to which a pathogen causes clinically apparent disease
"Ability to cause severe disease" = severity of virulence (not the definition itself)
"Ability to cause death" = lethality (extreme end of virulence spectrum)
"Ability to evoke immune response" = immunogenicity (separate concept - even harmless antigens evoke immune responses)

Virulence is measured by:

LD50 (lethal dose for 50% of hosts) - lower LD50 = more virulent
ID50 (infectious dose for 50% of hosts) - lower ID50 = more infective

Example: Mycobacterium tuberculosis has high virulence (causes clinical disease in ~10% of infected people) but low lethality in immunocompetent hosts (most cases are latent/controlled).

Q55. During a food poisoning outbreak, a medical officer investigates association between fried rice and food poisoning. P-value = 0.4. What conclusion?

Those who did not eat fried rice had food poisoning
Fried rice was associated with food poisoning
The rate of food poisoning is 40%
No association between taking fried rice and food poisoning ✓

Answer: No association between taking fried rice and food poisoning (fail to reject null hypothesis)

Explanation:

P-value interpretation:

P-value	Interpretation
p < 0.05	Statistically significant - reject null hypothesis, evidence of association
p ≥ 0.05	Not statistically significant - fail to reject null hypothesis, insufficient evidence
p = 0.4	Well above 0.05 - clearly NOT significant

In this case, p = 0.4 means:

If there were truly NO association between fried rice and food poisoning (null hypothesis true), there is a 40% probability of observing results as extreme as those found purely by chance
Since p = 0.4 >> 0.05 (significance threshold), we FAIL TO REJECT the null hypothesis
Conclusion: No statistically significant association between fried rice consumption and food poisoning

Common misconceptions about p-values:

p = 0.4 does NOT mean "40% chance of food poisoning"
p = 0.4 does NOT prove the null hypothesis is true (absence of evidence ≠ evidence of absence)
p = 0.4 does NOT mean there is definitely no association - only that the sample did not provide sufficient evidence

Statistical significance vs clinical significance:

A result can be statistically significant but clinically irrelevant (especially in large sample sizes)
A result can be clinically important but not statistically significant (small sample size, type II error)

Q56. A 45-year-old patient with Cryptococcus neoformans meningitis started on amphotericin B + flucytosine combination. Best explanation for combination?

It reduces the side effects
It prevents resistance to antifungal agents ✓
It enhances spectrum of antifungal activity
It improves the penetration of drug into CNS

Answer: Prevents resistance to antifungal agents (+ synergistic effect)

Explanation:

Cryptococcal meningitis treatment protocol (WHO/IDSA):

Phase	Duration	Regimen
Induction	2 weeks	Amphotericin B deoxycholate + Flucytosine (5-FC)
Consolidation	8 weeks	Fluconazole 400mg/day
Maintenance	≥1 year	Fluconazole 200mg/day

Rationale for combination (Ampho B + 5-FC):

1. Synergistic effect:

Amphotericin B → binds ergosterol → pores in fungal membrane
         ↓
Increased membrane permeability
         ↓
Enhanced intracellular uptake of 5-FC
         ↓
5-FC converted to 5-fluorouracil (5-FU) by fungal cytosine deaminase
         ↓
5-FU → inhibits thymidylate synthase → disrupts DNA/RNA synthesis
         ↓
COMBINED FUNGICIDAL EFFECT > either drug alone

2. Prevention of resistance:

5-FC monotherapy rapidly selects for resistant mutants (mutations in cytosine deaminase or permease = resistance rate ~40% if used alone)
Combining with Ampho B prevents emergence of 5-FC resistance
Faster CSF sterilization = better outcomes

3. Both drugs have good CNS penetration:

Ampho B: lipid formulations penetrate BBB
5-FC: excellent CNS penetration (small, hydrophilic molecule, CSF/serum ratio ~70-80%)

Why not "reduces side effects"?

Actually the combination has MORE side effects (additive nephrotoxicity from Ampho B + myelosuppression from 5-FC) - this option is incorrect

Why not "enhances spectrum"?

Both drugs target Cryptococcus - the spectrum is not expanded, just efficacy enhanced

Q57. A 35-year-old man with fever and inguinal lymphadenopathy diagnosed with filariasis. Drug of choice?

Pyrantel pamoate
Albendazole
Diethylcarbamazine (DEC) ✓
Praziquantel

Answer: Diethylcarbamazine (DEC)

Explanation:

Lymphatic filariasis caused by:

Wuchereria bancrofti (most common, ~90%)
Brugia malayi and B. timori
Transmitted by mosquitoes (Culex, Anopheles, Aedes)
Microfilariae circulate in blood (nocturnal periodicity for W. bancrofti)
Adult worms in lymphatics → lymphatic obstruction → lymphedema
Inguinal lymphadenopathy (as in this patient) is a classic feature

Treatment of filariasis:

Drug	Role	Notes
Diethylcarbamazine (DEC)	Drug of choice - kills both microfilariae AND adult worms	First-line for individual treatment and MDA programs
Ivermectin	Kills microfilariae only	Used in combination in MDA
Albendazole	Kills adult worms (slow)	Used in combination in MDA
DEC + albendazole	MDA (Mass Drug Administration)	WHO program for elimination
DEC + albendazole + ivermectin	Triple drug MDA	Most effective MDA regimen

DEC mechanism:

Immobilizes microfilariae (reduces motility) → enhanced phagocytosis
Direct filaricidal effect against adult worms
Alters surface antigens of microfilariae → immune-mediated killing

Why not others?

Praziquantel: used for trematodes (schistosomiasis, liver flukes, lung flukes) and cestodes (tapeworms) - NOT nematodes/filariae
Pyrantel pamoate: treats intestinal nematodes (roundworm, hookworm, pinworm) - NOT filariae
Albendazole: broad-spectrum antihelminthic, used as adjunct in filariasis but NOT drug of choice alone

Q58. A 31-year-old woman with whitish vaginal discharge and dyspareunia. Confirmed chronic cervicitis. Major diagnostic indicator?

Reactive atypia of the endocervical epithelium
Oedema of the subepithelial matrix
Haemorrhage of the submucosal region
Mononuclear cells infiltrate in squamo-columnar junction ✓

Answer: Mononuclear cell infiltrate at the squamo-columnar junction

Explanation:

Chronic cervicitis histology:

Normal cervix: The squamo-columnar junction (SCJ) or transformation zone is where stratified squamous epithelium (ectocervix) meets columnar glandular epithelium (endocervix). This zone is biologically active and vulnerable to infection/metaplasia.

Chronic cervicitis histological features:

Feature	Significance
Mononuclear cell infiltrate (lymphocytes, plasma cells, macrophages)	HALLMARK of chronic inflammation - distinguishes chronic from acute
Concentrated at squamo-columnar junction	Most biologically active, vulnerable zone
Lymphoid follicles (sometimes)	Reactive germinal centers (especially in chlamydial cervicitis)
Squamous metaplasia	Replacement of columnar by squamous epithelium (protective)
Reactive atypia of epithelium	Secondary change, not primary feature

Why mononuclear infiltrate is the MAJOR diagnostic indicator:

The presence of lymphocytes and plasma cells (mononuclear cells) = chronic inflammation = chronic cervicitis
This is the defining histopathological criterion for chronic cervicitis
Concentrated at the SCJ because this is where most cervical pathogens (C. trachomatis, HPV, HSV) preferentially infect

Why not others?

Reactive atypia: secondary, non-specific feature; does not define the diagnosis
Oedema: feature of acute cervicitis (early exudative phase)
Haemorrhage: feature of acute cervicitis, not chronic

Common causes of chronic cervicitis: Chlamydia trachomatis (most common STI cause), HPV, Trichomonas, bacterial vaginosis organisms, Herpes

Q59. A 52-year-old man with watery diarrhea and abdominal bloating. Stool shows pear-shaped, flagellated, motile organisms. Most likely cause?

Entamoeba histolytica
Giardia lamblia ✓
Entamoeba coli
Balantidium coli

Answer: Giardia lamblia (Giardia intestinalis/duodenalis)

Explanation:

Pear-shaped + flagellated + motile = Giardia lamblia - this is a textbook identification.

Giardia morphology:

Stage	Shape	Features
Trophozoite	Pear/teardrop-shaped	2 nuclei ("owl face"), 4 pairs of flagella, sucking disc (adhesion organelle), bilateral symmetry, "falling leaf" motility
Cyst	Oval	4 nuclei, 4 median bodies, infective stage

Clinical features of giardiasis:

Watery, foul-smelling, frothy, greasy diarrhea (steatorrhea - fat malabsorption)
Abdominal bloating, flatulence - as in this patient
Nausea, belching (sulfurous "rotten egg" burps)
NO blood, NO mucus (non-invasive - stays in lumen of duodenum/jejunum)
Chronic infection → weight loss, malabsorption, lactose intolerance
Common in travelers (traveler's diarrhea), children in daycare, immunocompromised (especially IgA deficiency, hypogammaglobulinemia)

Differentiation from Entamoeba histolytica:

Feature	Giardia lamblia	Entamoeba histolytica
Diarrhea	Watery, greasy, frothy	Bloody, mucoid (dysentery)
Invasion	Non-invasive	Invasive (penetrates colonic mucosa)
Shape	Pear-shaped trophozoite	Rounded trophozoite with ingested RBCs
Location	Duodenum/jejunum	Colon
Extra-intestinal	Rare	Common (liver abscess)
Cyst	4-nucleated oval	4-nucleated rounded (chromatoid bodies)

Diagnosis: Stool microscopy (trophozoites or cysts), ELISA (stool antigen - most sensitive), PCR, duodenal aspirate/string test

Treatment: Metronidazole 250mg TID for 5-7 days (drug of choice); alternatives: tinidazole (single dose), nitazoxanide

Q60. A 63-year-old obese, hypertensive woman with post-menopausal vaginal bleeding for 3 days. Menopause at 54. Normal-sized uterus. Endometrial biopsy shows neoplastic lesion of epithelial origin. Most likely type?

Squamous cell carcinoma
Adenocarcinoma ✓
Choriocarcinoma
Leiomyosarcoma

Answer: Adenocarcinoma (Endometrial adenocarcinoma)

Explanation:

Post-menopausal bleeding = endometrial carcinoma until proven otherwise.

Type I Endometrial Carcinoma (Endometrioid adenocarcinoma):

Risk factors present in this patient:

Obesity - adipose tissue converts androgens to estrone (estrogen) via aromatase → excess unopposed estrogen → endometrial hyperplasia → carcinoma
Hypertension - associated with metabolic syndrome
Post-menopausal - increasing age
Late menopause (54 years) = prolonged estrogen exposure

EPIC mnemonic for Type I endometrial cancer risk factors:

Exogenous estrogen (unopposed)
Polycystic ovary syndrome (PCOS)
Infertility / Anovulation
Chronic disease (obesity, DM, HTN)
Nulliparity, Late menopause, Early menarche

Endometrial carcinoma types:

Type	Histology	Estrogen	Prognosis
Type I (~80%)	Endometrioid adenocarcinoma	Estrogen-dependent	Better
Type II (~20%)	Serous or clear cell carcinoma	Estrogen-independent	Worse

Why adenocarcinoma:

"Neoplastic lesion of epithelial origin" = carcinoma (arising from glandular epithelium = adenocarcinoma)
Endometrium is glandular mucosa → malignancy = adenocarcinoma
Most common gynecological malignancy in developed countries

Why not others?

Squamous cell carcinoma: extremely rare in endometrium (endometrium has glandular, not squamous epithelium)
Choriocarcinoma: from trophoblastic cells, associated with gestational trophoblastic disease, elevated β-hCG, most common in young women post-pregnancy (not post-menopausal with normal uterus)
Leiomyosarcoma: mesenchymal (smooth muscle) origin = NOT epithelial. Rare, presents as a large uterine mass, not amenable to endometrial biopsy diagnosis typically

Investigations:

Transvaginal ultrasound: endometrial stripe >4mm post-menopause = abnormal
Endometrial biopsy (as done here) = diagnostic
D&C (dilatation and curettage) if biopsy inadequate

Treatment: Total abdominal hysterectomy + bilateral salpingo-oophorectomy (TAH-BSO) ± radiotherapy

Summary Table - Q35 to Q60

Q	Answer	Core Concept
35	Mumps vaccine (MMR - live)	Live vaccines contraindicated in immunocompromised
36	Lipodystrophy	Repeated injection → lipohypertrophy → erratic absorption
37	Parathyroid adenoma	Single gland uptake on sestamibi = adenoma (85% of primary HPT)
38	Somnolence	Gabapentin's most common side effect; nystagmus = phenytoin
39	Testicular torsion	Surgical emergency; salvage depends on time (<6h = ~100%)
40	Trastuzumab	HER2+ → monoclonal antibody; tamoxifen = ER+ only
41	Mask visceral pain	Classical teaching (modern evidence supports analgesia, but exam answer = masking)
42	Anthropometry	Direct, quantitative, objective nutritional assessment
43	Selectively antagonises oestrogen receptor	Clomiphene blocks hypothalamic ER → removes negative feedback → ↑FSH
44	Protein 24 (p24)	Earliest antigen in HIV; 4th gen test detects p24 + antibodies
45	Superficial columnar and goblet cells	Peutz-Jeghers = hamartoma with arborizing smooth muscle + normal epithelium
46	Gastric acid	Basal hyperplasia + papillae elongation + eosinophils = GERD histology
47	Papillary urothelial carcinoma	Bladder TCC = 90% of bladder cancers
48	Retrograde axonal transport / absence of immune response	Rabies: axonal highway to CNS; inside axons = immune evasion
49	Acid-fast staining skin scraping	M. leprae cannot be cultured; SSS = standard field test
50	Tubular-cell toxicity	Aminoglycosides → proximal tubule → ATN via lysosomal damage
51	Murphy's sign	Pathognomonic of acute cholecystitis; inspiratory arrest on RUQ palpation
52	Sulpha drug-induced anemia	Sulfonamides + G6PD deficiency → oxidative hemolytic anemia
53	Adhesins	C. jejuni: adhesins initiate epithelial attachment → entire inflammatory cascade
54	Ability to cause clinical disease	Virulence = quantitative degree of pathogenicity
55	No association (p = 0.4 > 0.05)	Fail to reject null hypothesis; p ≠ rate/percentage
56	Prevents resistance	5-FC alone → rapid resistance; Ampho B prevents this + synergy
57	Diethylcarbamazine (DEC)	Drug of choice for lymphatic filariasis; praziquantel = trematodes/cestodes
58	Mononuclear cell infiltrate at SCJ	Hallmark of chronic inflammation = lymphocytes/plasma cells
59	Giardia lamblia	Pear-shaped + flagellated + watery diarrhea = Giardia
60	Adenocarcinoma	Post-menopausal bleeding + epithelial origin + obesity = endometrial adenocarcinoma

61. A 50-year-old diabetic male presents with dysphagia for the past 3 months. He is a chronic smoker. Upper Gl endoscopy and biopsy reveals adenocarcinoma located in the lower end of esophagus. Adjacent area shows features of intestinal metaplasia. Which of the following is the most significant predisposing factor for the above condition in this patient? A. Chemical esophagitis B. Eosinophilic esophagitis C. Infectious esophagitis D. Reflux oesophagitis 62. A 56-year-old male presents with history of recurrent epigastric pain associated with nausea in the past three months. An upper Gl endoscopy reveals a punched-out ulcer in the gastric antrum. Biopsy from the ulcer reveals presence of H.pylori. Which of the following factors is the most likely cause of the above condition? A. Increased gastrin production B. Increased pepsin production C. Reduced epithelial regeneration D. Reduced gastroprotective prostaglandins 63. A 7-month-old infant is brought to the Emergency Department with a six-hour history of vomiting, inconsolable crying and drawing up of the legs toward the abdomen. He has a history of viral gastroenteritis. A clinical diagnosis of intestinal obstruction is made. Radiologic studies reveal the invagination of a part of the intestine to a distal segment. Which of the following conditions is the most likely aetiology of intestinal obstruction in this child? A. Adhesions B. Hernia C. Intussusception D. Volvulus 64. A 56-year-old man has been discharged from the ward after recovering from acute pancreatitis. Two weeks later, he presented with abdominal mass and obstructive jaundice. Which of the following complications is most likely to occur in this patient? A. Chronic pancreatitis B. Pancreatic carcinoma C. Pancreatic pseudocyst D. Recurrent acute pancreatitis 65. A 35-year-old man presents to the Emergency Department with fever, headache,altered bowel habits for a week. On examination, hydration is fair, temperature 40°C, pulse rate 80/minute. There is hepatosplenomegaly and rose spots are observed on his back. Based on the laboratory investigations, a diagnosis of typhoid fever is made. Which of the following describes the characteristic of the causative organism? A. Gram-positive bacillus B. Obligate anaerobe C. Non-motile D. Non-lactose fermenter 66. A 15-year-old girl presents to the clinic with diarrhoea and stomach cramps for two days. She had consumed half-boiled eggs before the symptoms appeared. Stool culture grows non-lactose fermenters on MacConkey agar. A diagnosis of food poisoning is made. Which of the following organisms is most likely to cause these symptoms in this patient? A. Helicobacter Pylori B. Salmonella typhimurium C. Staphylococcus aureus D. Vibrio cholera 67. A 50-year-old man presents to an Outpatient Clinic with bloody diarrhoea. On physical examination, ascites and hepatomegaly is detected. Stool examination reveals large-sized eggs that have lateral spines. Which of the following complications is most likely to occur in this patient due to the above parasitic infection? A. Cercarial dermatitis B. Haematemesis C. Hematuria D. Verminous pneumonitis 68. A 35-year-old woman presents to the clinic with diarrhoea, itching and irritation in the perianal area. Stool examination reveals Tania saginata eggs and segments. Which of the following is the most likely intermediate host for this parasite? A. Cattle B. Freshwater Fish C. Pig D. Shrimp 69. A 12-year-old boy presents to the Outpatient Clinic with abdominal pain and diarrhoea. Stool examination reveals an egg with a characteristic mammillated outer shell. The boy is diagnosed with ascariasis and given treatment. Few days later, he presented to Emergency Department with an acute abdomen. Which of the following conditions is the most likely complication of the above parasitic infection? A. Cholangitis B. Cholecystitis C. Intestinal Obstruction D. Intestinal perforation 70. A 35-year-old man presents to the clinic with fever, abdominal pain and diarrhoea for two days. On examination, temperature is 38.5°C. Other vital signs are normal. Lower quadrant abdominal tenderness is observed. Based on the stool microscopic examination, a diagnosis of intestinal amoebiasis is made. Which of the following findings is most significant in the identification of the causative agent in this case? A. Ingested red blood cells B. Mass of glycogen C. Pseudopodia D. Spherical nucleus with central karyosome 71. A 49-year-old man recently diagnosed with colonic adenocarcinoma undergoes radiation therapy which is later followed by chemotherapy. A drug that acts on 5 - HT2 receptors is prescribed to the patient to relieve nausea and vomiting induced by chemotherapeutic agents. Which of the following drugs is most likely prescribed to this patient to prevent the above side effects? A. Diphenhydramine B. Ondansetron C. Phenothiazine D. Scopolamine 72. A 45-year-old man presents to the clinic with epigastric pain. The physician prescribes famotidine. Which of the following mechanisms of action best describes the above drug? A. It blocks histamine receptors. B. It blocks the proton pump. C. It neutralizes gastric acid. D. It promotes mucosa production. 73. A 23-year-old man presents to the clinic with rice watery diarrhea. He gave history of street food intake two days back. He is suspected of cholera. Which of the following therapies is most likely contraindicated in this patient? A. Antimicrobial therapy B. Antimotility therapy C. Antisecretory therapy D. Fluid replacement therapy 74. A 52-year-old man presents to the clinic with unilateral leg swelling. After physical examination and investigations, he is diagnosed with filariasis Which of the following antiparasitic drugs is most likely indicated for this patient? A. Albendazole B. Diethylcarbamazine C. Ivermectin D. Pyrantel pamoate 75. A 9-year-old boy presents with a recent onset of oliguria and cola-coloured smoky urine after recovering from an episode of sore throat. Physical examination shows presence of periorbital e d e m a and hypertension. Laboratory investigations reveal elevated serum urea and creatinine. Which of the following findings is most likely to be seen in the microscopic urinary examination of this child? A. Eosinophilic casts B. Muddy brown casts C. RBC casts D. WBC casts 76. A 3-year-old boy is brought to the clinic because of irritability and reddish-coloured urine for the last few days. Abdominal CT scan detects a 3.1 cm mass arising from the right kidney. A histological section from the surgically excised mass reveals a triphasic malignant neoplasm, made with neoplastic blastemal, stromal, and epithelial tissues. Which of the following renal neoplasms best fits the above description? A. Clear cell renal cell carcinoma B. Papillary renal cell carcinoma C. Rhabdoid tumour of kidney D. Wilms tumour 77. A 35-year-old man is brought to the Emergency Department with hypovolemic shock due to road traffic accident. He develops oliguria. Blood investigations show elevated serum urea and creatinine. Urine examination reveals the presence of granular cast Which of the following disorders is most likely to be present in this patient? A. Acute papillary necrosis B. Acute tubular necrosis C. Prerenal azotemia D. Tubulointerstitial nephritis 78. A 32-year-old woman presents to the hospital with complaints of dysuria and clear urethral discharge for the past ten days. Diagnosis of non-gonococcal urethritis is made and Chlamydia trachomatis is detected in the urethral specimen. Which of the following diagnostic tests is most suitable for serovar confirmation of this causative organism? A. Complement fixation test B. Culture on McCoy cells C. Direct fluorescent antibody test D. Microimmunofluorescence test 79. A 25-year-old woman is admitted to the hospital with three days history of high-grade fever, chills, rigours and flank pain. Based on laboratory investigations, which include urine analysis, a diagnosis of acute pyelonephritis is made Which of the following findings is expected in this patient's urine analysis? A. Bacterial count 1,000 cells per ml. B. High glucose level C. High red blood cell count. D. Presence of white blood cells cast 80. A 37-year-old woman presents to the Emergency Department with severe right flank pain and haematuria. Following investigations, she is diagnosed with renal calcium oxalate stones. She is later discharged with a diuretic to prevent future stones formation. Which of the following diuretics is most likely prescribed to this patient? A. Ethacrynic acid B. Furosemide C. Hydrochlorothiazide D. Spironolactone

Here are all 20 questions (Q61-Q80) answered fully:

Q61. A 50-year-old diabetic, chronic smoker with dysphagia for 3 months. Endoscopy shows adenocarcinoma at the LOWER END of esophagus with adjacent intestinal metaplasia. Most significant predisposing factor?

Chemical esophagitis
Eosinophilic esophagitis
Infectious esophagitis
Reflux esophagitis ✓

Answer: Reflux esophagitis (GERD → Barrett's esophagus → Adenocarcinoma)

Explanation:

The critical clue: "Adenocarcinoma at LOWER END of esophagus + adjacent intestinal metaplasia"

This is the classic sequence of Barrett's esophagus → esophageal adenocarcinoma:

Chronic GERD (reflux esophagitis)
           ↓
Repeated acid/bile exposure to distal esophageal mucosa
           ↓
Squamous epithelium replaced by INTESTINAL METAPLASIA
(columnar epithelium with goblet cells = Barrett's esophagus)
           ↓
Low-grade dysplasia → High-grade dysplasia
           ↓
ADENOCARCINOMA (lower third of esophagus / GEJ)

Barrett's esophagus:

Metaplastic replacement of normal stratified squamous epithelium by specialized intestinal metaplasia (columnar epithelium with goblet cells)
Develops in distal/lower esophagus (acid exposure site)
Premalignant condition - risk of adenocarcinoma ~0.1-0.5% per year
Diagnosed endoscopically + confirmed by biopsy showing goblet cells (the "intestinal metaplasia" mentioned in this question)

Risk factors for Barrett's/Adenocarcinoma:

Chronic GERD (most important - present in this patient as diabetic with likely gastroparesis + smoking reducing LES tone)
Obesity (increased abdominal pressure)
Smoking (reduces LES pressure, impairs mucosal defense)
Male sex
White race
Age >50

Esophageal cancer types - location distinction:

Feature	Adenocarcinoma	Squamous Cell Carcinoma
Location	Lower third / GEJ	Upper/middle third
Precursor	Barrett's (intestinal metaplasia)	Squamous dysplasia
Risk factors	GERD, obesity, Barrett's	Alcohol, smoking, hot beverages, achalasia
Incidence trend	Rising rapidly	Declining

Why not others?

Chemical esophagitis (caustic ingestion) → SCC of upper/middle esophagus
Eosinophilic esophagitis → dysphagia in young males, no malignant transformation
Infectious esophagitis (Candida/HSV) → in immunocompromised, no malignant transformation

Q62. A 56-year-old man with recurrent epigastric pain and nausea. Gastric antral ulcer with H. pylori on biopsy. Most likely cause of the ulcer?

Increased gastrin production
Increased pepsin production
Reduced epithelial regeneration
Reduced gastroprotective prostaglandins ✓

Answer: Reduced gastroprotective prostaglandins

Explanation:

H. pylori pathogenesis of peptic ulcer:

H. pylori virulence factors:

Urease: splits urea → NH3 → neutralizes local acid → allows bacterial survival → NH3 directly toxic to mucosa
CagA protein (cytotoxin-associated gene A): virulence factor injected into epithelial cells → promotes inflammation, disrupts cell junctions
VacA (vacuolating cytotoxin): forms vacuoles in epithelial cells → cell death
Phospholipases: degrade phospholipid layer of mucus → weakens mucus barrier
Proteases: break down mucus gel

How H. pylori reduces gastroprotective prostaglandins:

H. pylori infection → epithelial damage + inflammatory response
           ↓
Neutrophils and macrophages recruited
           ↓
COX-2 induced BUT H. pylori specifically DOWNREGULATES
gastroprotective prostaglandins (PGE2, PGI2) synthesis
           ↓
Loss of prostaglandin-mediated protection:
- ↓Mucus secretion
- ↓Bicarbonate secretion
- ↓Mucosal blood flow
- ↓Epithelial regeneration
           ↓
Mucosal barrier weakened → acid/pepsin access → ULCERATION

Gastric mucosal defense mechanisms:

Defense Layer	Component	H. pylori Effect
Pre-epithelial	Mucus + bicarbonate layer	Degraded by phospholipases + proteases
Epithelial	Tight junctions, rapid renewal	Disrupted by CagA, VacA
Post-epithelial	Mucosal blood flow (prostaglandin-mediated)	Reduced prostaglandins = reduced blood flow

Why "reduced gastroprotective prostaglandins" is the BEST answer:

Prostaglandins (PGE2, PGI2) are the master regulators of gastric mucosal defense
Their reduction is the central downstream mechanism by which H. pylori causes mucosal vulnerability
This is also the mechanism by which NSAIDs cause peptic ulcers (COX inhibition → ↓prostaglandins)
H. pylori + NSAIDs have synergistic ulcerogenic effect through this shared pathway

Treatment of H. pylori: Triple therapy - PPI + Amoxicillin + Clarithromycin (14 days), or bismuth quadruple therapy

Q63. A 7-month-old infant with vomiting, inconsolable crying, legs drawn up, history of viral gastroenteritis. Radiologic studies show invagination of intestine into a distal segment. Aetiology?

Adhesions
Hernia
Intussusception ✓
Volvulus

Answer: Intussusception

Explanation:

The question already describes intussusception - "invagination of a part of the intestine into a distal segment" IS the definition of intussusception.

Intussusception:

Most common cause of intestinal obstruction in infants 6-36 months (peak: 6-12 months)
One segment of bowel (intussusceptum) telescopes into the adjacent distal segment (intussuscipiens)
Most common location: ileocolic junction (terminal ileum invaginates into cecum/colon)

Classic clinical triad (present in only ~20% but highly specific):

Colicky abdominal pain (intermittent, severe, child draws up legs)
Vomiting (bilious later)
"Currant jelly" stools (blood + mucus from mucosal ischemia - late sign)

Additional features:

"Dance's sign": empty RLQ on palpation (cecum displaced)
Sausage-shaped mass palpable in RUQ
Lethargy (may look septic if late presentation)

Association with viral gastroenteritis:

Viral gastroenteritis (adenovirus, rotavirus) → hypertrophied Peyer's patches → act as a lead point for intussusception
This explains the history of viral gastroenteritis before onset

Imaging:

Ultrasound (first-line): "target sign" / "doughnut sign" (concentric rings on transverse view)
Plain X-ray: absent cecal gas, soft tissue mass
Contrast/air enema: "coiled spring sign" on barium; therapeutic as well

Treatment:

Non-surgical: air enema reduction (first-line, ~80% success if no peritonitis)
Surgical: laparotomy if enema fails, peritonitis, or lead point found

Differentiating causes of intestinal obstruction:

Cause	Age	Mechanism	Key Feature
Intussusception	6-36 months	Telescoping	History of gastroenteritis, currant jelly stools
Adhesions	Post-surgical	Fibrous bands	Previous surgery history
Hernia	Any age	External compression	Visible/palpable hernia
Volvulus	Neonates or elderly	Twisting	Midgut (neonate) or sigmoid (elderly)
Hirschsprung's	Neonate	No peristalsis (no ganglia)	Failure to pass meconium

Q64. A 56-year-old man recovering from acute pancreatitis presents 2 weeks later with abdominal mass and obstructive jaundice. Most likely complication?

Chronic pancreatitis
Pancreatic carcinoma
Pancreatic pseudocyst ✓
Recurrent acute pancreatitis

Answer: Pancreatic pseudocyst

Explanation:

Timeline is the key: 2 weeks after acute pancreatitis + abdominal mass

Pancreatic pseudocyst:

Collection of pancreatic secretions, necrotic debris, and inflammatory fluid enclosed by a fibrous wall (no true epithelial lining - hence "pseudo" cyst)
Develops 2-6 weeks after acute pancreatitis
Forms when pancreatic enzymes leak from disrupted ducts → accumulate → wall forms over time

Why obstructive jaundice:

A large pseudocyst in the head of pancreas region → extrinsic compression of the common bile duct → obstructive (post-hepatic) jaundice
Features: jaundice, pale stools, dark urine, elevated direct bilirubin, elevated ALP/GGT

Clinical features of pancreatic pseudocyst:

Persistent or recurrent abdominal pain after acute pancreatitis
Palpable epigastric/abdominal mass (as in this case)
Nausea, early satiety, weight loss
Elevated serum amylase/lipase (persistent)
Fever if infected (pancreatic abscess)

Diagnosis:

CT scan (gold standard): well-defined fluid collection adjacent to pancreas
Ultrasound (initial screening)
MRCP (magnetic resonance cholangiopancreatography): shows ductal disruption
EUS (endoscopic ultrasound): best for drainage planning

Treatment:

Small (<6cm, asymptomatic): conservative management - may resolve spontaneously (40-60%)
Large, symptomatic, or enlarging: drainage - endoscopic (EUS-guided cystogastrostomy), surgical, or percutaneous

Why not others?

Chronic pancreatitis: occurs over years of repeated injury, not 2 weeks
Pancreatic carcinoma: would not develop acutely 2 weeks after pancreatitis; though pancreatitis can be CAUSED by pancreatic cancer obstructing ducts
Recurrent acute pancreatitis: would present with pain/elevated enzymes, not a palpable mass

Q65. A 35-year-old man with fever (40°C), headache, altered bowel habits, hepatosplenomegaly, and rose spots on back. Diagnosed with typhoid fever. Characteristic of the causative organism?

Gram-positive bacillus
Obligate anaerobe
Non-motile
Non-lactose fermenter ✓

Answer: Non-lactose fermenter

Explanation:

Salmonella typhi (cause of typhoid fever) characteristics:

Property	Detail
Gram stain	Gram-NEGATIVE bacillus (not positive)
Oxygen requirement	Facultative anaerobe (not obligate anaerobe)
Motility	MOTILE (peritrichous flagella - H antigen) - so non-motile is wrong
Lactose fermentation	NON-LACTOSE FERMENTER → pale/colorless on MacConkey agar ✓
H2S production	Positive (produces black colonies on Hektoen/XLD agar)
Urease	Negative
Antigens	O (somatic LPS), H (flagellar), Vi (capsular - virulence/typhoidal)
Culture	Blood culture (1st week), urine/stool (2nd-3rd week)

Typhoid fever clinical features:

Week	Features
Week 1	Stepladder fever, headache, relative bradycardia, constipation (early)
Week 2	Rose spots (salmon-colored maculopapular rash on trunk = 2-4mm, blanching, 10-20 spots), hepatosplenomegaly, diarrhea
Week 3	Complications: intestinal perforation, hemorrhage, encephalopathy
Week 4	Resolution or complications

Rose spots: Caused by S. typhi emboli in dermal capillaries - present in ~30% of cases, best seen on fair-skinned individuals.

Widal test: Agglutination test detecting anti-O and anti-H antibodies (not highly sensitive/specific).

Diagnosis: Blood culture (gold standard, positive in >80% during 1st week).

Treatment: Ciprofloxacin or azithromycin (first-line); ceftriaxone for MDR strains.

Q66. A 15-year-old girl with diarrhea and stomach cramps after eating half-boiled eggs. Stool culture grows non-lactose fermenters on MacConkey. Diagnosis: food poisoning. Causative organism?

Helicobacter pylori
Salmonella typhimurium ✓
Staphylococcus aureus
Vibrio cholerae

Answer: Salmonella typhimurium (non-typhoidal Salmonella)

Explanation:

Key clues:

Half-boiled eggs → classic source of Salmonella (colonizes hen ovaries → egg contamination)
Non-lactose fermenter on MacConkey → Salmonella (colorless/pale colonies)
Diarrhea + cramps (gastroenteritis pattern)
Food poisoning diagnosis

Salmonella typhimurium (non-typhoidal Salmonella):

Gram-negative, non-lactose fermenter
Non-typhoidal Salmonella: S. typhimurium, S. enteritidis (cause gastroenteritis, NOT typhoid)
Sources: eggs, poultry, meat, dairy, reptiles
Incubation: 6-48 hours
Symptoms: diarrhea (may be bloody), abdominal cramps, nausea, vomiting, fever (~38-39°C)
Self-limiting in immunocompetent (3-7 days)
Antibiotic treatment only for severe/systemic disease (antibiotics may prolong carrier state)

Food poisoning comparison:

Organism	Food Source	Incubation	Key Feature
Salmonella spp.	Eggs, poultry	6-48h	Non-lactose fermenter, H2S positive
S. aureus	Cream, custard, potato salad	1-6h (preformed toxin)	Vomiting prominent, no fever, Gram-positive cocci
Vibrio cholerae	Contaminated water, seafood	2-3 days	Rice-water diarrhea, massive fluid loss
H. pylori	Not food poisoning per se	Chronic	Gastric ulcer, H pylori not a typical food poisoning agent
B. cereus	Fried rice (reheated)	1-6h (emetic) or 6-24h (diarrheal)	Two toxin syndromes

Why not Staphylococcus aureus?

S. aureus is Gram-positive → would NOT grow as non-lactose fermenter on MacConkey
S. aureus food poisoning: prominent vomiting, very short incubation (1-6h), caused by preformed heat-stable enterotoxin (toxin present in food even after cooking)

Q67. A 50-year-old man with bloody diarrhea, ascites, hepatomegaly. Stool shows large eggs with LATERAL SPINES. Most likely complication?

Cercarial dermatitis
Haematemesis ✓
Hematuria
Verminous pneumonitis

Answer: Haematemesis (from portal hypertension + esophageal varices)

Explanation:

Large eggs with LATERAL SPINES = Schistosoma mansoni (or S. japonicum - has smaller lateral spine)

Schistosoma species identification by egg morphology:

Species	Egg Spine	Location	Manifestation
S. mansoni	Lateral spine (large)	Mesenteric veins (inferior)	Intestinal + hepatic
S. haematobium	Terminal (end) spine	Vesical (bladder) plexus	Urinary - hematuria
S. japonicum	Small lateral spine	Mesenteric veins (superior)	Intestinal + hepatic (severe)

S. mansoni pathogenesis → Haematemesis:

Adult worms in mesenteric veins (portal tributaries)
           ↓
Eggs deposited → embolize to liver via portal vein
           ↓
Eggs trapped in portal tracts → GRANULOMATOUS INFLAMMATION
           ↓
Periovular granulomas (CD4+ T cell mediated) → FIBROSIS
           ↓
PERIPORTAL ("pipestem") FIBROSIS (Symmers' fibrosis)
           ↓
PORTAL HYPERTENSION (pre-sinusoidal/intrahepatic block)
           ↓
Esophageal varices + Ascites + Splenomegaly
           ↓
Variceal rupture → HAEMATEMESIS (vomiting blood)

This patient's findings explained:

Bloody diarrhea: intestinal schistosomiasis (eggs in bowel wall)
Hepatomegaly: hepatic granulomas + fibrosis
Ascites: portal hypertension → low oncotic pressure from liver dysfunction
Haematemesis: esophageal variceal bleeding (most dangerous complication)

Why not hematuria? That is S. haematobium (terminal spine). This patient has lateral-spined eggs = S. mansoni = intestinal/hepatic disease, not urinary.

Treatment: Praziquantel (drug of choice for ALL Schistosoma species)

Q68. A 35-year-old woman with diarrhea and perianal itching. Stool shows Taenia saginata eggs and segments. Most likely intermediate host?

Cattle ✓
Freshwater fish
Pig
Shrimp

Answer: Cattle (beef tapeworm)

Explanation:

Taenia species and their intermediate hosts:

Tapeworm	Common Name	Intermediate Host	Infective Stage in Host
Taenia saginata	Beef tapeworm	CATTLE	Cysticercus bovis (in muscle)
Taenia solium	Pork tapeworm	PIG (+ humans as dead-end accidental host)	Cysticercus cellulosae
Diphyllobothrium latum	Fish tapeworm	Copepods (1st), Freshwater fish (2nd)	Plerocercoid
Echinococcus granulosus	Dog tapeworm (hydatid)	Sheep/cattle/humans	Hydatid cyst

Taenia saginata life cycle:

Human (definitive host) passes eggs in feces
           ↓
Eggs ingested by CATTLE (intermediate host)
           ↓
Oncospheres hatch → penetrate intestinal wall → blood → muscles
           ↓
Develop into CYSTICERCUS BOVIS (cysts in muscle, "measly beef")
           ↓
Human eats undercooked beef containing cysticerci
           ↓
Cysticercus attaches to small intestine → grows into adult tapeworm
           ↓
Adult T. saginata (up to 10 METERS long, NO hooks - "unarmed" tapeworm)

T. saginata vs T. solium:

Feature	T. saginata	T. solium
Common name	Beef tapeworm	Pork tapeworm
Intermediate host	Cattle	Pig
Scolex	No hooks (unarmed)	Hooks + suckers (armed)
Length	Up to 10m	Up to 7m
Proglottids/week shed	~9	~6
Cysticercosis	Does NOT infect humans	CAN infect humans (neurocysticercosis)
Segments	More lateral uterine branches (>13)	Fewer (<13)

Prevention: Thorough cooking of beef (>65°C destroys cysticerci), proper sanitation

Q69. A 12-year-old boy with ascariasis (egg with mammillated outer shell). Treated, then presents with acute abdomen. Most likely complication?

Cholangitis
Cholecystitis
Intestinal obstruction ✓
Intestinal perforation

Answer: Intestinal obstruction

Explanation:

Ascaris lumbricoides (roundworm):

Largest intestinal nematode (adults: females 20-35cm, males 15-30cm)
Mammillated (bumpy/knobby) outer shell = characteristic egg appearance - confirming ascariasis
Most prevalent helminthic infection worldwide (~1 billion infected)

Why intestinal obstruction is the most common/classic complication:

Heavy worm burden (hundreds of worms in small intestine)
           ↓
Worms form a BOLUS / MASS in the lumen
           ↓
MECHANICAL INTESTINAL OBSTRUCTION
           ↓
Acute abdomen: severe colicky pain, vomiting, distension
           ↓
Plain X-ray: "whirlpool" pattern of worms

After anthelmintic treatment (e.g., albendazole, mebendazole):

Dying/dead worms become stiff → more likely to cause obstruction as they clump
This explains why the child developed acute abdomen AFTER treatment

Other complications of ascariasis:

Complication	Mechanism
Intestinal obstruction (most common)	Large worm bolus
Biliary ascariasis/Cholangitis	Adult worms migrate into CBD → jaundice, cholangitis
Pancreatitis	Worm enters pancreatic duct
Appendicitis	Worm in appendix
Liver abscess	Migration to liver
Loeffler's syndrome	Larvae migrating through lungs → eosinophilic pneumonitis
Nutritional deficiency	Competing for nutrients

Why cholangitis is also possible (but less common than obstruction): Ascaris adults can migrate through the ampulla of Vater into the bile duct → cholangitis, cholecystitis, or pancreatitis. However, intestinal obstruction is the most common complication overall.

Egg identification: Fertile eggs = oval, mammillated (bumpy albuminous coat), brown, thick-walled; infertile eggs = longer, irregular

Q70. A 35-year-old man with fever, abdominal pain and diarrhea. Stool microscopy: intestinal amoebiasis diagnosed. Most significant finding for identifying Entamoeba histolytica?

Ingested red blood cells ✓
Mass of glycogen
Pseudopodia
Spherical nucleus with central karyosome

Answer: Ingested red blood cells (erythrophagocytosis)

Explanation:

Pathognomonic finding of E. histolytica trophozoites: INGESTED RBCs (erythrophagocytosis)

Why ingested RBCs are MOST SIGNIFICANT:

E. histolytica is the ONLY Entamoeba species that phagocytoses red blood cells
The trophozoite contains visible RBCs within its cytoplasm (erythrophagocytosis)
This is the single most diagnostic feature distinguishing E. histolytica from:
- E. dispar (morphologically identical but NON-pathogenic, does NOT ingest RBCs)
- E. coli (non-pathogenic commensal, does NOT ingest RBCs)
- E. hartmanni (non-pathogenic, smaller)

Comparison of Entamoeba species:

Feature	E. histolytica (pathogenic)	E. dispar (non-pathogenic)	E. coli (non-pathogenic)
Ingested RBCs	YES - PATHOGNOMONIC	NO	NO
Nucleus	Spherical, fine peripheral chromatin, small central karyosome	Same	Eccentric/irregular karyosome
Cyst nuclei	1-4 (mature = 4)	Same	Up to 8
Pathogenicity	Yes (dysentery, liver abscess)	NO	NO

Why other options are less specific:

Pseudopodia: present in ALL amoebae (Entamoeba, Naegleria, Acanthamoeba, etc.) - non-specific
Mass of glycogen: glycogen vacuole seen in CYSTS of multiple Entamoeba species - non-specific
Spherical nucleus with central karyosome: seen in E. histolytica but ALSO in E. dispar (cannot distinguish between the two) - this is a nuclear morphology feature, not pathognomonic

E. histolytica pathogenesis:

Trophozoites lyse intestinal epithelium using Gal/GalNAc lectins → attach to colonocytes
Secrete pore-forming proteins (amoebapores) → cell lysis
Amoebiasis: flask-shaped ulcers in colon → bloody/mucoid diarrhea
Extraintestinal: liver abscess (most common extraintestinal site - "anchovy sauce" pus)

Q71. A 49-year-old man with colonic adenocarcinoma on chemotherapy. A drug acting on 5-HT3 receptors is prescribed for chemotherapy-induced nausea/vomiting (CINV). Which drug?

Diphenhydramine
Ondansetron ✓
Phenothiazine
Scopolamine

Answer: Ondansetron

Explanation:

Note on the question: The question says "acts on 5-HT2 receptors" but the correct answer is 5-HT3 receptor antagonist (ondansetron) - the question likely contains a typo (should be 5-HT3).

Ondansetron:

Class: 5-HT3 (serotonin type 3) receptor ANTAGONIST
Drug names: Ondansetron (Zofran), also granisetron, palonosetron ("setron" suffix)
Gold standard for chemotherapy-induced nausea and vomiting (CINV)

Mechanism of ondansetron:

Chemotherapy → damage to GI enterochromaffin cells
           ↓
MASSIVE SEROTONIN (5-HT) RELEASE
           ↓
5-HT activates 5-HT3 receptors on:
  1. Vagal afferents in GI tract
  2. Chemoreceptor trigger zone (CTZ) in area postrema (brainstem)
           ↓
Signal to vomiting center → NAUSEA and VOMITING
           ↓
ONDANSETRON blocks 5-HT3 receptors
           ↓
Prevents serotonin-mediated activation → ANTIEMETIC EFFECT

Drug comparison for CINV:

Drug	Mechanism	Use
Ondansetron	5-HT3 antagonist	CINV, PONV, radiation-induced
Diphenhydramine	H1 antihistamine	Motion sickness, mild nausea
Phenothiazines (prochlorperazine)	D2 antagonist	Nausea (older agent)
Scopolamine	Muscarinic antagonist	Motion sickness (transdermal patch)
Metoclopramide	D2 + 5-HT4 agonist	Gastroparesis, CINV (older)
Dexamethasone	Anti-inflammatory	Combined with ondansetron for CINV
Aprepitant	NK1 antagonist	Highly emetogenic chemotherapy

Q72. A 45-year-old man with epigastric pain prescribed famotidine. Mechanism of action?

It blocks histamine receptors ✓
It blocks the proton pump
It neutralizes gastric acid
It promotes mucosa production

Answer: It blocks histamine receptors (H2 receptor antagonist)

Explanation:

Famotidine belongs to the class of H2 receptor antagonists (H2 blockers):

Other members: cimetidine, ranitidine, nizatidine (all end in "-tidine")

Mechanism:

Parietal cell has 3 stimulatory receptors:
1. Histamine (H2) receptor
2. Gastrin receptor (CCK-B)
3. Acetylcholine receptor (M3)

All 3 activate H+/K+ ATPase (proton pump) → HCl secretion

FAMOTIDINE → competitively blocks H2 receptors on parietal cells
           ↓
Prevents histamine-mediated stimulation of acid secretion
           ↓
Reduced gastric acid → symptom relief for peptic ulcer, GERD

Drug mechanism comparison:

Drug/Class	Mechanism	Example
H2 blockers	Block H2 receptors on parietal cells	Famotidine, ranitidine, cimetidine
PPIs	Block H+/K+ ATPase (proton pump) irreversibly	Omeprazole, pantoprazole (-prazole)
Antacids	Chemically neutralize gastric acid	Aluminum hydroxide, magnesium hydroxide
Sucralfate	Promotes mucosa/cytoprotection	Sucralfate, misoprostol

H2 blockers vs PPIs:

H2 blockers: less potent, faster onset, used for mild-moderate GERD/peptic ulcer
PPIs: more potent (90% acid reduction vs 70% with H2 blockers), irreversible, better for severe GERD, Barrett's, H. pylori eradication (combined with antibiotics)

H2 blocker clinical uses:

Peptic ulcer disease (gastric and duodenal ulcers)
GERD (mild to moderate)
Zollinger-Ellison syndrome (high gastrin states)
Stress ulcer prophylaxis in ICU patients (along with PPIs)

Side effects (especially cimetidine):

Cimetidine: anti-androgenic effects (gynecomastia, impotence), inhibits CYP450 enzymes → drug interactions
Famotidine: fewer drug interactions, generally well-tolerated

Q73. A 23-year-old man with rice-water watery diarrhea after street food. Suspected cholera. Which therapy is CONTRAINDICATED?

Antimicrobial therapy
Antimotility therapy ✓
Antisecretory therapy
Fluid replacement therapy

Answer: Antimotility therapy (e.g., loperamide) is contraindicated

Explanation:

Cholera caused by Vibrio cholerae (Gram-negative, comma-shaped, non-invasive):

Produces cholera toxin (CT): ADP-ribosylates Gs-alpha → constitutively active adenylyl cyclase → ↑cAMP → CFTR chloride channel stays open → massive Cl- secretion → Na+ and water follow → profuse watery (rice-water) diarrhea
Non-invasive - stays in intestinal lumen (no tissue invasion, no bloody diarrhea)
Fluid loss can reach 10-20 liters/day → life-threatening dehydration and electrolyte imbalance

Why antimotility drugs (loperamide, diphenoxylate) are CONTRAINDICATED:

Antimotility drugs reduce intestinal peristalsis → fluid and toxin-producing bacteria are retained in the intestine longer
In cholera, the toxin continues to act → continued massive fluid secretion with no flushing → worsened dehydration
Bacterial stasis → increased toxin production
In cholera, motility is already actually reduced (intestinal ileus from toxin) - stopping motility further worsens fluid accumulation

In contrast, why other therapies are INDICATED:

Fluid replacement: MOST IMPORTANT - oral rehydration solution (ORS) is the cornerstone of treatment; IV fluids for severe dehydration (Ringer's lactate)
Antimicrobial therapy: shortens illness duration and reduces bacterial shedding; doxycycline (drug of choice), azithromycin (children/pregnant), ciprofloxacin
Antisecretory: experimental approaches; not typically first-line but not contraindicated

ORS composition (WHO): Na+ 75 mmol/L, Cl- 65 mmol/L, K+ 20 mmol/L, glucose 75 mmol/L, citrate 10 mmol/L (osmolarity 245 mOsmol/L)

Q74. A 52-year-old man with unilateral leg swelling diagnosed with filariasis. Which antiparasitic drug is indicated?

Albendazole
Diethylcarbamazine (DEC) ✓
Ivermectin
Pyrantel pamoate

Answer: Diethylcarbamazine (DEC)

Explanation:

Lymphatic filariasis with lymphedema (unilateral leg swelling = early lymphedema):

Filariasis causative agents:

Wuchereria bancrofti (~90%), Brugia malayi, B. timori
Transmitted by Culex, Anopheles, Aedes mosquitoes
Adults in lymphatics → inflammation → lymphatic obstruction → lymphedema (leg, scrotal)
Late stage: elephantiasis (massive limb enlargement)

DEC (Diethylcarbamazine) - Drug of choice for individual treatment:

Mechanism of DEC:

Immobilizes microfilariae (alters surface charge → enhanced phagocytosis)
Kills both microfilariae AND adult worms (direct filaricidal + immune-mediated)
Reduces worm burden → decreases lymphatic inflammation → halts progression

Antifilarial drug comparison:

Drug	Kills Microfilariae	Kills Adults	Use
DEC	Yes	Yes	Individual treatment (drug of choice)
Ivermectin	Yes (microfilariae only)	Partial	MDA programs, onchocerciasis
Albendazole	Weak	Yes (slow)	MDA programs (combined with DEC or ivermectin)
DEC + Albendazole	Yes + Yes	Yes + Yes	WHO MDA program

WHO MDA regimen:

DEC + albendazole: annual single-dose MDA for lymphatic filariasis elimination
Ivermectin + albendazole: in areas co-endemic with onchocerciasis (DEC causes adverse reactions in onchocerciasis)

Why not pyrantel pamoate? Used for intestinal nematodes (roundworm, hookworm, pinworm) - has NO activity against tissue-dwelling filarial worms

Q75. A 9-year-old boy with oliguria, cola-colored urine, periorbital edema, hypertension, elevated creatinine after sore throat. Most likely finding in urine microscopy?

Eosinophilic casts
Muddy brown casts
RBC casts ✓
WBC casts

Answer: RBC casts

Explanation:

This is Post-Streptococcal Glomerulonephritis (PSGN) - same presentation as Q24 (earlier set).

Classic presentation:

Age: school-age children (5-12 years)
Preceding infection: Group A Streptococcus (GAS) throat infection (pharyngitis) - 1-3 week latent period
Nephritic syndrome: hematuria (cola/smoky urine), oliguria, hypertension, edema (periorbital)
Elevated creatinine/urea (reduced GFR)
Hypocomplementemia (↓C3) - classic

RBC casts - pathognomonic of glomerulonephritis:

Streptococcal antigens → immune complex formation
           ↓
Immune complexes deposit in glomerular mesangium and subendothelium
           ↓
Complement activation → neutrophil infiltration
           ↓
Glomerular capillary wall damage → RBCs leak into tubular lumen
           ↓
RBCs + Tamm-Horsfall protein → RBC CASTS form in tubules
           ↓
RBC casts in urine = GLOMERULAR ORIGIN hematuria

Cast differentiation:

Cast	Disease	Mechanism
RBC casts	Glomerulonephritis	GBM damage → RBC leak
WBC casts	Pyelonephritis, AIN	WBC infiltration of tubules
Muddy brown (granular)	ATN	Epithelial cell necrosis
Fatty casts	Nephrotic syndrome	Lipid in tubules
Eosinophilic casts	Allergic interstitial nephritis	Drug reaction
Hyaline	Normal/dehydration	Tamm-Horsfall only

Muddy brown granular casts = acute tubular necrosis (ATN) - from ischemia or nephrotoxins.

Q76. A 3-year-old boy with irritability and hematuria. CT shows 3.1 cm right renal mass. Histology shows TRIPHASIC malignant neoplasm: blastemal, stromal, and epithelial tissues. Which renal neoplasm?

Clear cell renal cell carcinoma
Papillary renal cell carcinoma
Rhabdoid tumour of kidney
Wilms tumour ✓

Answer: Wilms Tumour (Nephroblastoma)

Explanation:

Triphasic histology (blastema + stroma + epithelium) = WILMS TUMOUR - this is pathognomonic.

Wilms Tumour (Nephroblastoma):

Most common renal malignancy in children (peak age: 3-4 years)
Arises from metanephric blastema (embryonic renal precursor cells)
90% present before age 6

Classic triphasic histology:

Component	Description
Blastemal	Densely packed small blue cells (undifferentiated embryonic cells)
Stromal	Loose mesenchymal tissue (spindle cells, smooth muscle, adipose)
Epithelial	Tubular/glomeruloid structures

All three components present = "favorable histology" (better prognosis) Anaplasia = "unfavorable histology" = worse prognosis

Clinical features:

Asymptomatic abdominal mass (most common presentation) - parents notice while bathing child
Hematuria (20-25%)
Hypertension (due to renin secretion)
Abdominal pain, fever

Important associations:

WAGR syndrome: Wilms tumour + Aniridia + Genitourinary anomalies + mental Retardation (WT1 gene deletion, chromosome 11p13)
Beckwith-Wiedemann syndrome: organomegaly, macroglossia, hemihypertrophy (WT2 gene, IGF2 overexpression)
Denys-Drash syndrome: WT1 mutation, Wilms tumour + pseudohermaphroditism + nephropathy

Genetics:

WT1 gene (chromosome 11p13): tumor suppressor, Knudson two-hit hypothesis
WT2 gene (chromosome 11p15)
β-catenin (CTNNB1) mutations

Treatment: Surgery (nephrectomy) + chemotherapy (vincristine, actinomycin D, adriamycin) ± radiotherapy. Excellent prognosis (~90% 4-year survival for favorable histology stage I-II)

Why not others?

Clear cell RCC: adults (50-70y), uniphasic (clear cytoplasm), NOT triphasic
Papillary RCC: adults, papillary architecture, NOT triphasic
Rhabdoid tumour: highly aggressive, large cells with prominent nucleolus, cytoplasmic inclusions, NOT triphasic

Q77. A 35-year-old man in hypovolemic shock from road traffic accident. Develops oliguria, elevated urea/creatinine, urine shows GRANULAR CASTS. Most likely disorder?

Acute papillary necrosis
Acute tubular necrosis ✓
Prerenal azotemia
Tubulointerstitial nephritis

Answer: Acute tubular necrosis (ATN)

Explanation:

Key finding: Granular (muddy brown) casts = ATN

Pathogenesis:

Hypovolemic shock (road traffic accident)
           ↓
Decreased renal perfusion pressure
           ↓
Renal ischemia → ATP depletion in tubular cells
           ↓
Na+/K+ ATPase fails → cell swelling → TUBULAR CELL NECROSIS
           ↓
Necrotic cells slough into tubular lumen
           ↓
Necrotic debris + Tamm-Horsfall protein → 
GRANULAR (MUDDY BROWN) CASTS
           ↓
Oliguric ARF

Phases of ATN:

Phase	Duration	Features
Initiation	Hours	Ischemic insult, mild azotemia
Maintenance (oliguric)	1-2 weeks	Oliguria, rising creatinine, electrolyte imbalance
Recovery (polyuric)	1-2 weeks	Urine output increases, tubules regenerate, may have tubular dysfunction

Distinguishing prerenal azotemia from ATN:

Feature	Prerenal Azotemia	ATN
Mechanism	Decreased perfusion, tubules intact	Tubular cell necrosis
Urine Na	<20 mEq/L (tubules reabsorb Na avidly)	>40 mEq/L (tubules cannot reabsorb)
FENa	<1%	>2%
Urine osmolality	>500 mOsmol/kg (concentrated)	~350 mOsmol/kg (dilute, cannot concentrate)
Urine sediment	Normal, hyaline casts	Granular/muddy brown casts + renal tubular epithelial cells
Response to fluids	Responds (reversible)	Does NOT respond
Creatinine	Elevated	Elevated (higher)

This patient had prolonged hypovolemia → initially prerenal → if not corrected → progresses to ischemic ATN (intrinsic renal failure) + granular casts confirm ATN.

Q78. A 32-year-old woman with dysuria and clear urethral discharge. Non-gonococcal urethritis with Chlamydia trachomatis detected. Which diagnostic test for SEROVAR CONFIRMATION?

Complement fixation test
Culture on McCoy cells
Direct fluorescent antibody test
Microimmunofluorescence test ✓

Answer: Microimmunofluorescence (MIF) test

Explanation:

Why serovar identification matters for Chlamydia trachomatis:

C. trachomatis serovars have different clinical presentations:

Serovar	Disease
A, B, Ba, C	Trachoma (blinding eye disease)
D-K	Genital infections (urethritis, cervicitis, PID, epididymitis) + neonatal infections
L1, L2, L3	Lymphogranuloma venereum (LGV)

This patient has genital tract infection → likely serovar D-K.

Microimmunofluorescence (MIF) test:

Gold standard for Chlamydia serovar typing
Uses serovar-specific antibodies labeled with fluorescent dye
Can differentiate between all C. trachomatis serovars
Detects species-specific and serovar-specific antibodies in patient serum
Used for: seroepidemiological studies, distinguishing genital infection from LGV

Chlamydia diagnostic tests:

Test	Use	Notes
NAAT (nucleic acid amplification test)	Clinical diagnosis of genital chlamydia	Most sensitive, first-line in clinical practice
MIF test	Serovar confirmation	Research/epidemiology, LGV diagnosis
Culture on McCoy cells	Confirms viability, research	Difficult, insensitive (~70%), not routine
Direct FA test (DFA)	Rapid antigen detection	Less sensitive than NAAT
Complement fixation test	Detects genus-specific antibody	Non-specific (positive in any Chlamydophila infection)

Why not the others?

Culture on McCoy cells: confirms presence but does NOT distinguish serovars specifically
DFA: detects chlamydial antigens but does not distinguish serovars
Complement fixation: genus-level antibody, not serovar-specific

Q79. A 25-year-old woman with 3 days of high-grade fever, chills, rigors, and flank pain. Diagnosed with acute pyelonephritis. Expected finding in urine analysis?

Bacterial count 1,000 cells/mL
High glucose level
High red blood cell count
Presence of white blood cell casts ✓

Answer: Presence of white blood cell (WBC) casts

Explanation:

WBC casts = diagnostic hallmark of upper urinary tract infection (acute pyelonephritis)

Why WBC casts are pathognomonic of pyelonephritis:

Bacteria ascend from bladder → ureter → renal pelvis → tubules
           ↓
Neutrophils recruited to fight infection in RENAL TUBULES
           ↓
WBCs enter tubular lumen from interstitium
           ↓
WBCs + Tamm-Horsfall protein → WBC CASTS form in tubules
           ↓
WBC casts in urine = infection is in the KIDNEY (not just bladder)

This is the key distinction:

Lower UTI (cystitis): WBCs and bacteria in urine, no casts
Upper UTI (pyelonephritis): WBCs and bacteria + WBC casts (casts confirm renal involvement)

Complete urine analysis findings in acute pyelonephritis:

Finding	Significance
WBC casts	Pathognomonic of pyelonephritis
Pyuria (>10 WBCs/HPF)	Infection
Bacteriuria (>100,000 CFU/mL)	Significant bacteriuria
Nitrite positive	Gram-negative bacteria convert nitrate
Leukocyte esterase positive	Indicates WBCs
Mild hematuria	Possible but not the main finding
Proteinuria	Mild

Why "bacterial count 1,000 cells/mL" is wrong?

Significant bacteriuria in symptomatic UTI = ≥100,000 CFU/mL (10^5)
1,000 CFU/mL may represent contamination, not true infection

Why "high glucose" is wrong?

Glucosuria = diabetes mellitus or proximal tubule damage (Fanconi syndrome) - not pyelonephritis
Pyelonephritis does not cause glucosuria (unless patient is also diabetic)

Q80. A 37-year-old woman with severe right flank pain and hematuria, diagnosed with renal calcium oxalate stones. Which diuretic prevents future stone formation?

Ethacrynic acid
Furosemide
Hydrochlorothiazide ✓
Spironolactone

Answer: Hydrochlorothiazide (thiazide diuretic)

Explanation:

Thiazide diuretics for calcium oxalate nephrolithiasis:

Mechanism of hydrochlorothiazide (HCTZ) in preventing calcium stones:

HCTZ acts on early distal convoluted tubule (DCT)
           ↓
Blocks NCC (Na-Cl cotransporter)
           ↓
Reduces intracellular Na+ in DCT cells
           ↓
Activates basolateral Na+/Ca2+ exchanger
           ↓
INCREASED tubular calcium reabsorption from lumen
           ↓
DECREASED urinary calcium excretion (HYPOCALCIURIA)
           ↓
Less calcium available in urine to precipitate with oxalate
           ↓
PREVENTS calcium oxalate stone formation

Other measures to prevent calcium oxalate stones:

High fluid intake (>2.5 L/day) - most important
Restrict sodium (high Na → increased calciuria)
Moderate calcium intake (do NOT restrict - dietary Ca binds intestinal oxalate)
Restrict animal protein
Potassium citrate (alkalinizes urine, inhibits stone crystallization)

Diuretic comparison for nephrolithiasis:

Diuretic	Effect on Urine Calcium	Stone Prevention
Thiazides (HCTZ)	DECREASES (↓Ca excretion)	YES - calcium stones
Loop diuretics (furosemide)	INCREASES Ca excretion	NO - worsens calcium stones
Acetazolamide	Increases Ca, alkalinizes urine	Can promote calcium phosphate stones
Spironolactone	Minimal effect on Ca	Not used for nephrolithiasis

Why loop diuretics are WRONG:

Furosemide and ethacrynic acid (loop diuretics) block the NKCC2 transporter in the thick ascending limb
This reduces calcium reabsorption at the loop → hypercalciuria → WORSENS calcium stone disease
Furosemide is actually used to TREAT hypercalcemia (by increasing calcium excretion)

Summary: For calcium oxalate stone prevention → thiazide diuretic (HCTZ) to reduce urinary calcium.

Summary Table - Q61 to Q80

Q	Answer	Core Concept
61	Reflux esophagitis	GERD → Barrett's (intestinal metaplasia) → adenocarcinoma at lower esophagus
62	Reduced gastroprotective prostaglandins	H. pylori → prostaglandin depletion → mucosal vulnerability
63	Intussusception	Telescoping intestine; post-viral gastroenteritis; 6-36 months age group
64	Pancreatic pseudocyst	2 weeks post-pancreatitis + mass + obstructive jaundice from compression
65	Non-lactose fermenter	S. typhi = Gram-negative, facultative anaerobe, motile, non-lactose fermenter
66	Salmonella typhimurium	Half-boiled eggs + non-lactose fermenter = Salmonella gastroenteritis
67	Haematemesis	S. mansoni (lateral spine) → portal fibrosis → varices → haematemesis
68	Cattle	T. saginata = beef tapeworm; cattle = intermediate host
69	Intestinal obstruction	Ascaris worm bolus; mammillated egg; after treatment = dying worms clump
70	Ingested red blood cells	Erythrophagocytosis = pathognomonic of E. histolytica
71	Ondansetron	5-HT3 antagonist = gold standard for CINV
72	Blocks histamine receptors	Famotidine = H2 blocker; PPIs block proton pump
73	Antimotility therapy	Loperamide contraindicated in cholera - retains toxin + worsens dehydration
74	Diethylcarbamazine	DEC = drug of choice for filariasis; kills micro + macrofilariae
75	RBC casts	Post-streptococcal GN = glomerular damage → RBC leakage
76	Wilms tumour	Triphasic (blastema + stroma + epithelium) = nephroblastoma, age 3-4 years
77	Acute tubular necrosis	Hypovolemic shock → ischemic ATN → granular (muddy brown) casts
78	Microimmunofluorescence test	Gold standard for C. trachomatis serovar typing
79	WBC casts	Pyelonephritis = kidney infection → WBCs in tubules → WBC casts
80	Hydrochlorothiazide	Thiazides ↓urine Ca → prevent calcium oxalate stones; loop diuretics worsen it

81. A 55-year-old woman presents with bilateral pedal oedema. She has a history of chronic back pain. She is on treatment with ibuprofen for the past two years. She is found to have impaired renal function and is suspected to have drug-induced nephrotoxicity. Which of the following mechanisms best explains the nephrotoxic effect of the above drug? A. It reduces glomerular blood flow B. It causes the formation of crystals in the kidney C. It leads to the formation of renal thrombi D. It produces direct tubular cell toxicity 82. A 9y/o kid diagnosed with minimal change disease. He is treated with oral prednisolone. After Two Weeks of Treatment, the proteinuria and oedema improved treatment stopped. Which of the following mechanisms of action best describes the above drug? A. It inhibits phospholipase A2 B. It inhibits prostaglandin synthesis. C. It stabilizes the actin cytoskeleton D. It suppresses T-lymphocytes. 83. A 34-year-old married woman presents to the clinic with lower abdominal pain and infertility. A laparoscopy is performed, and a nodular lesion is seen. A biopsy of the lesion confirms the diagnosis of endometriosis. Which of the following pathologic changes is most likely to be seen ni the biopsy of the above lesion? A. Endometrial glands and stroma B. Granulomatous inflammation C. Koilocytosis with nuclear atypia D. Myometrial smooth muscle cells 84. A 17-year-old girl presents to the gynaecologist with oligomenorrhoea for the past one year. On examination she is obese, has hirsutism and acne. Following investigations, she is diagnosed with Polycystic Ovary Syndrome (PCOS). Which factor causes oligomenorrhoea in this patient? A. Chronic anovulation B. Endometrial hyperplasia, C. Multiple ovarian cysts D. Subcortical fibrosis in ovaries 85. A 56-year-old woman presents with a firm irregular 2-cm mass in her left breast for 4 months. Histologic examination of the mass shows the presence of discohesive infiltrating tumour cells invading perilobular connective tissue in a single-file, pattern Immunohistochemical staining of these cells shows an absence of E-cadherin and HER2, but the presence of Estrogen Receptor (ER) and Progesterone Receptor (PR). Which of the following malignant lesions is the most likely diagnosis for this patient? A. Ductal carcinoma B. Lobular carcinoma C. Medullary carcinoma D. Metaplastic Carcinoma 86. A 55-year-old man presents with urinary hesitancy for the past 8 months. Digital rectal examination reveals an enlarged non-tender prostate with no hard areas. Biopsy from the prostate shows proliferation of glands and stroma-forming nodules. The glands are lined by epithelial and basal cell layers. Which of the following conditions is the most likely cause of prostatic enlargement in this patient? A. Acute prostatitis B. Adenocarcinoma Of prostate C. Benign prostatic hyperplasia D. Granulomatous prostatitis 87. A 40-year-old man presents to the clinic with a non-itchy rash on the trunk, extremities, palms and soles for three months. On examination, Condyloma latum is observed in the peri-anal region. A Provisional diagnosis of secondary syphilis is made. Which of the following lab investigations is the most appropriate confirmatory test for this condition? A. Culture of the exudate B. ELISA to detect antibodies C. Rapid Reagin Test D. Polymerase chain reaction 88. A 32-year-old woman presents to the outpatient clinic with dysuria and mucopurulent discharge from genitalia for the past three days. Diagnosis of gonorrhoea is made based on microbiological investigations. Which of the following structural components of the above causative organism is most important in its colonization of urogenital epithelium? A. Lipooligosaccharide B. Major outer membrane porin proteins C. Opacity proteins D. Type IV pili 89. A 56-year-old woman presents to the Gynecology Clinic with complaints of dyspareunia and post-coital vaginal bleeding for one-month duration. Following investigations, she was diagnosed with cervical carcinoma associated with human papillomavirus. Which of the following mechanisms is the most likely cause for the above diagnosis? A. Inactivation of the p53 and RB proteins B. presence of an abnormal number of centromeres C. Virus replication in the basal cell D. Down-regulation of tumour necrosis factor receptors 90. A 45-year-old patient is diagnosed with meningitis due to Cryptococcusneoformans The physician starts treatment with a combination of amphotericin B and flucytosine. Which of the following effects best explains the reason for the combination of the above drugs? A. It enhances the spectrum of antifungal activity. B. It improves the penetration of drug into the CNS. C. It prevents the antifungal resistance. D. It reduces the side effects of amphotericin B. 91. A 30-year-old pregnant woman comes for regular antenatal follow-up. Her blood pressure is 140/105 mmH. Following subsequent visits, she is diagnosed with hypertension. The physician plans to start her on antihypertensive medication. Which of the following antihypertensive drugs is most likely to be contraindicated for this patient? A. Enalapril B. Labetalol C. Methyldopa D. Nifedipine 92. A 34-year-old woman visits the clinic for family planning. After a thorough history, the physician decides not to prescribe her the combined oral contraceptive pill. Which of the following history would be the most likely reason for the physician's decision? A. She has family history of ovarian cyst. B. She has history of abortion. C. She has history of deep vein thrombosis. D. She has history of irregular menses 93. A 41-year-old woman is diagnosed with Invasive Breast carcinoma. immunohistochemistry reveals neoplastic cells positive for estrogen Receptor. She is treated with anticancer therapy together with long-term tamoxifen. Which of the following side effects is most likely to develop due to the long-term medication with the above drug? A. Deep vein thrombosis B. Oligomenorrhoea C. Pulmonary embolism D. Uterine cancer 94. A 45-year-old male presents with episodes of seizure. Radio imaging reveals a solitary, circumscribed 3 cm mass in the right parietal lobe. Microscopically, the mass consists of sheets of cells with round nuclei that show a fried egg appearance, chicken-wire vasculature pattern and areas of calcification. Which of the following central nervous system neoplasms best fits with the above description? A. Ependymoma B. Glioblastoma C. Meningioma D. Oligodendroglioma 95. A group of researchers are conducting a retrospective study on the cases of hypertensive intracerebral haemorrhage that presented in a tertiary care hospital over the past ten years. Which of the following anatomical parts of the brain is most likely to be observed as the commonest location of the above condition in the above study? A. Basal ganglia B. Cerebellum C. Cerebral hemisphere D. Pons 96. A 35-year-old woman presents with a history of headache, vomiting and blurring of vision. She is suspected to have intracranial lesion. CT-scan of the brain shows presence of small intracranial mass and hydrocephalus with dilated lateral and 3rd ventricles. The 4th ventricle is normal. Which of the following types of hydrocephalus is described in this case? A. Communicating B. Ex-vacuo C. Non-communicating D. Normal pressure hydrocephalus 97. A 72-year-old male is brought to the physician by his son with a history of forgetfulness and inability to perform daily life activities. Following assessment, he is diagnosed with dementia due to Alzheimer's disease. Which of the following neuronal protein accumulates is most likely to be present in this patient's brain? A. Alpha-synuclein in basal ganglia B. Aß amyloid plaques in neocortex C. Huntingtin in the caudate nucleus D. Ubiquitin in frontal and temporal lobes 98. A 28-year-old man presents with acute neurological signs. Two months ago, he was bitten by a stray dog. He sustained an injury to the forearm with skin break and surrounding tissue damage. Rabies is suspected. Which of the following laboratory methods is most specific to detect the causative agent? A. CSF profiling B. Detection of anti-rabies IgM C. Detection of Negri bodies D. Detection of viral antigen 99. A 5-year-old boy has been admitted to the Emergency Department with high fever, headache and vomiting for the past two days. On examination, his temperature is 40°C. Other vital signs are normal. Babinski's test is positive. The results of the CSF examination reveal Neisseria meningitidis. Which of the following virulence factors is most likely to play a major role in the survival of this causative agent in the bloodstream? A. Capsule B. Opacity proteins C. Pilli D. protease

Here are all 19 questions (Q81-Q99) answered fully:

Q81. A 55-year-old woman on ibuprofen for 2 years develops bilateral pedal edema and impaired renal function. Mechanism of nephrotoxicity?

It reduces glomerular blood flow ✓
It causes crystal formation
It leads to renal thrombi
It produces direct tubular cell toxicity

Answer: It reduces glomerular blood flow

Explanation:

Ibuprofen = NSAID (Non-Steroidal Anti-Inflammatory Drug) - COX-1 and COX-2 inhibitor

Mechanism of NSAID-induced nephrotoxicity:

Normal kidney physiology:
Afferent arteriole tone maintained by balance of:
  VASOCONSTRICTORS (angiotensin II, norepinephrine)
  vs
  VASODILATORS (prostaglandins: PGE2, PGI2) ← synthesized locally by COX

In states of reduced renal perfusion:
(elderly, CHF, cirrhosis, dehydration, CKD, hypovolemia)
           ↓
RAAS activated → angiotensin II → vasoconstriction
           ↓
Kidney relies on LOCAL PROSTAGLANDINS (PGE2, PGI2)
to DILATE the afferent arteriole and maintain GFR
           ↓
IBUPROFEN (COX inhibitor) → BLOCKS prostaglandin synthesis
           ↓
Afferent arteriole CONSTRICTS unopposed
           ↓
REDUCED GLOMERULAR BLOOD FLOW → REDUCED GFR
           ↓
Acute kidney injury (oliguria, elevated creatinine, edema)

Clinical consequences of NSAID nephrotoxicity:

Mechanism	Result
↓Prostaglandins → afferent arteriole constriction	Reduced GFR (hemodynamic AKI)
↓Prostaglandins → ↓renin → ↑aldosterone blockade	Hyperkalemia
Direct interstitial nephritis (hypersensitivity)	Chronic interstitial nephritis, papillary necrosis
↓Prostaglandins → sodium retention	Edema, hypertension

This patient: 2 years of ibuprofen use → chronic prostaglandin suppression → reduced GFR + sodium/water retention → bilateral pedal edema + renal impairment

Risk factors for NSAID nephrotoxicity:

Elderly (>60y)
Pre-existing CKD
Heart failure, cirrhosis (already prostaglandin-dependent)
Hypovolemia/dehydration
Concurrent ACE inhibitors/ARBs (triple whammy: NSAID + ACEi + diuretic = high AKI risk)

Why not crystal nephropathy? - That is caused by sulfonamides, acyclovir, methotrexate, uric acid - not NSAIDs Why not direct tubular toxicity? - That is aminoglycosides, cisplatin, contrast agents, amphotericin B

Q82. A 9-year-old with minimal change disease treated with oral prednisolone - proteinuria and edema improved after 2 weeks. Mechanism of action of prednisolone?

It inhibits phospholipase A2
It inhibits prostaglandin synthesis
It stabilizes the actin cytoskeleton
It suppresses T-lymphocytes ✓

Answer: It suppresses T-lymphocytes

Explanation:

Minimal Change Disease (MCD):

Most common cause of nephrotic syndrome in children (peak 2-6 years)
Light microscopy: normal glomeruli (no visible changes - hence "minimal change")
Electron microscopy: diffuse podocyte foot process effacement (fusion)
Immunofluorescence: negative (no immune deposits)
Excellent response to corticosteroids (~90% remission)

Pathogenesis of MCD:

Believed to be caused by T-lymphocyte dysfunction → abnormal T-cell clone releases a circulating permeability factor (possibly vascular permeability factor/soluble urokinase receptor)
This factor injures podocytes → foot process effacement → loss of charge barrier and structural barrier → massive proteinuria (nephrotic range)

Why prednisolone works - by suppressing T-lymphocytes:

T-lymphocyte dysfunction → permeability factor released
           ↓
PREDNISOLONE suppresses T-lymphocytes
  (inhibits lymphokine production, reduces T-cell proliferation,
   induces lymphocyte apoptosis)
           ↓
Reduced circulating permeability factor
           ↓
Podocyte foot processes recover → charge/structural barrier restored
           ↓
Proteinuria resolves → edema resolves

Why not "inhibits phospholipase A2"?

This is the mechanism of glucocorticoids in general (via lipocortin/annexin-1 induction → inhibits PLA2 → reduces arachidonic acid → reduces prostaglandins and leukotrienes)
This is more relevant to the anti-inflammatory effect, not the specific mechanism in MCD

Why not "inhibits prostaglandin synthesis"?

This is the mechanism of NSAIDs (COX inhibition), not corticosteroids

Why not "stabilizes actin cytoskeleton"?

This describes some of the direct podocyte-protective effects but is not the primary pharmacological mechanism of prednisolone

For MCD specifically: The response is mediated through T-cell suppression → reduced permeability factor → podocyte recovery.

Q83. A 34-year-old woman with lower abdominal pain and infertility. Laparoscopy shows nodular lesion confirmed as endometriosis. Most likely pathological finding on biopsy?

Endometrial glands and stroma ✓
Granulomatous inflammation
Koilocytosis with nuclear atypia
Myometrial smooth muscle cells

Answer: Endometrial glands and stroma

Explanation:

Endometriosis:

Presence of endometrial glands AND stroma OUTSIDE the uterine cavity
The ectopic endometrial tissue responds to hormonal cycles just like normal endometrium → cyclical bleeding → inflammation → fibrosis → adhesions

Histological definition and criteria:

The diagnosis of endometriosis requires the presence of BOTH:
1. Endometrial glands (lined by columnar epithelium, may show secretory changes)
2. Endometrial stroma (characteristic ovoid stromal cells with scant cytoplasm)
Hemosiderin-laden macrophages (evidence of old hemorrhage) - supportive finding
Smooth muscle metaplasia may surround the implants

Why both glands AND stroma are required:

Isolated endometrial glands without stroma → could be endometriosis-related glandular cysts or mucinous cysts
Isolated stroma without glands → insufficient for diagnosis
The combination = definitive diagnosis of endometriosis

Common locations (in decreasing frequency):

Ovaries (most common) → "chocolate cysts" (endometriomas - old blood resembles chocolate)
Uterosacral ligaments
Rectovaginal septum
Pelvic peritoneum
Appendix, bladder, bowel

Clinical features: Dysmenorrhea (cyclic pelvic pain), dyspareunia, dyschezia, infertility, pelvic mass

"Powder burn lesions" on laparoscopy = classic endometriotic implants (dark blue/black spots)

Why not others?

Granulomatous inflammation: seen in tuberculosis, sarcoidosis, Crohn's - not endometriosis
Koilocytosis: HPV-infected squamous cells of cervix - not endometriosis
Myometrial smooth muscle: describes adenomyosis (endometrial glands WITHIN myometrium, not ectopic)

Q84. A 17-year-old girl with oligomenorrhea, obesity, hirsutism, and acne. Diagnosed with PCOS. What causes the oligomenorrhea?

Chronic anovulation ✓
Endometrial hyperplasia
Multiple ovarian cysts
Subcortical fibrosis in ovaries

Answer: Chronic anovulation

Explanation:

PCOS (Polycystic Ovary Syndrome) pathophysiology and how it causes oligomenorrhea:

PCOS pathophysiology:
↑LH:FSH ratio → ↑LH stimulates theca cells → ↑Androgens (testosterone, androstenedione)
           ↓
Insulin resistance (obesity) → ↑Insulin → ↑IGF-1 → further stimulates theca cells → ↑Androgens
           ↓
Excess androgens → converted peripherally (adipose) to estrone (weak estrogen)
           ↓
Chronic constant estrogen (no cyclical variation) → tonic LH stimulation
           ↓
FOLLICLES FAIL TO MATURE → NO DOMINANT FOLLICLE → NO OVULATION
           ↓
CHRONIC ANOVULATION
           ↓
No corpus luteum → NO PROGESTERONE
           ↓
No progesterone withdrawal → NO MENSTRUATION
           ↓
OLIGOMENORRHEA / AMENORRHEA

Why "chronic anovulation" and NOT "multiple ovarian cysts":

The cysts in PCOS are arrested antral follicles (2-9mm, peripheral, "string of pearls" on US)
The cysts are the result of anovulation, not the cause of oligomenorrhea
The cysts do not mechanically obstruct the uterus
Oligomenorrhea is CAUSED by lack of ovulation and absence of progesterone withdrawal

PCOS diagnostic criteria (Rotterdam - 2 of 3):

Oligo/anovulation (oligomenorrhea/amenorrhea)
Clinical or biochemical hyperandrogenism (hirsutism, acne, elevated testosterone)
Polycystic ovaries on ultrasound (≥12 follicles of 2-9mm, or ovarian volume >10mL)

Rotterdam criteria: 2 of 3 required - this patient has all 3: oligomenorrhea + hirsutism/acne + likely polycystic ovaries

Q85. A 56-year-old woman with 2 cm left breast mass. Histology: discohesive infiltrating cells in single-file pattern. IHC: absent E-cadherin, absent HER2, present ER and PR. Diagnosis?

Ductal carcinoma
Lobular carcinoma ✓
Medullary carcinoma
Metaplastic carcinoma

Answer: Invasive Lobular Carcinoma (ILC)

Explanation:

Pathognomonic features of Invasive Lobular Carcinoma:

Feature	This Patient	ILC
Cell pattern	Discohesive, single-file ("Indian file")	CLASSIC for ILC
E-cadherin	ABSENT	Always negative in ILC
HER2	Absent	Usually negative
ER/PR	PRESENT	Usually positive (70-90%)
Architecture	Perilobular invasion, targetoid growth	Yes

Why E-cadherin loss is diagnostic of ILC:

E-cadherin = transmembrane glycoprotein that mediates cell-cell adhesion (epithelial adhesion)
In ILC: CDH1 gene mutation/inactivation → loss of E-cadherin → cells lose cohesion → grow in single file lines (Indian file pattern)
Loss of E-cadherin is the molecular hallmark of lobular carcinoma
Ductal carcinoma: E-cadherin POSITIVE

Invasive breast cancer comparison:

Feature	IDC (Ductal)	ILC (Lobular)
Frequency	~70-75%	~10-15%
Architecture	Gland formation, sheets	Single-file, targetoid (bull's eye)
E-cadherin	Positive	Negative
Hormone receptor	Often positive	Often ER/PR positive
HER2	Variable	Usually negative
Bilateral	Less common	More common (bilateral)
Detection	Palpable mass	Difficult to detect (no desmoplasia)
Metastasis	Lung, liver, bone	Gastrointestinal, peritoneum, ovaries, meninges

Why not medullary carcinoma?

Medullary carcinoma: large cells with syncytial architecture, prominent lymphocytic infiltrate, NO single-file pattern, usually triple-negative

Q86. A 55-year-old man with urinary hesitancy for 8 months. DRE shows enlarged, non-tender prostate with no hard areas. Biopsy: gland and stroma nodules with TWO cell layers (epithelial + basal). Most likely cause?

Acute prostatitis
Adenocarcinoma of prostate
Benign prostatic hyperplasia ✓
Granulomatous prostatitis

Answer: Benign Prostatic Hyperplasia (BPH)

Explanation:

Key diagnostic clues:

Feature	Significance
Age 55, male	BPH peak incidence 50-80y
Urinary hesitancy, obstructive symptoms	Lower urinary tract symptoms (LUTS)
Non-tender prostate	Rules out acute prostatitis (tender)
No hard areas on DRE	Against carcinoma (hard, nodular = cancer)
Glands + stroma forming nodules	Classic BPH
TWO cell layers (epithelial + basal)	BPH preserved - carcinoma LACKS basal cells

BPH histological hallmark:

Nodular hyperplasia of glands AND stroma
Glands lined by TWO layers: inner columnar secretory cells + outer basal cells
Glands may show papillary infoldings
Corpora amylacea (calcified secretions) common

Crucial distinction - BPH vs Prostate Cancer:

Feature	BPH	Prostate Adenocarcinoma
Architecture	Nodular, organized	Infiltrative, disorganized
Gland layers	Two cell layers (+ basal cells)	ONE layer (NO basal cells)
Nuclei	Normal	Large, prominent nucleoli
DRE	Smooth, enlarged, non-tender	Hard, irregular nodules
PSA	Mildly elevated	Significantly elevated
Gleason score	Not applicable	Graded 1-5
Zone	Transitional zone	Peripheral zone

The ABSENCE of basal cell layer on biopsy is the strongest histological indicator of prostate adenocarcinoma (basal cells express p63, CK5/14 - used in IHC).

BPH mechanism:

Driven by DHT (dihydrotestosterone - 5α-reductase converts testosterone to DHT in prostate)
DHT stimulates estrogen receptor-mediated stromal and glandular proliferation
Treatment: α1-blockers (tamsulosin), 5α-reductase inhibitors (finasteride), surgery (TURP)

Q87. A 40-year-old man with non-itchy rash on trunk/extremities/palms/soles, condyloma latum in perianal region. Provisional diagnosis: secondary syphilis. Most appropriate CONFIRMATORY test?

Culture of exudate
ELISA to detect antibodies
Rapid Reagin Test (RPR)
Polymerase chain reaction (PCR) ✓ (or ELISA as treponemal test)

Answer: ELISA to detect antibodies (Treponemal-specific) OR PCR

Explanation:

Syphilis serology - two types of tests:

Test Type	Examples	Detects	Use
Non-treponemal (screening)	RPR, VDRL	Anti-cardiolipin antibodies (non-specific)	Screening + monitoring treatment
Treponemal (confirmatory)	FTA-ABS, TPHA, ELISA, CLIA, MHA-TP	Anti-treponemal antibodies (specific)	CONFIRMATION

The question asks for CONFIRMATORY test:

RPR (Rapid Plasma Reagin) = SCREENING test - non-treponemal, can have false positives (SLE, pregnancy, malaria, viral infections)
For confirmation: need a treponemal-specific test:
- FTA-ABS (Fluorescent Treponemal Antibody Absorption) - gold standard confirmatory
- TPHA (Treponema pallidum Hemagglutination Assay)
- ELISA (detects IgG/IgM against T. pallidum antigens)
- PCR (detects T. pallidum DNA - highly specific)

Among the listed options:

ELISA to detect antibodies = treponemal-specific ELISA = confirmatory test ✓
PCR = also highly specific/sensitive for confirmation ✓
RPR = screening only, NOT confirmatory

Secondary syphilis features (present in this patient):

Maculopapular rash on palms and soles (pathognomonic - very few conditions cause palmar/plantar rash)
Condyloma latum (flat, moist, warty growths in moist areas = perianal, genital) - highly infectious
Generalized lymphadenopathy
Flu-like symptoms
Mucous patches (on oral mucosa)
Occurs 4-8 weeks after primary chancre

Why not culture? T. pallidum cannot be cultured in vitro on artificial media.

Q88. A 32-year-old woman with dysuria and mucopurulent genital discharge. Gonorrhea diagnosed. Which structural component of the causative organism is MOST IMPORTANT for colonization of urogenital epithelium?

Lipooligosaccharide
Major outer membrane porin proteins
Opacity proteins
Type IV pili ✓

Answer: Type IV pili

Explanation:

Neisseria gonorrhoeae virulence factors and their roles:

Virulence Factor	Role
Type IV pili	INITIAL ATTACHMENT to non-ciliated columnar epithelium
Opacity proteins (Opa)	Tighter binding after initial pili attachment + invasion
LOS (lipooligosaccharide)	Endotoxin activity, inflammation, serum resistance
Por proteins (porin, PorB)	Serum resistance, prevents phagocytic killing
IgA1 protease	Cleaves secretory IgA → evades mucosal immunity
Rmp (protein III)	Blocks bactericidal antibodies

Step-by-step colonization:

STEP 1: TYPE IV PILI → initial adherence to non-ciliated columnar epithelium
                        (urethra, cervix, fallopian tube, rectum, pharynx)
           ↓
STEP 2: OPA PROTEINS → firm adherence + facilitates invasion into epithelial cells
           ↓
STEP 3: Transcytosis through epithelial cells → submucosa
           ↓
STEP 4: LOS + complement activation → neutrophil recruitment → inflammation
           ↓
STEP 5: IgA1 protease → cleaves mucosal IgA defense

Why Type IV pili is "MOST IMPORTANT for colonization":

Pili are the first contact point between the bacterium and the host epithelium
Without pili, N. gonorrhoeae cannot attach → cannot colonize
Piliated strains are 100-1000x more virulent than non-piliated strains
Pili bind to CD46 (membrane cofactor protein) on host cells
Pili undergo antigenic variation (pilE gene rearrangement) → evades immune recognition

Why not Type IV pili vs Opacity proteins:

Opa proteins facilitate secondary/tighter binding and invasion after pili establish initial contact
Opa proteins vary (hence "opacity" - colonies appear opaque vs transparent) - important for immune evasion
But pili = initial attachment = most important for colonization

Q89. A 56-year-old woman with dyspareunia and post-coital bleeding. Cervical carcinoma associated with HPV. Most likely mechanism?

Inactivation of p53 and RB proteins ✓
Presence of abnormal number of centromeres
Virus replication in basal cells
Downregulation of TNF receptors

Answer: Inactivation of p53 and RB (tumor suppressor) proteins

Explanation:

HPV oncogenesis - mechanism leading to cervical carcinoma:

Key HPV proteins: E6 and E7 oncoproteins

HPV integrates into host genome (high-risk types: 16, 18, 31, 33, 45)
           ↓
HPV E6 protein expressed:
  → Binds and DEGRADES P53 (via ubiquitin ligase E6-AP)
  → p53 normally: DNA damage → cell cycle arrest/apoptosis
  → Loss of p53 → cells with DNA damage continue proliferating
           ↓
HPV E7 protein expressed:
  → Binds and INACTIVATES pRb (retinoblastoma protein)
  → Normally pRb binds E2F transcription factor → prevents G1→S progression
  → Loss of pRb → E2F released → uncontrolled cell proliferation (G1→S bypass)
           ↓
Combined loss of p53 + pRb:
  → Genomic instability
  → Uncontrolled proliferation
  → Accumulation of additional mutations
           ↓
CERVICAL CARCINOMA

Summary of HPV oncoproteins:

Protein	Target	Effect
E6	p53	Degradation → loss of apoptosis/cell cycle arrest
E7	pRb	Inactivation → loss of G1 checkpoint
E5	EGFR	Promotes cell growth

Why not "virus replication in basal cells"?

This describes the pathogenesis of genital warts (condyloma acuminata) caused by low-risk HPV (6, 11)
In cancer-causing infection (high-risk HPV 16, 18): viral genome INTEGRATES into host DNA (loses episomal form) → disrupts E2 (suppressor of E6/E7) → overexpression of E6/E7 → carcinogenesis
Productive viral replication (with viral particle release) occurs in the SURFACE layers, not basal cells

Why not "abnormal centromeres"?

Centrosome amplification is a consequence of carcinogenesis, not the primary HPV mechanism

Cervical carcinoma risk factors:

HPV infection (HPV 16 = squamous cell carcinoma, HPV 18 = adenocarcinoma)
Multiple sexual partners
Early sexual debut
Smoking (impairs local immune surveillance)
Immunosuppression (HIV)

Q90. A 45-year-old with Cryptococcus neoformans meningitis. Treated with amphotericin B + flucytosine. Reason for combination?

Enhances spectrum of antifungal activity
Improves drug penetration into CNS
Prevents antifungal resistance ✓
Reduces side effects of amphotericin B

Answer: Prevents antifungal resistance (+ synergistic effect)

(This is the same question as Q56 and Q59 in previous sets - confirming the same answer)

Explanation:

Amphotericin B mechanism:

Binds ergosterol in fungal cell membrane → forms pores → increased membrane permeability → ion leakage → cell death

Flucytosine (5-FC) mechanism:

Taken up by fungal cells via cytosine permease
Converted to 5-fluorouracil (5-FU) by cytosine deaminase
5-FU → inhibits thymidylate synthase → blocks DNA synthesis
Also converted to 5-fluorouridine triphosphate → inhibits RNA synthesis

Why combination works:

1. Prevents resistance to 5-FC (primary rationale):

5-FC monotherapy → resistance develops rapidly in ~40% of cases
Resistance mechanisms: mutations in cytosine permease (drug cannot enter), cytosine deaminase (cannot activate drug), or UMP pyrophosphorylase (downstream enzyme)
Amphotericin B disrupts cell membrane → enhances 5-FC uptake → prevents permease-deficient mutants from surviving → prevents resistance

2. Synergistic killing:

Ampho B-induced membrane disruption → ↑intracellular 5-FC uptake → enhanced DNA/RNA inhibition
Together: faster CSF sterilization than either drug alone

3. Both have good CNS penetration:

5-FC: excellent CSF penetration (lipophilic, small molecule, CSF/plasma ~70-80%)
Amphotericin B: adequate CNS penetration (lipid formulations better)

WHO induction regimen for cryptococcal meningitis:

2 weeks: Amphotericin B (0.7-1mg/kg/day) + Flucytosine (100mg/kg/day in 4 divided doses)
Followed by: Fluconazole consolidation → maintenance

Q91. A 30-year-old pregnant woman with BP 140/105 mmHg diagnosed with hypertension. Which antihypertensive is CONTRAINDICATED?

Enalapril ✓
Labetalol
Methyldopa
Nifedipine

Answer: Enalapril (ACE inhibitor - contraindicated in pregnancy)

Explanation:

ACE inhibitors and ARBs are ABSOLUTELY CONTRAINDICATED in pregnancy (especially 2nd and 3rd trimester):

Why Enalapril is contraindicated:

Enalapril (ACE inhibitor) → Crosses placenta
           ↓
Inhibits fetal ACE → ↓Angiotensin II in fetus
           ↓
FETAL TOXICITY (especially 2nd/3rd trimester):
  1. Fetal renal blood flow ↓ → Oligohydramnios (reduced amniotic fluid)
  2. Fetal renal tubular dysgenesis → Renal failure
  3. Skull ossification defects (calvarial hypoplasia)
  4. Limb contractures (from oligohydramnios)
  5. Pulmonary hypoplasia (from oligohydramnios - reduced fluid for lung development)
  6. IUGR (intrauterine growth restriction)
  7. Fetal/neonatal death

"ACE inhibitor fetopathy" - a well-recognized teratogenic syndrome.

Safe antihypertensive drugs in pregnancy:

Drug	Class	Safety	Notes
Methyldopa	Central alpha-2 agonist	Safe (1st choice)	Most studied, proven fetal safety, reduces CNS sympathetic outflow
Labetalol	Alpha + beta blocker	Safe	Commonly used in acute hypertension in pregnancy
Nifedipine	Ca channel blocker (DHP)	Safe	Used for acute severe hypertension + as tocolytic
Hydralazine	Vasodilator	Safe (IV use)	For hypertensive emergencies
Enalapril/ACE inhibitors	ACE inhibitor	CONTRAINDICATED	Fetal renal toxicity, oligohydramnios
ARBs (losartan)	AT1 blocker	CONTRAINDICATED	Same mechanism as ACEi
Atenolol	Beta blocker	Avoid (IUGR)

Classification of hypertension in pregnancy:

Gestational hypertension: BP ≥140/90 after 20 weeks, no proteinuria
Preeclampsia: hypertension + proteinuria (or other organ damage) after 20 weeks
Chronic hypertension: BP elevated before 20 weeks or pre-existing
This patient at 30y with BP 140/105 → likely gestational hypertension or preeclampsia

Q92. A 34-year-old woman visiting for family planning. Physician does NOT prescribe combined oral contraceptive pill (COCP). Most likely reason?

Family history of ovarian cyst
History of abortion
History of deep vein thrombosis ✓
History of irregular menses

Answer: History of deep vein thrombosis (DVT)

Explanation:

Combined OCP (estrogen + progestin) and thrombosis risk:

Estrogen component of COCP → hepatic effect → increases synthesis of clotting factors:

↑Factor VII, X, XII, fibrinogen
↑Prothrombin
↓Antithrombin III
↓Protein S → PRO-THROMBOTIC STATE

A patient with previous DVT already has:

Proven hypercoagulable state
Possibly underlying thrombophilia (Factor V Leiden, Prothrombin gene mutation, antiphospholipid syndrome)
High risk of recurrent DVT, pulmonary embolism (fatal)

Adding COCP estrogen → dramatically increases thrombotic risk → contraindicated

Absolute contraindications to COCP (WHO Category 4 - risk unacceptable):

Contraindication	Reason
DVT/PE (current or history)	Thrombotic risk
Stroke, ischemic heart disease	Arterial thrombosis risk
Migraine with aura	Stroke risk
Hypertension >160/100	Cardiovascular risk
Smoking + age >35	Thrombotic/cardiovascular risk
Breast cancer	Hormone-sensitive tumor
Liver disease (active)	Hepatic metabolism impaired
Pregnancy	Teratogenic risk
Breastfeeding <6 weeks	Estrogen suppresses lactation
Systemic lupus with antiphospholipid antibodies	Thrombosis risk

Why not other options?

Family history of ovarian cyst: NOT a contraindication - COCPs actually PROTECT against ovarian cysts
History of abortion: NOT a contraindication to COCP
Irregular menses: COCP is actually USED TO TREAT irregular menses (regulates cycle)

Q93. A 41-year-old woman with ER-positive invasive breast carcinoma on long-term tamoxifen. Most likely side effect?

Deep vein thrombosis
Oligomenorrhea
Pulmonary embolism
Uterine cancer ✓

Answer: Uterine cancer (Endometrial carcinoma)

Explanation:

Tamoxifen - SERM (Selective Estrogen Receptor Modulator):

Tissue	Tamoxifen Effect	Consequence
Breast	Antagonist (blocks ER)	Treats/prevents breast cancer
Uterus/Endometrium	AGONIST (activates ER)	Endometrial hyperplasia → ENDOMETRIAL CARCINOMA
Bone	Agonist	Beneficial (prevents osteoporosis)
Liver	Agonist	↑Triglycerides, ↑clotting factors
Cardiovascular	Agonist	Reduced LDL

Tamoxifen and uterine cancer:

Long-term tamoxifen (>2 years) → 2-3x increased risk of endometrial carcinoma
Risk is dose- and duration-dependent
Endometrial surveillance recommended for women on tamoxifen who develop post-menopausal bleeding
Annual gynecological examination recommended

Why uterine cancer is the MOST LIKELY side effect in this question:

The question specifically asks about LONG-TERM medication side effects
DVT and PE are known tamoxifen side effects (due to estrogen-agonist effect on liver → ↑clotting factors) but are less common with long-term use compared to the well-established endometrial cancer risk
Uterine cancer is the most concerning and clinically significant long-term complication

Tamoxifen side effects summary:

Side Effect	Mechanism
Endometrial carcinoma	Uterine ER agonism → endometrial stimulation
Hot flashes	Anti-estrogenic effect (most common symptom)
DVT/PE	↑Clotting factors (hepatic ER agonism)
Ocular toxicity (retinopathy)	Direct retinal effect
Liver toxicity	Rare
Vaginal dryness/discharge	Anti-estrogenic in vaginal epithelium

Note: Aromatase inhibitors (anastrozole, letrozole) are preferred over tamoxifen in post-menopausal women BECAUSE they do NOT have the uterotrophic side effect.

Q94. A 45-year-old man with seizures. MRI shows 3 cm right parietal mass. Histology: sheets of cells with ROUND NUCLEI, "fried egg" appearance, chicken-wire vasculature, calcification. CNS neoplasm?

Ependymoma
Glioblastoma
Meningioma
Oligodendroglioma ✓

Answer: Oligodendroglioma

Explanation:

Pathognomonic histological features of Oligodendroglioma - ALL present in this question:

Feature	Description	Significance
"Fried egg" appearance	Round nuclei with clear perinuclear halo (artifact of formalin fixation → cytoplasm shrinks away from nucleus)	PATHOGNOMONIC of oligodendroglioma
"Chicken-wire" vasculature	Thin-walled branching capillaries surrounding tumor cells	Classic vascular pattern
Calcifications	Stippled calcifications on imaging and histology	Very common (~70-90% of oligodendrogliomas)
Sheets of uniform cells	Monomorphic population	Typical

Oligodendroglioma:

Grade II (WHO) - slow-growing; Grade III = anaplastic oligodendroglioma
Arises from oligodendrocytes (myelin-forming cells of CNS)
Location: cerebral hemispheres (frontal lobe most common) → explains seizures
Molecular signature: 1p/19q co-deletion (chromosome 1p and 19q deletions) - diagnostic AND associated with better prognosis
IDH mutation (IDH1/IDH2) - almost always present

CNS tumor histological comparison:

Tumor	Key Histology	Location
Oligodendroglioma	Fried egg cells, chicken-wire, calcification	Cerebral hemispheres
Glioblastoma (GBM)	Necrosis with pseudopalisading, microvascular proliferation	Cerebral hemispheres
Meningioma	Psammoma bodies (calcification), whorls, syncytial pattern	Meninges (extraaxial)
Ependymoma	Perivascular pseudorosettes, ependymal rosettes	Ventricles/spinal cord
Astrocytoma	Glial fibrillary acidic protein (GFAP)+, variable morphology	Cerebral hemispheres
Schwannoma	Antoni A/B, Verocay bodies	Nerve roots, CPA

Treatment: Surgery + chemotherapy (PCV: procarbazine, lomustine/CCNU, vincristine) + radiotherapy. Oligodendrogliomas with 1p/19q co-deletion are chemosensitive - better prognosis than astrocytomas.

Q95. Researchers study hypertensive intracerebral hemorrhage over 10 years. Which brain location is MOST COMMON for this condition?

Basal ganglia ✓
Cerebellum
Cerebral hemisphere
Pons

Answer: Basal ganglia (specifically putamen)

Explanation:

Hypertensive intracerebral hemorrhage - location by frequency:

Location	Frequency	Notes
Basal ganglia (putamen)	~35-50% (MOST COMMON)	Classic hypertensive hemorrhage
Thalamus	~15-25%
Pons	~10-15%	Devastating, high mortality
Cerebellum	~10%	Surgical emergency (decompress)
Cerebral lobes (white matter)	~10-15%	Consider other causes (CAA, AVM)

Why basal ganglia is most common:

The putamen and thalamus (parts of basal ganglia) are supplied by lenticulostriate arteries (deep penetrating branches of MCA)
These are small-caliber, high-pressure vessels with thin walls
Chronic hypertension → lipohyalinosis (hyaline degeneration + fibrosis) of vessel walls + Charcot-Bouchard microaneurysms
Microaneurysm rupture → hemorrhage into basal ganglia
This is called "small vessel disease" or "hypertensive arteriopathy"

Charcot-Bouchard microaneurysms:

Form in small penetrating arteries (100-300μm diameter) in basal ganglia and pons
From chronic hypertension → focal vessel wall weakness
Classic cause of hypertensive hemorrhage

Clinical features of putaminal hemorrhage:

Contralateral hemiplegia + hemisensory loss
Eyes deviate TOWARD the lesion (away from hemiplegia)
If large: herniation, coma, death

Cerebellar hemorrhage - though less common, surgically important because posterior fossa expansion can compress the brainstem → rapid deterioration; evacuation can be life-saving.

Q96. A 35-year-old woman with headache, vomiting, blurred vision. CT shows intracranial mass + hydrocephalus with DILATED LATERAL AND 3rd VENTRICLES but NORMAL 4th VENTRICLE. Type of hydrocephalus?

Communicating
Ex-vacuo
Non-communicating ✓
Normal pressure hydrocephalus

Answer: Non-communicating (Obstructive) Hydrocephalus

Explanation:

The anatomy is the KEY diagnostic clue:

LATERAL VENTRICLES (dilated) → 3rd VENTRICLE (dilated) → [BLOCKED HERE]
                                                           ↓
                                               CEREBRAL AQUEDUCT (of Sylvius)
                                               [OBSTRUCTION at or above aqueduct]
                                                           ↓
                                               4th VENTRICLE (NORMAL size)

Dilated lateral + 3rd ventricles + NORMAL 4th ventricle = obstruction at the CEREBRAL AQUEDUCT (Aqueductal stenosis) OR between 3rd ventricle and 4th ventricle

Non-communicating hydrocephalus = obstruction WITHIN the ventricular system:

CSF cannot flow from ventricles to subarachnoid space
Blockage points and resulting dilation:
- Foramen of Monro blockage → unilateral/bilateral lateral ventricle dilation
- Cerebral aqueduct (Sylvius) blockage → lateral + 3rd ventricle dilation, NORMAL 4th (as in this case)
- 4th ventricle foramina (Magendie, Luschka) → all ventricles dilated

Hydrocephalus classification:

Type	Mechanism	Pattern
Non-communicating (obstructive)	Blockage within ventricular system	Selective ventricular dilation proximal to block
Communicating	Blockage in subarachnoid space or impaired absorption	ALL ventricles dilated equally
Ex-vacuo	Brain atrophy → ventricles expand to fill space	Ventricles enlarged but ICP normal, sulci enlarged too
Normal pressure hydrocephalus (NPH)	Impaired CSF absorption	All ventricles enlarged, normal ICP, triad: dementia + gait + urinary incontinence

This patient: The mass (likely at aqueductal level or 3rd ventricle) blocks CSF flow → backs up into 3rd ventricle and lateral ventricles → non-communicating hydrocephalus

Why communicating is wrong: In communicating hydrocephalus (e.g., post-meningitis, post-SAH), ALL ventricles including the 4th would be dilated.

Q97. A 72-year-old man with forgetfulness and inability to perform daily activities. Diagnosed with Alzheimer's disease dementia. Which neuronal protein accumulation is present?

Alpha-synuclein in basal ganglia
Aβ amyloid plaques in neocortex ✓
Huntingtin in the caudate nucleus
Ubiquitin in frontal and temporal lobes

Answer: Aβ amyloid plaques in neocortex

Explanation:

Alzheimer's disease - neuropathological hallmarks:

Finding	Protein	Location	Significance
Senile (amyloid/neuritic) plaques	Aβ amyloid (beta-amyloid)	Neocortex, hippocampus	EXTRACELLULAR, diagnostic
Neurofibrillary tangles (NFTs)	Hyperphosphorylated tau	Neurons (intracellular)	Correlates with dementia severity
Amyloid angiopathy	Aβ in vessel walls	Cerebral blood vessels	Predisposes to lobar hemorrhage

Amyloid cascade hypothesis:

APP (amyloid precursor protein) gene → overexpression or mutation
           ↓
Abnormal cleavage by β-secretase (BACE) + γ-secretase
           ↓
Aβ42 peptide (amyloidogenic, insoluble)
           ↓
Aggregates → oligomers → fibrils → AMYLOID PLAQUES (extracellular)
           ↓
Neuroinflammation + Tau phosphorylation → TANGLES
           ↓
Synaptic loss → neuronal death → dementia

Protein accumulation by neurodegenerative disease:

Disease	Protein	Location
Alzheimer's	Aβ amyloid + tau	Neocortex, hippocampus
Parkinson's	Alpha-synuclein (Lewy bodies)	Substantia nigra, basal ganglia
Huntington's	Huntingtin	Striatum (caudate nucleus + putamen)
Frontotemporal dementia	TDP-43 or FUS or tau	Frontal + temporal lobes
ALS	TDP-43, SOD1	Motor neurons
CJD (Prion)	PrPSc	Cortex (spongiform changes)

Why not alpha-synuclein in basal ganglia? That is Parkinson's disease (Lewy bodies in substantia nigra → dopamine depletion → movement disorder)

Why not huntingtin in caudate nucleus? That is Huntington's disease (chorea, psychiatric symptoms, striatal atrophy)

Q98. A 28-year-old man with acute neurological signs, 2 months post-stray dog bite (forearm, skin break, tissue damage). Rabies suspected. Most SPECIFIC laboratory method to detect the causative agent?

CSF profiling
Detection of anti-rabies IgM
Detection of Negri bodies
Detection of viral antigen ✓ (Direct Fluorescent Antibody test - DFA)

Answer: Detection of viral antigen (DFA - Direct Fluorescent Antibody test)

Explanation:

Rabies diagnosis - available tests:

Test	Specimen	Sensitivity	Specificity	Notes
DFA (Direct Fluorescent Antibody) - viral antigen	Brain biopsy (gold standard), skin biopsy (nape of neck), corneal impression	Very high	Very high	Most specific ante-mortem and post-mortem test
RT-PCR	Saliva, CSF, skin	Very high	Very high	Detects viral RNA
Negri bodies (H&E histology)	Brain tissue	~80%	High	Classic but less sensitive than DFA
Virus isolation (cell culture)	CSF, saliva	Variable	High	Reference labs only, slow
Serology (IgM/IgG)	Serum, CSF	Variable	Moderate	Less useful if not vaccinated (may not develop antibodies early enough)
CSF profile	CSF	Non-specific	Non-specific	Shows lymphocytic pleocytosis - not specific

Why DFA (viral antigen detection) is MOST SPECIFIC:

Uses fluorescent-labeled anti-rabies antibodies to detect rabies virus nucleocapsid antigen in tissue
Gold standard diagnostic test (WHO/CDC recommended)
Can be done on:
- Brain tissue (post-mortem - most sensitive)
- Skin biopsy (nape of neck - hair follicle nerve endings - ante-mortem)
- Corneal impression smear (ante-mortem)
- Saliva/mucosa

Negri bodies:

Eosinophilic cytoplasmic inclusions in neurons (especially hippocampal Purkinje cells, cerebellum)
Contain viral ribonucleoprotein
Sensitivity ~80% - DFA is more sensitive and specific
On H&E stain: pathognomonic when present, but absence does NOT rule out rabies

Among the listed options: "Detection of viral antigen" = DFA test = most specific ✓

Q99. A 5-year-old boy with high fever, headache, vomiting for 2 days, temperature 40°C, positive Babinski's test. CSF: Neisseria meningitidis. Which virulence factor is most important for SURVIVAL IN BLOODSTREAM?

Capsule ✓
Opacity proteins
Pili
Protease

Answer: Capsule

Explanation:

Neisseria meningitidis virulence factors:

Virulence Factor	Function
Polysaccharide capsule	SURVIVAL IN BLOODSTREAM - resists complement + phagocytosis
Pili (type IV)	Attachment to nasopharyngeal epithelium (initial colonization)
Opacity proteins (Opa, Opc)	Adhesion to and invasion of epithelial and endothelial cells
LOS (lipooligosaccharide)	Endotoxin → septic shock, DIC
IgA1 protease	Cleaves secretory IgA → evades mucosal immunity
Factor H binding protein	Binds complement regulator factor H → inhibits alternative complement pathway
NadA (adhesin)	Additional adhesion

Why CAPSULE is the key virulence factor for bloodstream survival:

N. meningitidis enters bloodstream (meningococcemia)
           ↓
Host defense: COMPLEMENT SYSTEM (opsonization + membrane attack complex)
           + PHAGOCYTES (neutrophils, macrophages)
           ↓
CAPSULE provides resistance to BOTH:
  1. ANTI-PHAGOCYTIC: capsule prevents opsonization (blocks C3b deposition)
                      and inhibits phagocytosis by neutrophils
  2. SERUM RESISTANCE: capsule blocks complement membrane attack complex (MAC)
                       from reaching outer membrane
           ↓
Bacteria SURVIVE in bloodstream → high-grade bacteremia
           ↓
Cross blood-brain barrier → MENINGITIS

N. meningitidis serogroups and their capsules:

Serogroup	Capsule type	Epidemiology
A	Polysaccharide	Africa (meningitis belt), epidemics
B	Polysaccharide	UK, Europe (capsule poorly immunogenic - molecular mimicry with brain)
C	Polysaccharide	Common globally
W135	Polysaccharide	Hajj pilgrims
Y	Polysaccharide	USA

Vaccines target the capsular polysaccharide (except group B - poorly immunogenic):

Meningococcal conjugate vaccines (MCV4): covers A, C, W, Y
MenB vaccine (Bexsero, Trumenba): protein-based (factor H binding protein, etc.)

Babinski's sign positive in this child = upper motor neuron sign = meningeal irritation/brain involvement (encephalitis component or raised ICP causing cortical signs)

Summary Table - Q81 to Q99

Q	Answer	Core Concept
81	Reduces glomerular blood flow	NSAIDs block prostaglandins → afferent arteriole constricts → ↓GFR
82	Suppresses T-lymphocytes	MCD = T-cell disorder; prednisolone suppresses T-cells → removes permeability factor
83	Endometrial glands and stroma	Endometriosis diagnosis requires BOTH glands AND stroma ectopically
84	Chronic anovulation	PCOS → no dominant follicle → no progesterone → no menstruation
85	Lobular carcinoma	Single-file pattern + absent E-cadherin + ER/PR+ = ILC
86	Benign prostatic hyperplasia	Two cell layers (basal preserved) + nodules + smooth DRE = BPH
87	ELISA (treponemal antibody)	Confirmatory = treponemal-specific; RPR = screening only
88	Type IV pili	Initial attachment to urogenital epithelium = pili; opa = secondary binding
89	Inactivation of p53 and RB	HPV E6 degrades p53; HPV E7 inactivates pRb → uncontrolled proliferation
90	Prevents antifungal resistance	5-FC monotherapy → rapid resistance; Ampho B prevents this + synergy
91	Enalapril	ACE inhibitors → fetal renal toxicity, oligohydramnios → absolutely contraindicated
92	History of DVT	COCP estrogen → pro-thrombotic → absolute contraindication with DVT history
93	Uterine cancer	Tamoxifen = uterine ER agonist → endometrial hyperplasia → carcinoma (long-term)
94	Oligodendroglioma	Fried egg cells + chicken-wire vasculature + calcification = pathognomonic
95	Basal ganglia	Putamen most common site; lenticulostriate arteries → Charcot-Bouchard aneurysms
96	Non-communicating hydrocephalus	Dilated lateral + 3rd, normal 4th = aqueductal obstruction = non-communicating
97	Aβ amyloid plaques in neocortex	Alzheimer's = Aβ (extracellular) + tau tangles; alpha-syn = Parkinson's
98	Detection of viral antigen (DFA)	DFA on skin/brain = gold standard; Negri bodies less sensitive
99	Capsule	Anti-phagocytic + anti-complement = bloodstream survival; pili = initial attachment

100. A 42-year-old man presents to the clinic with sudden onset of headache, fever, vomiting, myalgia and photophobia. On examination, his temperature is 38°C and neck stiffness is observed with meningeal signs. A diagnosis of meningitis is made. Cerebrospinal Fluid ( CSF ) examination results are as follows: TEST PATIENT'S RESULT REFERENCE RANGE WBC count 800cells/Cu.mm 0- 5 cells/Cu.mm Type of cells Neutrophils 96% Lymphocytes 4% 0 - 5 lymphocytes/Cu.mm Protein 110 mg/aL 15-50 mg/dL Glucose 40 - 75 ma/dL 35 mg/dL Turbid Appearance Clear Which of the following infections is the most likely diagnosis in this case? A. Fungal meningitis B. Pyogenic meningitis C. Tubercular meningitis D. Viral meningitis 101. A 56-year-old schizophrenia patient has been on haloperidol treatment for the past 6 months. Following the development of extrapyramidal side effects, the psychiatrist decides to change medication to olanzapine. Which of the following actions of olanzapine best explains the rationale for choosing it? A. It has less affinity for GABA receptors. B. It has a higher affinity for serotonin receptors C. It has less affinity for dopamine D2 receptors D. It has higher antagonism at muscarinic receptors 102. A 32-year-old man with an inguinal hernia undergoes an elective surgery. Just before surgery, the anaesthetist administers atropine injection as a routine pre-anaesthetic medication. Which of the following effects is most beneficial for the patient by the administration of this drug? A. It decreases exocrine gland secretion. B. It decreases gastrointestinal motility. C. It increases heart rate. D. It relaxes bronchial smooth muscle. 103. A 36-year-old drug addict is brought to the Emergency Department in an unresponsive state with pinpoint pupils and shallow respirations. He is suspected of opioid overdose and was immediately given intravenous naloxone. Which of the following indications best explains the effects of the above drug in this case? A. To reverse sedation B. To reduce pain C. To treat opioid addiction D. To reverse respiratory depression 104. A 14-year-old boy with a history of seizures is under treatment with carbamazepine. Recently, he was diagnosed with pulmonary tuberculosis and started on rifampicin. On follow-up, the patient's father complains of increased frequency of seizures, despite drug compliance. The physician suspects rifampicin-induced drug interaction. Which of the following mechanisms best explains the above drug interaction? A. Rifampicin antagonizes the effects of carbamazepine. B. Rifampicin enhances the excretion of carbamazepine C. Rifampicin increases the metabolism of carbamazepine. D. Rifampicin prevents absorption of carbamazepine. 105. A 24-year-old man presents with a five-month history of worsening headaches and progressive coarseness of facial features. He is suspected to have acromegaly. Initial investigation shows a high baseline random growth hormone level. Which of the following tests can be performed to further support the diagnosis? A. Dexamethasone suppression test B. Glucose tolerance test C. Insulin tolerance test D. Water deprivation test 106. A 37-year-old woman presents with a tingling sensation in the perioral region. Physical examination reveals positive Chvostek sign and Trousseau sign indicative of tetany. One month ago, she underwent thyroid surgery to remove a thyroid nodule. Which of the following electrolyte abnormalities is most likely to be present in this patient? A. Hypercalcaemia B. Hyperkalaemia C. Hypocalcaemia D. Hypokalaemia 107. A 28-year-old woman is admitted to hospital with meningococcal meningitis. She develops altered mental status, hypotension and ecchymoses over her upper and lower limbs. Laboratory investigations reveal features of adrenal failure and Disseminated Intravascular Coagulation (DIC). Which of the following pathological changes in the adrenal glands is most likely leading to adrenal failure in this patient? A. Cortical atrophy B. Fibrosis C. Haemorrhagic necrosis D. Inflammatory oedema 108. A 20-year-old man with diabetes mellitus is brought to the Emergency Department in a comatose state. Laboratory investigations show blood glucose of 32 mol/L (Reference range <7.8mol/L), urine ketone 4+ and presence of metabolic acidosis. Which of the following hormonal changes best describes the pathogenesis of diabetes mellitus in this patient? A. Absolute decrease in insulin B. Decrease insulin glucagon ratio C. Increase in glucagon D. Insulin resistance 109. A 37-year-old woman complains of heat intolerance, irritability and excessive sweating for the last six months. Physical Examination reveals bilateral exophthalmos. Clinical Diagnosis of Graves' disease is made. Which of the following lab-diagnosis findings is most consistent with the above diagnosis of the patient? A. High Thyroid Stimulating Hormone (TSH), decrease in free Thyroxine (T4) B. High TSH, d e c r e a s e in free Triiodothyronine (T3) C. Low TSH, increase in free T4 D. Low TSH, decrease in free T4 110. A 40-year-old diabetic patient is treated for an infected wound on the right foot. A culture of pus from the wound grows gram-negative bacilli with bluish-green colonies on nutrient agar. Which of the following organisms is most likely the causative agent in this case? A. Aeromonas hydrophila B. Enterobacter cloacae C. Escherichia coli D. Pseudomonas aeruginosa 11. A 42-year-old woman presents to the clinic with insomnia, irritability and tremor for two months. After investigation, she is diagnosed with hyperthyroidism and prescribed carbimazole. Which of the following processes in thyroid hormone synthesis is initially inhibited by the prescribed drug? A. iodide trapping B. Lodination C. Peroxidation D. Proteolysis 112. A 62-year-old postmenopausal woman is treated for osteoporosis with oral alendronate. She is advised to take the drug on an empty stomach with water and sit upright for at least 30 minutes. Which of the following reasons best explains the above advice? A. To help complete absorption of the drug. B. To increase the bioavailability of the drug. C. To prevent gastric erosive effects of the drug. D. To prevent reflux of gastric contents. 113. Over The past five years, Malaysia has seen an increase in a large number of people who have BMI higher than the recommended average. The rise of obesity over this short period of time in a large number of people in a given population is a public health concern. Which of the following rate of spreads best fits the above scenario? A. Endemic B. Epidemic C. Pandemic D. Sporadic 114. The high mortality rate for Non-Communicable Diseases (NCDs) is causing an increased concern globally. Crucial (prevention strategies include lifestyle management and health promotion. Which of the following level of prevention best fits the above statement? A. Primary B. Primordial C. Secondary D. Tertiary 115. A 56-year-old male comes for his routine health screening. The doctor makes a diagnosis of metabolic syndrome and explains the related health risks to him. Which of the following health risks is most likely associated with the above syndrome? A. Cancer B. Gout C. Heart diseases D. Stomach ulcer 116. A 3-year-old boy is diagnosed with leukaemia. Currently, he is on immunosuppressive chemotherapy Which of the following vaccines would be contraindicated to the boy? A. Diphtheria vaccine B. Hepatitis vaccine C. Mumps vaccine D. Tetanus vaccine 117. A home care nurse routinely assesses the nutritional status of her malnourished patient. Which of the following (nutritional assessments are best done to monitor the patient with the above condition? A. Anthropometry B. Biochemical examination C. Clinical examination D. Dietary assessment 118. A 35-year-old married man has recently diagnosed with HIV infection. The consultant recommends some measures to prevent the transmission of HIV to his wife. Which of the following preventive measures is most effective for the above scenario? A. Barrier method B. Health education C. Practice monogamy D. Sexual abstinence 119. Familial Hypercholesterolaemia (FH) is a common inherited disorder that remains undetected in the general population. Screening interventions have been designed to identify the disorder so that earlier management can be instituted. Which of the following screening interventions would be the most appropriate to be carried out? A. Case-finding B. Mass screening C. Multiphasic screening D. Opportunistic screening 120. Mosquito-borne diseases are posing significant global health burdens. In recent years, the use of pathogen-blocking Wolbachia bacteria has shown a substantial reduction in dengue transmission. Which of the following methods best fits the description in the above scenario? A. Biological Control B. Biotechnology C. Engineering control D. Genetic technology

Here are all 21 questions (Q100-Q120) answered fully:

Q100. A 42-year-old man with sudden headache, fever, vomiting, myalgia, photophobia, neck stiffness. CSF: WBC 800 cells/mm³ (96% neutrophils), protein 110mg/dL, glucose 35mg/dL, turbid. Most likely diagnosis?

Fungal meningitis
Pyogenic meningitis ✓
Tubercular meningitis
Viral meningitis

Answer: Pyogenic meningitis (Bacterial meningitis)

Explanation:

CSF analysis - the diagnostic key:

CSF Parameter	This Patient	Pyogenic (Bacterial)	Viral	TB/Fungal
Appearance	Turbid	Turbid/purulent	Clear	Clear/slightly turbid
WBC count	800 cells/mm³	>100-50,000	10-500	10-500
Cell type	96% Neutrophils	Predominantly PMNs	Lymphocytes	Lymphocytes
Protein	110 mg/dL (HIGH)	High (>100mg/dL)	Normal/mildly raised	Markedly elevated
Glucose	35 mg/dL (LOW)	<40mg/dL (<50% serum)	Normal	Very low
Opening pressure	High	Very high	Normal/mildly high	High

Interpreting this CSF:

Turbid: pus (neutrophils + bacteria) = bacterial infection
Neutrophil predominance (96%): hallmark of acute bacterial (pyogenic) meningitis
High protein: BBB breakdown + cellular exudate
Low glucose (35 mg/dL): bacteria consume glucose + impaired transport = hypoglycorrhachia (CSF:serum glucose <0.6)

Common bacterial causes by age:

Age	Common organisms
Neonates (0-3 months)	Group B Streptococcus, E. coli, Listeria
Children (3m - 18y)	N. meningitidis, S. pneumoniae
Adults (18-50y)	S. pneumoniae, N. meningitidis
Elderly (>50y)	S. pneumoniae, Listeria, Gram-negative bacilli

Treatment: Empirical IV ceftriaxone + dexamethasone (reduces inflammation, prevents deafness)

Clinical signs present:

Neck stiffness: meningism from meningeal irritation
Photophobia + headache + fever: classic meningitis triad
Kernig's sign (knee cannot be extended when hip flexed) and Brudzinski's sign (neck flexion → involuntary hip flexion)

Q101. A 56-year-old schizophrenic on haloperidol develops extrapyramidal side effects. Switched to olanzapine. Which action of olanzapine explains the rationale?

Less affinity for GABA receptors
Higher affinity for serotonin receptors
Less affinity for dopamine D2 receptors ✓
Higher antagonism at muscarinic receptors

Answer: Less affinity for dopamine D2 receptors

Explanation:

This is the same fundamental concept as the clozapine question (Q8, Q33) - applied to olanzapine.

Extrapyramidal Side Effects (EPS) from haloperidol:

Haloperidol (typical antipsychotic) = high D2 receptor affinity in ALL dopaminergic pathways:
- Mesolimbic (therapeutic - reduces psychosis)
- Nigrostriatal (causes EPS - Parkinsonism, akathisia, dystonia, tardive dyskinesia)
- Mesocortical (negative symptoms worsened)
- Tuberoinfundibular (hyperprolactinemia)

Olanzapine (atypical/second-generation antipsychotic):

Property	Haloperidol (typical)	Olanzapine (atypical)
D2 affinity	Very high (>80% occupancy)	Lower (~60-70% occupancy)
D2 striatal binding	Tight, slow dissociation	Loose, fast dissociation
5-HT2A affinity	Low	High (5-HT2A blockade)
EPS risk	High	Low
Tardive dyskinesia	High	Low

Why lower D2 affinity = fewer EPS:

Low nigrostriatal D2 blockade → insufficient to cause supersensitivity or EPS
Additionally: 5-HT2A blockade → enhances dopamine release in striatum (compensates for D2 blockade) → further reduces EPS

Olanzapine receptor profile: D1, D2, D4, 5-HT2A, 5-HT2C, H1, M1-M5, α1 antagonist

Olanzapine side effects:

Metabolic syndrome: weight gain, dyslipidemia, hyperglycemia (most significant concern)
Sedation (H1 blockade)
Anticholinergic effects (muscarinic blockade)
Hyperprolactinemia (less than haloperidol)
Low EPS risk

Q102. A 32-year-old man undergoing elective inguinal hernia surgery. Atropine given as pre-anaesthetic medication. Most BENEFICIAL effect for this patient?

It decreases exocrine gland secretion ✓
It decreases GI motility
It increases heart rate
It relaxes bronchial smooth muscle

Answer: It decreases exocrine gland secretion

Explanation:

Atropine = competitive muscarinic (M) receptor antagonist (anticholinergic)

Why atropine is given as pre-anaesthetic (pre-operative) medication:

The PRIMARY reason for pre-operative atropine is to: Reduce airway secretions (salivary and bronchial gland secretions)

During anaesthesia/surgery:
Tracheal intubation + surgical stimulation → reflex secretions
Inhaled anaesthetics (older agents: ether, halothane) → trigger salivation/bronchospasm
           ↓
Excess secretions in airway → aspiration → pneumonia
           ↓
ATROPINE blocks muscarinic M3 receptors on glands
           ↓
Reduced salivation, reduced bronchial secretions, reduced gastric secretions
           ↓
DRY SURGICAL FIELD + REDUCED ASPIRATION RISK

Atropine effects from muscarinic blockade:

Effect	Mechanism	Clinical Use
↓Exocrine gland secretions	M3 block on salivary, lacrimal, bronchial glands	Pre-op: most beneficial - dry field
↓GI motility	M3 block on gut	Not main reason for pre-op use
↑Heart rate	M2 block on SA node	Treats bradycardia, blocks vagal reflexes during surgery
Bronchodilation	M3 block on bronchial smooth muscle	Useful but not primary pre-op reason
Mydriasis	M3 block on iris	Eye exams
↓Bladder tone	M3 block	Urinary retention risk

Why "decreases exocrine gland secretion" is the BEST answer for pre-anaesthetic use:

The most critical concern during general anaesthesia is airway management
Excessive saliva + bronchial secretions → aspiration pneumonia, laryngospasm, difficult intubation
Atropine ("drying agent") ensures a dry airway - this is the primary pre-operative benefit

Note: Modern anaesthesia with non-irritant volatile agents (sevoflurane, desflurane) has reduced routine atropine pre-medication, but it remains in use for specific indications.

Q103. A 36-year-old drug addict in Emergency with unresponsive state, pinpoint pupils, shallow respirations. Suspected opioid overdose. Given IV naloxone. Best explanation for its use?

To reverse sedation
To reduce pain
To treat opioid addiction
To reverse respiratory depression ✓

Answer: To reverse respiratory depression

Explanation:

Opioid overdose triad (present in this patient):

Pinpoint pupils (miosis) - opioid stimulation of Edinger-Westphal nucleus
Respiratory depression (shallow respirations, low RR) - opioid action on brainstem respiratory centers
CNS depression/coma (unresponsive state)

Why respiratory depression is the PRIMARY indication for naloxone:

Opioids (heroin, morphine, fentanyl) →
Bind mu (μ) opioid receptors in brainstem respiratory centers
           ↓
↓Respiratory rate and ↓tidal volume
           ↓
RESPIRATORY DEPRESSION → Hypoxia + Hypercapnia
           ↓
Respiratory ARREST → DEATH (if untreated)

Naloxone mechanism:

Pure opioid receptor antagonist (no intrinsic activity)
Competitively displaces opioids from μ, κ, δ receptors
Rapidly reverses respiratory depression (most dangerous complication)
Also reverses sedation, miosis, and analgesia
IV/IM/intranasal; onset: 2-5 minutes IV; duration: 30-90 minutes (shorter than most opioids → may need repeat dosing or infusion)

Why "reverse respiratory depression" is the BEST answer (not "reverse sedation"):

Both sedation and respiratory depression are reversed
However, the life-threatening indication = respiratory depression
Respiratory arrest = immediate death - this is what naloxone saves the patient from
Sedation reversal is secondary benefit
"Reverse respiratory depression" specifically addresses the immediate life-threatening cause of the emergency presentation

Naloxone uses:

Opioid overdose reversal (emergency)
Naloxone + opioid combinations (e.g., buprenorphine/naloxone = Suboxone) for addiction treatment - but naloxone alone does NOT treat addiction
Reversal of post-operative opioid respiratory depression

Q104. A 14-year-old with seizures on carbamazepine. Now started on rifampicin for TB. Increased seizure frequency despite compliance. Mechanism of drug interaction?

Rifampicin antagonizes carbamazepine
Rifampicin enhances carbamazepine excretion
Rifampicin increases the metabolism of carbamazepine ✓
Rifampicin prevents absorption of carbamazepine

Answer: Rifampicin increases the metabolism of carbamazepine (CYP450 induction)

Explanation:

Rifampicin = most potent CYP450 enzyme INDUCER in clinical use

Rifampicin administration
           ↓
Induces hepatic CYP450 enzymes (especially CYP3A4, CYP2C9, CYP2C19)
           ↓
INCREASED METABOLISM of carbamazepine (substrate of CYP3A4)
           ↓
Carbamazepine is broken down FASTER
           ↓
DECREASED PLASMA LEVELS of carbamazepine
           ↓
Sub-therapeutic carbamazepine → Loss of seizure control
           ↓
INCREASED SEIZURE FREQUENCY despite drug compliance

Key pharmacokinetic concepts:

Concept	Rifampicin Effect
CYP induction	Increases enzyme amount/activity
Effect on substrate drugs	DECREASED plasma levels
Clinical consequence	Loss of therapeutic effect
Onset	3-10 days after starting rifampicin
Offset	2-4 weeks after stopping rifampicin

Drugs whose efficacy is REDUCED by rifampicin (CYP induction):

Anticonvulsants: carbamazepine, phenytoin, valproate
Oral contraceptive pills → contraceptive failure (very important clinically)
Antiretrovirals: protease inhibitors
Warfarin → INR falls, need higher doses
Corticosteroids → reduced effect
Cyclosporine → transplant rejection risk
Methadone → withdrawal symptoms

Carbamazepine note: Carbamazepine ITSELF is also a CYP inducer (auto-induction) - but in this question, rifampicin induces additional CYP3A4 → further accelerates carbamazepine breakdown.

Management: Increase carbamazepine dose with careful monitoring of plasma levels when rifampicin is co-administered.

Q105. A 24-year-old man with worsening headaches and coarsening facial features. Suspected acromegaly. High baseline random GH level. Which test FURTHER SUPPORTS the diagnosis?

Dexamethasone suppression test
Glucose tolerance test ✓
Insulin tolerance test
Water deprivation test

Answer: Oral Glucose Tolerance Test (OGTT)

Explanation:

Acromegaly diagnosis - why OGTT?

Normal physiology:

Oral glucose load → hyperglycemia → somatostatin release → SUPPRESSES GH to <1 ng/mL

In acromegaly:

GH is secreted autonomously by a pituitary GH-secreting adenoma (somatotropinoma)
GH secretion is NOT suppressible by glucose
OGTT with 75g glucose → GH FAILS TO SUPPRESS (remains >1 ng/mL) or paradoxically rises

OGTT test for acromegaly:
Give 75g oral glucose
Measure GH at 0, 30, 60, 90, 120 minutes
           ↓
NORMAL: GH suppressed to <1 ng/mL (or <0.4 ng/mL with sensitive assay)
           ↓
ACROMEGALY: GH NOT suppressed (remains >1 ng/mL or paradoxically increases)

This is the GOLD STANDARD confirmatory test for acromegaly.

Other tests for acromegaly:

IGF-1 (insulin-like growth factor 1): elevated in acromegaly (GH → liver → IGF-1 production). Best SCREENING test - single measurement, reflects 24h GH exposure
MRI pituitary: locates the adenoma
Visual field testing (bitemporal hemianopia from chiasmal compression)

Why not the other tests?

Dexamethasone suppression test: used for Cushing's syndrome (cortisol hypersecretion, not GH)
Insulin tolerance test: used to STIMULATE GH and cortisol (for GH deficiency or adrenal insufficiency diagnosis)
Water deprivation test: used for diabetes insipidus diagnosis

Clinical features of acromegaly:

Coarsening of facial features: enlarged nose, lips, jaw (prognathism)
Macroglossia, widely spaced teeth
Enlarged hands and feet (rings/shoes no longer fit)
Frontal bossing, supraorbital ridge enlargement
Soft tissue swelling (carpal tunnel syndrome)
Headache (from pituitary adenoma expansion)
Visual field defects (bitemporal hemianopia)
Hypertension, diabetes (GH is counter-regulatory)

Q106. A 37-year-old woman with perioral tingling, positive Chvostek sign, positive Trousseau sign. Had thyroid surgery 1 month ago. Most likely electrolyte abnormality?

Hypercalcemia
Hyperkalemia
Hypocalcemia ✓
Hypokalemia

Answer: Hypocalcemia

Explanation:

Classic post-thyroidectomy complication: Hypoparathyroidism → Hypocalcemia

Thyroid surgery (thyroidectomy or excision of thyroid nodule)
           ↓
ACCIDENTAL REMOVAL OR DEVASCULARIZATION of PARATHYROID GLANDS
(4 parathyroid glands embedded in thyroid tissue - easily injured/removed)
           ↓
↓PTH secretion → HYPOPARATHYROIDISM
           ↓
↓Calcium reabsorption from bone
↓Calcium reabsorption from kidney (↓tubular reabsorption)
↓Activation of Vitamin D (PTH normally stimulates 1α-hydroxylase)
           ↓
HYPOCALCEMIA

Signs of hypocalcemia present in this patient:

Sign	Mechanism	Test
Chvostek sign	Tapping facial nerve → ipsilateral facial muscle twitch	Tap anterior to tragus → watch corner of mouth twitch
Trousseau sign	Inflate BP cuff above systolic for 3 min → carpal spasm (main d'accoucheur)	Obstructive ischemia → hyperexcitable neuromuscular junction
Perioral tingling	Sensory nerve hyperexcitability	Perioral paresthesia
Tetany	Spontaneous muscle cramps	-

Why hypocalcemia causes neuromuscular irritability:

Ca²⁺ stabilizes nerve cell membranes (blocks Na⁺ channels)
↓Ca²⁺ → threshold potential easier to reach → spontaneous action potentials → tetany

Other signs/symptoms of hypocalcemia:

Muscle cramps, tetany
Seizures (severe)
Prolonged QT interval on ECG → arrhythmias
Laryngospasm (life-threatening)
Anxiety, depression
Dry skin, brittle nails, cataracts (chronic)

Treatment: IV calcium gluconate (acute/symptomatic) → oral calcium + vitamin D (maintenance)

Q107. A 28-year-old woman with meningococcal meningitis develops altered mental status, hypotension, ecchymoses, adrenal failure, and DIC. What pathological change in adrenal glands causes adrenal failure?

Cortical atrophy
Fibrosis
Haemorrhagic necrosis ✓
Inflammatory edema

Answer: Haemorrhagic necrosis (Waterhouse-Friderichsen Syndrome)

Explanation:

Waterhouse-Friderichsen Syndrome (WFS):

Bilateral adrenal hemorrhagic necrosis complicating overwhelming septicemia
Most commonly caused by Neisseria meningitidis (meningococcemia)
Also: S. pneumoniae, H. influenzae, Pseudomonas (rarer)

Pathogenesis:

Neisseria meningitidis septicemia
           ↓
LOS (endotoxin) → massive cytokine release (IL-1, TNF, IL-6)
           ↓
SEPTIC SHOCK → DIC (disseminated intravascular coagulation)
           ↓
DIC → fibrin thrombi in adrenal sinusoids + hemorrhage
           ↓
BILATERAL ADRENAL HEMORRHAGIC NECROSIS
           ↓
Destruction of adrenal cortex → NO cortisol, NO aldosterone
           ↓
ACUTE ADRENAL INSUFFICIENCY (adrenal crisis)
  - Hypotension (no vasopressor response, no aldosterone)
  - Hyponatremia + Hyperkalemia
  - Refractory shock → death

Clinical features present in this patient:

Altered mental status: cerebral hypoperfusion + meningitis
Hypotension: adrenal crisis + septic shock
Ecchymoses/purpura: DIC + meningococcal endotoxin-mediated vasculitis (purpura fulminans)
Adrenal failure: bilateral adrenal hemorrhagic necrosis
DIC: fibrin thrombi + consumption of clotting factors

Gross pathology of Waterhouse-Friderichsen:

Adrenal glands: enlarged, hemorrhagic, dark red/black
Bilateral involvement
Complete cortical destruction

Distinguishing from Addison's disease:

Addison's = chronic, autoimmune cortical atrophy/destruction (90% due to autoimmune)
WFS = acute, hemorrhagic necrosis from meningococcemia

Q108. A 20-year-old man in coma. Blood glucose 32 mmol/L (very high), urine ketones 4+, metabolic acidosis. Which hormonal change describes the pathogenesis?

Absolute decrease in insulin ✓
Decreased insulin:glucagon ratio
Increase in glucagon
Insulin resistance

Answer: Absolute decrease in insulin (Type 1 DM - Diabetic Ketoacidosis)

Explanation:

Key clues: Young patient + hyperglycemia + ketonuria 4+ + metabolic acidosis = Diabetic Ketoacidosis (DKA)

DKA = complication of TYPE 1 DIABETES MELLITUS

Type 1 DM pathogenesis:

Autoimmune destruction of pancreatic β-cells
T-cell mediated destruction (CD8+ cytotoxic T cells, CD4+ helper T cells)
Autoantibodies: anti-GAD (glutamic acid decarboxylase), anti-islet cell, anti-insulin
Result: ABSOLUTE deficiency of insulin (no β-cells left to produce insulin)

DKA mechanism:

ABSOLUTE insulin deficiency (Type 1 DM) + trigger (infection, non-compliance)
           ↓
↑Glucagon (unopposed - no insulin)
           ↓
LIVER:
  Glycogenolysis + Gluconeogenesis → ↑BLOOD GLUCOSE → HYPERGLYCEMIA
  Lipolysis activated → Free fatty acids → KETOGENESIS
  Fatty acids → Acetyl CoA → Ketone bodies (acetoacetate, β-hydroxybutyrate, acetone)
           ↓
Osmotic diuresis (glucose > renal threshold → glucosuria → polyuria → dehydration)
Ketoacids accumulate → METABOLIC ACIDOSIS (anion gap)
           ↓
Coma, Kussmaul breathing (deep rapid - compensatory hyperventilation)

Why "absolute decrease in insulin" is the BEST answer:

This patient is a 20-year-old (young) with:
- Very high glucose (32 mmol/L)
- Ketonuria 4+ (heavy ketosis = absolute insulin deficiency allowing uncontrolled lipolysis)
- Metabolic acidosis
This profile = Type 1 DM with DKA = ABSOLUTE insulin deficiency

Compare with Type 2 DM:

Insulin resistance = Type 2 DM (usually older, obese, no ketosis)
Type 2: relative insulin deficiency + resistance; ketosis uncommon (residual insulin suppresses ketogenesis)

Why not "decreased insulin:glucagon ratio"?

This describes the combined pathophysiology (true but less specific)
The fundamental defect in Type 1 is absolute insulin deficiency

DKA treatment: IV fluids, IV insulin infusion, potassium replacement, bicarbonate (if severe), treat precipitant

Q109. A 37-year-old woman with heat intolerance, irritability, excessive sweating, bilateral exophthalmos. Diagnosed with Graves' disease. Most consistent lab finding?

High TSH, decreased free T4
High TSH, decreased free T3
Low TSH, increased free T4 ✓
Low TSH, decreased free T4

Answer: Low TSH, increased free T4

Explanation:

Graves' disease = autoimmune hyperthyroidism

Pathogenesis:

B cells produce TSH RECEPTOR ANTIBODIES (TRAb/TSI - thyroid-stimulating immunoglobulins)
           ↓
TRAb binds and ACTIVATES TSH receptor on thyroid follicular cells
(mimics TSH action - but WITHOUT normal negative feedback control)
           ↓
Continuous thyroid stimulation:
  → Thyroid hyperplasia (diffuse goiter)
  → EXCESS T3 and T4 production
           ↓
High T3/T4 → negative feedback on HYPOTHALAMUS and PITUITARY
           ↓
↓TRH → ↓TSH (pituitary SUPPRESSED by excess thyroid hormones)
           ↓
LOW TSH + HIGH FREE T4 (and HIGH FREE T3)

Lab pattern in hyperthyroidism:

Condition	TSH	Free T4	Free T3
Hyperthyroidism (Graves')	↓ (suppressed)	↑	↑
Hypothyroidism (primary)	↑	↓	↓
Secondary hypothyroidism	↓	↓	↓
Subclinical hyperthyroidism	↓	Normal	Normal
Subclinical hypothyroidism	↑	Normal	Normal

Graves' disease specific features:

Bilateral exophthalmos (proptosis): TRAb activates orbital fibroblasts → glycosaminoglycan deposition + edema + fat accumulation in retro-orbital space → eyes protrude (this is PATHOGNOMONIC of Graves' among hyperthyroid conditions)
Pretibial myxedema: skin thickening on shins
Thyroid bruit (hypervascular gland)
Diffuse goiter

Symptoms explained by excess T3/T4:

Heat intolerance (↑basal metabolic rate)
Excessive sweating (↑peripheral vasodilation)
Irritability/anxiety/tremor (↑adrenergic activity)
Tachycardia, palpitations
Weight loss despite increased appetite

Q110. A 40-year-old diabetic with infected foot wound. Pus culture grows Gram-negative bacilli with BLUISH-GREEN colonies on nutrient agar. Causative organism?

Aeromonas hydrophila
Enterobacter cloacae
Escherichia coli
Pseudomonas aeruginosa ✓

Answer: Pseudomonas aeruginosa

Explanation:

Bluish-green colonies = Pseudomonas aeruginosa - this is pathognomonic.

Pseudomonas aeruginosa distinctive pigments:

Pigment	Color	Property
Pyocyanin	Blue-green/bluish	Water-soluble, diffuses into agar, unique to P. aeruginosa
Pyoverdine (fluorescein)	Yellow-green, fluorescent	Siderophore (iron chelation)
Pyorubin	Red-brown	Some strains
Pyomelanin	Dark brown	Some strains

The blue-green color of colonies = pyocyanin + pyoverdine combination

Other Pseudomonas characteristics:

Gram-negative, non-fermentative bacillus (oxidase-positive)
Obligate aerobe (non-fermenter on MacConkey = colorless)
Grape-like/fruity odor (ammonia + 2-aminoacetophenone)
Produces biofilm (important for chronic infections)
Multi-drug resistant (intrinsic + acquired resistance)
Grows in minimal nutrient environments

Why diabetic patients are particularly susceptible:

Diabetic foot = compromised vascular supply + neuropathy + impaired immunity
Hyperglycemia → impairs neutrophil function
P. aeruginosa is an opportunistic pathogen - exploits the immunocompromised state

Pseudomonas virulence factors:

Exotoxin A: inhibits protein synthesis (like diphtheria toxin - ADP-ribosylates EF-2)
Elastase (LasB): destroys elastin in blood vessel walls
Alginate (biofilm): resists antibiotics and phagocytosis
LPS: endotoxin, inflammatory
Type III secretion system: injects toxins into cells (ExoS, ExoT, ExoU)

Treatment: Antipseudomonal agents: piperacillin-tazobactam, ceftazidime, cefepime, carbapenems (imipenem, meropenem), ciprofloxacin, aminoglycosides (combination therapy preferred)

Q111. A 42-year-old woman with insomnia, irritability, tremor diagnosed with hyperthyroidism. Prescribed carbimazole. Which thyroid hormone synthesis step is INITIALLY inhibited?

Iodide trapping
Iodination ✓ (organification)
Peroxidation
Proteolysis

Answer: Iodination (Organification) - via inhibition of Thyroid Peroxidase (TPO)

Explanation:

Thyroid hormone synthesis steps:

STEP 1: IODIDE TRAPPING
Na/I symporter (NIS) transports I⁻ into follicular cell
[NOT inhibited by carbimazole]

STEP 2: PEROXIDATION (Oxidation)
Thyroid peroxidase (TPO) oxidizes I⁻ → I₂ (active iodine)
[INITIALLY INHIBITED by carbimazole]

STEP 3: IODINATION (Organification)
TPO iodinates tyrosine residues on thyroglobulin
MIT (monoiodotyrosine) and DIT (diiodotyrosine) formed
[ALSO INHIBITED by carbimazole - same enzyme: TPO]

STEP 4: COUPLING
TPO couples MIT + DIT → T3 (triiodothyronine)
       DIT + DIT → T4 (thyroxine)
[INHIBITED by carbimazole - same TPO enzyme]

STEP 5: STORAGE
Thyroid hormone stored as thyroglobulin in follicles

STEP 6: PROTEOLYSIS
Lysosomal proteases cleave thyroglobulin → release T3/T4
[NOT inhibited by carbimazole]

Carbimazole (and propylthiouracil - PTU) mechanism:

Both are thionamides
Block thyroid peroxidase (TPO)
TPO is required for BOTH peroxidation (step 2) AND organification/iodination (step 3) AND coupling (step 4)
The FIRST/INITIAL step inhibited = peroxidation (step 2, which prevents all subsequent steps)

The question asks for the INITIAL step inhibited:

Organification/Iodination is the step where TPO iodinates thyroglobulin
This is classically described as the initial blocked step in most pharmacology texts
Without iodination, no MIT/DIT → no T3/T4

Additional property of PTU (not carbimazole):

PTU also inhibits peripheral T4 → T3 conversion (blocks deiodinase type 1) → useful in thyroid storm
Carbimazole: does NOT inhibit peripheral conversion

Clinical note: Carbimazole is a prodrug → converted to methimazole in the body.

Side effects of thionamides:

Agranulocytosis (serious, 0.5%) - stop drug immediately if fever/sore throat → urgent CBC
Rash, urticaria
Arthralgia
Hepatotoxicity (PTU > carbimazole)

Q112. A 62-year-old postmenopausal woman on oral alendronate for osteoporosis. Advised to take on empty stomach with water, sit upright for 30 minutes. Best reason?

To help complete absorption of the drug
To increase bioavailability of the drug
To prevent gastric erosive effects of the drug ✓
To prevent reflux of gastric contents

Answer: To prevent gastric/esophageal erosive effects (esophagitis)

Explanation:

Alendronate = oral bisphosphonate (nitrogen-containing) for osteoporosis

Why these specific instructions exist:

The main adverse effect of oral bisphosphonates = ESOPHAGEAL IRRITATION/EROSION:

Alendronate is a HIGHLY CAUSTIC drug to mucosa (very acidic)
           ↓
If tablet remains in esophagus (e.g., taken lying down, taken with small amount of water)
           ↓
Drug dissolves against esophageal mucosa → DIRECT CAUSTIC INJURY
           ↓
ESOPHAGITIS → ESOPHAGEAL ULCERS → ESOPHAGEAL STRICTURE
(very painful, can be severe/life-threatening)

Why each instruction:

Instruction	Reason
Empty stomach	Food/milk significantly reduces absorption (bisphosphonates bind calcium → food chelates drug)
Full glass of water (250mL)	Dilutes the drug, washes it quickly into stomach away from esophagus
Sit or stand upright for 30 min	GRAVITY ensures drug rapidly passes through esophagus → prevents drug from pooling/sitting against esophageal wall
Do not lie down	Lying down → drug refluxes back into esophagus → mucosal contact → erosion

Primary reason = prevent esophageal erosion (the most clinically significant risk)

Why not "increase bioavailability"?

Alendronate oral bioavailability is already very low (~0.7%) regardless of these instructions
These instructions do NOT increase bioavailability significantly
The purpose is SAFETY (prevent mucosal damage), not pharmacokinetic optimization

Other bisphosphonate side effects:

GI upset, nausea (common)
Osteonecrosis of the jaw (ONJ) - rare, after dental procedures, more with IV bisphosphonates
Atypical femoral fracture (subtrochanteric/diaphyseal) - with long-term use (>5 years)
Hypocalcemia
Renal impairment (IV bisphosphonates especially)

Q113. Malaysia sees a large increase in obesity (high BMI) over 5 years in a large number of people. This rate of spread best fits which term?

Endemic
Epidemic ✓
Pandemic
Sporadic

Answer: Epidemic

Explanation:

Epidemiological terms for disease/condition spread:

Term	Definition	Example
Endemic	Constant, baseline level of a disease WITHIN a specific geographical area	Malaria in Sub-Saharan Africa
Epidemic	Occurrence of cases of disease in excess of normal expectancy in a community/region over a defined period	Dengue outbreak in Malaysia; Obesity surge in Malaysia over 5 years
Pandemic	Epidemic that spreads across multiple countries/continents	COVID-19, 1918 influenza
Sporadic	Occurs occasionally, irregularly, without specific pattern	Rabies cases in Malaysia
Outbreak	Localized epidemic (same as epidemic but smaller geographic area)	Food poisoning at a restaurant

Why "Epidemic" fits this scenario:

Large number of people affected (exceeds normal expectation)
Specific geographical area (Malaysia)
Defined time period (5 years)
Rapid increase (unusual rise above baseline)

Obesity as an epidemic is well-recognized - the WHO describes a "global obesity epidemic" as epidemic applies to any health condition (not just infectious disease).

Why not Pandemic?

Pandemic requires spread across multiple countries/continents - this question specifies Malaysia only

Why not Endemic?

Endemic implies a constant, expected baseline rate - this describes a NEW, RAPIDLY RISING surge above what was expected

Q114. High NCD mortality globally. Prevention strategies include lifestyle management and health promotion. Which level of prevention?

Primary ✓
Primordial
Secondary
Tertiary

Answer: Primary Prevention

Explanation:

Levels of Prevention:

Level	Definition	Target	NCD Examples
Primordial	Prevent CONDITIONS that give rise to risk factors	Population level, social/environmental determinants	Policies against unhealthy food marketing, urban planning for physical activity
Primary	Prevent disease from occurring in susceptible individuals	At-risk individuals	Health promotion, lifestyle modification, vaccination
Secondary	Early detection and prompt treatment to halt/slow disease progression	People with early disease (asymptomatic)	Screening (mammogram, Pap smear, blood pressure screening)
Tertiary	Reduce impact of established disease, prevent complications, rehabilitation	People with established disease	Cardiac rehabilitation, diabetes management programs

Why the answer is Primary Prevention:

"Lifestyle management and health promotion" = modifying risk factors BEFORE disease occurs
Target: people who don't yet have NCDs but are at risk
Strategies: diet modification, exercise promotion, smoking cessation, alcohol reduction
Aim: PREVENT the occurrence of NCDs (cardiovascular disease, diabetes, cancer, COPD)

Why not Primordial?

Primordial = structural/policy level (e.g., government food regulations, creating safe spaces for exercise, laws against tobacco advertising) - addressing the conditions that allow risk factors to develop

Why not Secondary?

Secondary = screening for early disease (e.g., blood sugar screening for pre-diabetes)

Why not Tertiary?

Tertiary = managing existing disease (e.g., cardiac rehab after MI)

Q115. A 56-year-old man diagnosed with metabolic syndrome. Which health risk is MOST LIKELY associated?

Cancer
Gout
Heart diseases ✓
Stomach ulcer

Answer: Heart diseases (Cardiovascular disease)

Explanation:

Metabolic Syndrome (IDF/WHO/NCEP-ATP III criteria): A cluster of metabolic abnormalities that dramatically increase cardiovascular risk:

Diagnostic criteria (3 or more of 5):

Central obesity (waist circumference: >90cm males, >80cm females - Asian criteria)
Elevated triglycerides (≥1.7 mmol/L or on treatment)
Reduced HDL (<1.0 mmol/L males, <1.3 mmol/L females)
Elevated blood pressure (≥130/85 mmHg or on treatment)
Elevated fasting glucose (≥5.6 mmol/L or on treatment for Type 2 DM)

Primary health risks of metabolic syndrome:

Risk	Magnitude
Cardiovascular disease (CHD, stroke)	2-3x increased risk = PRIMARY risk
Type 2 Diabetes Mellitus	5x increased risk
Non-alcoholic fatty liver disease	Common
Obstructive sleep apnea	Associated

Why cardiovascular disease is the primary concern:

Each component of metabolic syndrome independently increases cardiovascular risk
Combined: multiplicative risk increase
The syndrome was originally defined to identify people at high cardiovascular risk
Insulin resistance → endothelial dysfunction → atherosclerosis → coronary artery disease → myocardial infarction, stroke

Why not gout?

Gout (hyperuricemia) can be associated with metabolic syndrome but is NOT the primary defining health risk

Why not cancer?

Metabolic syndrome/obesity does increase some cancers (colorectal, endometrial, breast) but cardiovascular disease remains the dominant associated risk

Q116. A 3-year-old boy with leukemia on immunosuppressive chemotherapy. Which vaccine is CONTRAINDICATED?

Diphtheria vaccine
Hepatitis vaccine
Mumps vaccine ✓
Tetanus vaccine

Answer: Mumps vaccine (MMR - live attenuated)

(Same question as Q35 - confirming the same answer)

Explanation:

Mumps vaccine = part of MMR (Measles-Mumps-Rubella) = LIVE ATTENUATED vaccine

Live vaccines absolutely contraindicated in immunocompromised patients:

The attenuated pathogen can cause vaccine-strain disseminated disease in the absence of a competent immune system
A child with leukemia on chemotherapy has severely impaired cellular immunity
MMR given to such a patient → could cause vaccine-strain measles encephalitis, disseminated infection, or death

Vaccine safety summary:

Vaccine	Type	Safe in Immunocompromised?
Mumps (MMR)	Live attenuated	CONTRAINDICATED
Tetanus	Toxoid	Safe
Diphtheria	Toxoid	Safe
Hepatitis B	Recombinant subunit	Safe
Hepatitis A	Inactivated	Safe
IPV (injected polio)	Inactivated	Safe

Q117. A home care nurse routinely assesses nutritional status of a malnourished patient. Which nutritional assessment is BEST for monitoring?

Anthropometry ✓
Biochemical examination
Clinical examination
Dietary assessment

Answer: Anthropometry

Explanation:

For MONITORING (tracking changes over time), anthropometry is superior:

Method	Best For	Monitoring?
Anthropometry	Serial measurement of physical dimensions	BEST for monitoring - objective, quantitative, serial
Biochemical	Metabolic status, visceral protein	Supplements anthropometry; affected by non-nutritional factors
Clinical	Signs of malnutrition (late signs)	Subjective, detects late-stage changes
Dietary	Intake assessment	Detects deficiencies before clinical signs; retrospective

Why anthropometry is BEST for monitoring:

Objective: uses standardized measurements (weight, height, MUAC)
Quantitative: numbers can be tracked (e.g., weight gain from 4.75→6.28 kg = 32% gain)
Reproducible: same results if technique is standardized
Sensitive to change: small changes detected quickly
Non-invasive, cheap, field-applicable
Serial tracking: trends over time clearly documented (weight gain/loss curves)

Key anthropometric measurements for monitoring malnutrition recovery:

Weight: simplest, most sensitive change indicator
MUAC (mid-upper arm circumference): rapid field assessment in emergencies
Weight-for-height: wasting (acute malnutrition)
Height-for-age: stunting (chronic malnutrition)

Biochemical tests (albumin, prealbumin, transferrin) reflect metabolic status but:

Albumin has a long half-life (20 days) → slow to change → poor for short-term monitoring
Affected by inflammation, liver disease, kidney disease (non-nutritional)
More expensive, requires lab facilities

Q118. A 35-year-old married man recently diagnosed with HIV. Consultant recommends measures to prevent transmission to his wife. Most EFFECTIVE preventive measure?

Barrier method
Health education
Practice monogamy
Sexual abstinence ✓ (but practically, barrier method)

Answer: Sexual abstinence (most effective theoretically) / Barrier method (most practical)

Explanation:

HIV transmission prevention - effectiveness hierarchy:

Preventive Measure	Efficacy	Notes
Sexual abstinence	100%	No sexual contact = zero transmission risk
Barrier method (male condom, consistently/correctly used)	~85-95%	Most practical effective method
Pre-Exposure Prophylaxis (PrEP)	~99%	For HIV-negative partner
Treatment as Prevention (TasP)	~96%	If HIV+ partner has undetectable viral load
Post-Exposure Prophylaxis (PEP)	~80-85%	Within 72h of exposure
Practice monogamy	Reduces NEW partners, not existing transmission	Doesn't prevent transmission to existing partner
Health education	Enables informed decisions	Indirect, foundational

For the specific scenario (HIV+ husband → protect HIV- wife):

Sexual abstinence = theoretically 100% effective (no contact = no transmission)
Barrier method (condoms) = most practical and commonly recommended
Among the options, sexual abstinence gives 100% protection

Modern HIV prevention (ABC approach):

Abstinence (most effective)
Be faithful / Be monogamous (reduce partners)
Condoms (consistent and correct use)
Plus: PrEP, TasP, PEP

Clinical note: With modern antiretroviral therapy (ART), an HIV+ person with an undetectable viral load has effectively zero risk of transmitting HIV sexually (U=U: Undetectable = Untransmittable). This is now a cornerstone of HIV prevention but was not an option listed here.

Q119. Familial Hypercholesterolaemia (FH) is a common inherited disorder, undetected in general population. Screening interventions to identify it. Most APPROPRIATE screening?

Case-finding ✓
Mass screening
Multiphasic screening
Opportunistic screening

Answer: Case-finding (Cascade screening)

Explanation:

Familial Hypercholesterolaemia (FH):

Autosomal dominant condition (LDLR, APOB, PCSK9 mutations)
Very high LDL cholesterol from birth → premature atherosclerosis
Prevalence: heterozygous FH ~1:250-500 (common but underdiagnosed)
Cascade screening = once index case identified, screen ALL first-degree relatives

Screening methods comparison:

Type	Definition	Best For
Case-finding (Cascade screening)	Screening relatives (first-degree) of a KNOWN case	Inherited conditions with high familial risk - BEST for FH
Mass screening	Screening the entire population regardless of risk	High-prevalence conditions (e.g., BP screening)
Opportunistic screening	Screening during routine clinical encounters	Hypertension, diabetes - picked up at regular visits
Multiphasic screening	Multiple different screening tests in one session	Health fairs - broad screening for multiple conditions
Selective/targeted screening	Screening high-risk groups	Breast cancer (age ≥50), cervical cancer

Why case-finding/cascade screening is BEST for FH:

FH is inherited → relatives have 50% chance of having the condition (autosomal dominant)
Most cost-effective strategy: identify 1 index case → screen ALL first-degree relatives (parents, siblings, children)
Each positive case identified → screen THEIR relatives → "cascade" effect
3-fold higher yield compared to general population screening
Endorsed by: WHO, NICE, ESC/EAS FH Guidelines

Cascade screening protocol:

Identify index case (proband) via clinical diagnosis or opportunistic detection
Screen all first-degree relatives (lipid profile + genetic testing)
Positive relatives → screen their first-degree relatives
Continue until cascade exhausted

Q120. Mosquito-borne diseases - Use of Wolbachia bacteria in mosquitoes shows substantial reduction in dengue transmission. Which method best fits this description?

Biological Control ✓
Biotechnology
Engineering control
Genetic technology

Answer: Biological Control

Explanation:

Wolbachia bacteria for dengue control:

Wolbachia are naturally occurring intracellular bacteria found in ~60% of insect species
When introduced into Aedes aegypti mosquitoes (dengue vector):
- Blocks dengue virus replication inside the mosquito
- Reduces mosquito lifespan
- Reduces mosquito egg production (cytoplasmic incompatibility)
- Spreads through mosquito populations (maternally transmitted)
Result: Dengue transmission dramatically reduced

Why this is BIOLOGICAL CONTROL:

Biological control = the use of living organisms (natural enemies, parasites, pathogens) to control pest populations or interrupt disease transmission

Wolbachia = a LIVING MICROORGANISM (bacterium)
           ↓
Used to control ANOTHER LIVING ORGANISM (Aedes mosquito)
           ↓
Which controls DISEASE TRANSMISSION (dengue)
           ↓
= BIOLOGICAL CONTROL

Vector control method comparison:

Method	Examples	Category
Biological control	Wolbachia in mosquitoes, Bacillus thuringiensis (Bti) larvae-killing bacteria, sterile insect technique, natural predators (copepods, fish)	Uses living organisms
Engineering control	Draining stagnant water, proper waste management, window screens, bed nets, air conditioning	Physical/structural measures
Chemical control	Insecticides (DDT, malathion), larvicides (temephos)	Chemical agents
Genetic technology	Release of Insects with Dominant Lethality (RIDL), gene drive technology	Genetic modification of organism
Biotechnology	Recombinant vaccines, genetically engineered products	Gene-level manipulation

Why not genetic technology?

Genetic technology would involve directly modifying the genome of the mosquito (e.g., CRISPR gene drive)
Wolbachia is a natural bacterium introduced into mosquitoes - no genetic modification of the mosquito itself occurs

Real-world success: The World Mosquito Program (WMP) has deployed Wolbachia-carrying Aedes aegypti in multiple countries, showing 77% reduction in dengue incidence in Yogyakarta, Indonesia (2021, NEJM).

Summary Table - Q100 to Q120

Q	Answer	Core Concept
100	Pyogenic meningitis	Turbid CSF + neutrophils + high protein + low glucose = bacterial
101	Less affinity for D2 receptors	Atypical antipsychotics (olanzapine) = lower striatal D2 binding = less EPS
102	Decreases exocrine gland secretion	Pre-op atropine = dry airway (prevents aspiration from secretions)
103	Reverse respiratory depression	Opioid overdose → respiratory arrest is life-threatening; naloxone reverses it
104	Increases metabolism of carbamazepine	Rifampicin = potent CYP inducer → ↑CZP breakdown → subtherapeutic levels
105	Glucose tolerance test	OGTT: GH fails to suppress in acromegaly = gold standard confirmatory test
106	Hypocalcemia	Post-thyroidectomy → parathyroid injury → ↓PTH → ↓Ca²⁺ → tetany
107	Haemorrhagic necrosis	Waterhouse-Friderichsen: meningococcemia → DIC → bilateral adrenal hemorrhage
108	Absolute decrease in insulin	Young + DKA (glucose + ketones + acidosis) = Type 1 DM = absolute insulin deficiency
109	Low TSH, increased free T4	Graves': TRAb stimulates thyroid → excess T4/T3 → suppresses TSH
110	Pseudomonas aeruginosa	Bluish-green (pyocyanin) colonies = P. aeruginosa
111	Iodination (organification)	Carbimazole blocks TPO → initial inhibition of organification
112	Prevent gastric erosive effects	Alendronate = caustic; upright posture + water → drug quickly leaves esophagus
113	Epidemic	Large numbers, specific area (Malaysia), defined time (5 years), above expected = epidemic
114	Primary prevention	Lifestyle management + health promotion = prevent disease before it occurs
115	Heart diseases	Metabolic syndrome → 2-3x cardiovascular risk = primary associated risk
116	Mumps vaccine	Live attenuated MMR → contraindicated in immunocompromised
117	Anthropometry	Objective, quantitative, serial weight/measurement tracking = best monitoring tool
118	Sexual abstinence	100% effective; condom = most practical; abstinence = most effective theoretically
119	Case-finding (cascade)	FH = autosomal dominant; screen relatives of index cases = cascade/case-finding
120	Biological control	Wolbachia = living organism used to control another organism (mosquito) = biological control

61. A 45-year-old man presents with progressive difficulty in swallowing solids and liquids, regurgitates undigested food and feelings of heartburn for the past 6 months. Upper GI endoscopy and esophageal manometry reveal esophageal aperistalsis, incomplete lower esophageal sphincter (LES) relaxation and increased LES tone. Which of the following conditions is the most likely diagnosis? A. Achalasia B. Hiatal hernia C. Oesophageal atresia D. Reflux oesophagitis 62. A 20-year-old man presents with intermittent attacks of relatively mild diarrhoea, fever and abdominal pain for the past 4 months. Following an endoscopic biopsy, he is diagnosed with Crohn disease. Which of the following morphological features is most likely to be seen in his intestines? A. Cobblestone appearance of mucosa B. Diffuse lesions in the colon and rectum C. Inflammation limited to mucosa and submucosa D. Superficial broad-based colonic ulcers 63. A 60-year-Old man, a chronic alcoholic presents to the Emergency Department with confusion and lethargy. On examination, he is drowsy and jaundiced. He has ascites, flapping tremors, and palmar erythema. A clinical diagnosis of hepatic encephalopathy due ot alcoholic liver disease is made. Which of the following mechanisms is the most likely cause of palmar erythema in this patient? A. Coagulopathy leading to bleeding B. Elevated serum ammonia C. Hyperestrogenemia causing local vasodilatation D. Portosystemic shunts reversing blood flow 64. A 40-year-old woman presents with episodes of watery diarrhoea, bloating and flatulence for the past one year. She has been feeling tired and weak. Her duodenal biopsy reveals characteristic features of Coeliac disease. Which of the following abnormalities is the most likely cause of malabsorption in this patient? A. Defect in transepithelial lipoprotein transport B. Disaccharidase deficiency in brush border cells C. Inadequate luminal hydration D. Intestinal immune reaction to gluten 65. A group of 16 college students present to the Emergency Department with complaints of fever and bloody diarrhoea following the consumption of hamburgers. Two students have low platelet counts and signs of renal failure. Based on the laboratory investigations food associated infection is confirmed. Which of the following pathotypes of the causative organism is the most likely cause of this infection? A. Enterotoxigenic Escherichia coli B. Enterohaemorrhagic Escherichia coli C. Enteropathogenic Escherichia coli D. Enteroaggregative Escherichia coli 66. A 30-year-old man presents to the clinic with complaints of abdominal pain and bloody diarrhoea for three days. Stool examination shows leukocytes, erythrocytes and spiral-shaped bacteria. A diagnosis of Campylobacter gastroenteritis is made. Which of the following virulence factors of the causative organism plays an important role in inducing inflammation in this patient? A. Capsule B. Cytolethal toxin C. Fimbriae D. Flagella 67. A family of four presents to the clinic with abdominal cramps,diarrhea, nausea and vomiting after about 5 hours following consumption of cheeseburger and pastries at a party. Investigations confirm Staphylococcal food poisoning. Which of the following virulence factors is the most likely cause for the above condition? A. Emetic toxin B. Enterotoxin C. Toxic shock toxin D. Verotoxin 68. A 38-year-old man presents to the clinic with several episodes of watery diarrhoea and severe dehydration of 2 days duration. Based on laboratory investigations a diagnosis of Cholera is made. Which of the following pathogenic mechanisms best describes the above clinical condition? A. Action of adenyl cyclase cyclic AMP on enterocytes B. Destruction of colonic villi by enterotoxin C. Invasion of enterocytes by cytotoxin D. Verotoxin action on colonic epithelial cells 69. A 28-year-old farmer presents to the clinic with abdominal pain and bloody diarrhoea. On examination, he appears pale. Stool examination reveals the presence of Ancylostoma duodenale eggs. Which of the following mechanisms best explains the pathogenesis for the bloody diarrhoea? A. Rupture of capillaries in the mucosa layer of the small intestine. B. Attachment of adult parasites to the mucosa of the small intestine. C. Migration of the larvae damages the intestinal mucosa. D. Intestinal inflammation caused by eosinophilia. 70. A 34-year-old man presents to the clinic with acute onset of high-grade fever and pain in the right hypochondrium of 2 days duration. He gives a history of recurrent bloody diarrhoea 2 months ago for which he did not receive any treatment. Investigations confirm a diagnosis of amoebic liver abscess. Which of the following infective forms of the causative organism is most likely associated with the above condition? A. Oocyst B. Trophozoites C. Tachyzoites D. Sporozoites 71. A 65-year-old man presents with loss of weight, haemoptysis and passing blood in stool for the past 1 month. He is diagnosed with gastrointestinal stromal cell tumor and is treated with imatinib mesylate oral tablet. Which of the following mechanisms best describes the action of the above drug? A. Inhibition of proteasome B. Inhibition of epidermal growth factor C. Inhibition of topoisomerase I D. Inhibition of tyrosine kinase 72. A 43-year-old man, who is on treatment for intestinal amoebiasis with metronidazole consumes alcohol at a party. He complains of specific adverse effects. The physician suspects alcohol-induced drug interaction. Which of the following adverse effects is most likely to have occurred in the above patient? A. Diarrhoea B. Disulfiram reaction C. Metallic taste D. Numbness 73. A3-year-old boy is brought to the clinic with complaints of fever, diarrhoea and dehydration. He is diagnosed with infective gastroenteritis. The mother admits that she has given the boy loperamide which was earlier prescribed to his elder sister who has a similar problem. However, the Paediatrician advice to give only symptomatic treatment instead of continuing with loperamide. Which of the following conditions is most likely prevented by withdrawing the drug? A. Intestinal perforation B. Paralytic ileus C. Systemic spread of infection D. Toxic megacolon 74. A 39-year-old man presents with heartburn and loss of appetite for the past 1 week. He gives the history of skipping meals. He is diagnosed with acute gastritis and is treated with omeprazole. Which of the following mechanisms best describes the action of the above drug? A. It blocks H2receptor B. It blocks M1 receptor C. It inhibits H+K+ATPase D. It neutralizes gastric acid 75. A 4-year-old boy is brought to the Paediatrician with complaints of facial puffiness, abdominal distension and pedal oedema for the past one week. Laboratory investigations reveal massive proteinuria. He is diagnosed with nephrotic syndrome. The child is given a course of steroids and he responds well to the treatment. Which of the following conditions is the most likely cause of nephrotic syndrome in this patient? A. Focal segmental glomerulosclerosis B. Membranoproliferative glomerulonephritis C. Membranous nephropathy D. Minimal change disease 76. A 75-year-old man, a heavy smoker presents with haematuria, fatigue and loss of weight for the past 1 month. Radiological studies show a mass in the upper pole of his right kidney with metastases to the lung. An ultrasound-guided biopsy from the renal mass reveals rounded to polygonal-shaped cells with an abundant clear cytoplasm. Which of the following neoplasms is most likely to be present in this patient? A. Angiomyolipoma B. Clear cell carcinoma C. Oncocytoma D. Papillary renal cell carcinoma 77. A 54-year-old woman complains of severe headache and dizziness. She has a history of recurrent urinary tract infection. Her blood pressure is 180/100 mmHg. Her blood results show increased blood urea nitrogen and serum creatinine. Following a CT scan investigation, the diagnosis of chronic pyelonephritis is made. Which of the following microscopic features is most likely to be present in her kidneys? A. Dilated renal tubules infiltrate with neutrophils B. Heavy infiltration of eosinophils and lymphocytes in renal tubules C. Renal tubular vacuolation D. Thyroidization of renal tubules 78. A 67-year-old diabetic man presents with difficulty passing urine for 3 days due to benign prostatic hyperplasia. An indwelling catheter is inserted. Five days later, he develops a low-grade fever with chills and rigors, and confirms to have a urinary tract infection (UTI). Which of the following conditions serves as the main predisposing factor for the development of UTI in this patient?. A. Benign prostatic hyperplasia B. Catheterisation C. Diabetes mellitus D. Old age 79. A30-year-old woman presents to the clinic with pain during micturition, increased frequency of urination for 3 days. Based on laboratory investigation, a diagnosis of Ureaplasma urealyticum urethritis is made. Which of the following specimens is best used to identify the causative organism? A. Blood B. Cervical swab C. Urine D. Vaginal swab 80. A 48-year-old woman is brought to the hospital with a severe headache and projectile vomiting. On examination, her Glasgow Coma Scale is 13/15 and the intracranial pressure is raised. The doctor plans to administer a diuretic by intravenous infusion. Which of the following diuretics is the most appropriate to be administered to the patient? A. Acetazolamide B. Furosemide C. Hydrochlorothiazide D. Mannitol

Here are all 20 questions (Q61-Q80) answered fully:

Q61. A 45-year-old man with progressive dysphagia (solids AND liquids), regurgitation of undigested food, heartburn. Manometry: esophageal aperistalsis, incomplete LES relaxation, increased LES tone. Diagnosis?

Achalasia ✓
Hiatal hernia
Esophageal atresia
Reflux esophagitis

Answer: Achalasia

Explanation:

The manometry findings are pathognomonic of achalasia:

Manometry Finding	Significance
Esophageal aperistalsis	Loss of coordinated peristaltic contractions - food not propelled down
Incomplete/absent LES relaxation	LES fails to open when food arrives - functional obstruction
Increased LES resting tone	LES hypertonic (normally ~15-25 mmHg; achalasia >45 mmHg)

Achalasia pathogenesis:

Loss of inhibitory neurons in myenteric (Auerbach's) plexus
(VIP and NO-producing neurons destroyed - likely autoimmune/idiopathic)
           ↓
Loss of inhibitory neurotransmission (VIP, nitric oxide)
           ↓
LES remains tonically contracted (fails to relax)
+ Esophageal body loses peristalsis (aperistalsis)
           ↓
Food accumulates in esophagus → dilated esophagus (megaesophagus)
           ↓
Regurgitation of UNDIGESTED food (not acidic - not yet reached stomach)
+ Dysphagia to BOTH solids AND liquids (key distinction from mechanical obstruction)

Key clinical distinction - dysphagia pattern:

Condition	Dysphagia Pattern
Achalasia	BOTH solids AND liquids (functional, not mechanical)
Esophageal carcinoma/stricture	Solids first, then progresses to liquids
Zenker's diverticulum	Regurgitation of undigested food, neck gurgling

Investigations:

Barium swallow: "Bird beak" sign (smooth tapering at GEJ)
Manometry: as described (gold standard for diagnosis)
Endoscopy: dilated esophagus, no carcinoma at GEJ (to exclude pseudoachalasia)

Treatment:

Pneumatic balloon dilation (endoscopic)
Heller myotomy (surgical - cut LES muscle)
Peroral endoscopic myotomy (POEM)
Botulinum toxin injection into LES (temporary, for poor surgical candidates)

Why not reflux esophagitis? GERD has LOW LES tone (not increased), normal peristalsis, and no aperistalsis.

Q62. A 20-year-old man with 4 months of intermittent mild diarrhea, fever, and abdominal pain. Diagnosed with Crohn's disease. Most likely morphological feature?

Cobblestone appearance of mucosa ✓
Diffuse lesions in colon and rectum
Inflammation limited to mucosa and submucosa
Superficial broad-based colonic ulcers

Answer: Cobblestone appearance of mucosa

Explanation:

Crohn's disease morphological features:

Gross/Endoscopic features:

Feature	Crohn's Disease	Ulcerative Colitis
Distribution	Skip lesions (discontinuous, segmental)	Continuous from rectum upward
Location	Any part of GI tract (mouth to anus), typically terminal ileum	Colon and rectum only
Mucosa pattern	"Cobblestone appearance" (islands of edematous mucosa between deep linear ulcers)	Pseudopolyps, granular mucosa
Ulcers	Deep, fissuring "rake/aphthous" ulcers → transmural	Superficial ulcers (mucosa only)
Bowel wall	Thickened ("garden hose"), strictures, fistulas	Thin (except toxic megacolon)
Fat wrapping	Creeping fat (mesenteric fat wraps around bowel)	Absent

Microscopic features of Crohn's:

Feature	Crohn's	UC
Depth	TRANSMURAL (full thickness)	Mucosa + submucosa only
Granulomas	Non-caseating granulomas (50%) - PATHOGNOMONIC	Absent
Fibrosis	Yes (leads to strictures)	Rare
Crypt architecture	Distorted	Distorted

"Cobblestone appearance" explained:

Deep linear ulcers intersect at right angles through the mucosa
Islands of normal/edematous mucosa are left between the ulcers
These islands look like cobblestones when viewed endoscopically
Pathognomonic of Crohn's disease

Why other options are wrong:

"Diffuse lesions in colon and rectum" = Ulcerative colitis pattern
"Inflammation limited to mucosa and submucosa" = UC (Crohn's is transmural)
"Superficial broad-based ulcers" = UC pattern

Q63. A 60-year-old chronic alcoholic with hepatic encephalopathy. Has ascites, flapping tremors (asterixis), jaundice, and PALMAR ERYTHEMA. What causes the palmar erythema?

Coagulopathy leading to bleeding
Elevated serum ammonia
Hyperestrogenemia causing local vasodilation ✓
Portosystemic shunts reversing blood flow

Answer: Hyperestrogenemia causing local vasodilation

Explanation:

Palmar erythema in chronic liver disease:

Mechanism:

Chronic alcoholic liver disease → HEPATIC FAILURE
           ↓
Liver cannot metabolize ESTROGENS
           ↓
HYPERESTROGENEMIA (elevated circulating estrogens)
           ↓
Estrogens → LOCAL VASODILATION of superficial arterioles and capillaries
in skin of thenar and hypothenar eminences of palms
           ↓
PALMAR ERYTHEMA (reddish blotchy discoloration of palms,
especially at thenar/hypothenar eminences and finger bases)

Stigmata of chronic liver disease caused by hyperestrogenemia:

Sign	Mechanism
Palmar erythema	Estrogen → skin arteriolar vasodilation
Spider naevi (spider telangiectasias)	Estrogen → central arteriole with radiating vessels
Gynecomastia	Estrogen → breast tissue stimulation in males
Testicular atrophy	Estrogen negative feedback on HPG axis
Loss of pubic/axillary hair	Hormonal imbalance

Why elevated ammonia is wrong for palmar erythema?

Ammonia causes hepatic encephalopathy (asterixis/flapping tremor, confusion, coma) - not palmar erythema

Why coagulopathy is wrong?

Coagulopathy → bruising, petechiae, bleeding - not the symmetric blotchy erythema pattern of palmar erythema

Why portosystemic shunts are wrong?

Portosystemic shunts cause ammonia to bypass the liver → encephalopathy - not palmar erythema

Q64. A 40-year-old woman with watery diarrhea, bloating, flatulence, fatigue for 1 year. Duodenal biopsy shows features of Celiac disease. Most likely cause of malabsorption?

Defect in transepithelial lipoprotein transport
Disaccharidase deficiency in brush border cells
Inadequate luminal hydration
Intestinal immune reaction to gluten ✓

Answer: Intestinal immune reaction to gluten

Explanation:

Celiac disease (Gluten-sensitive enteropathy) pathogenesis:

Gliadin (gluten fraction from wheat, barley, rye)
           ↓
Crosses intestinal epithelium → LAMINA PROPRIA
           ↓
Tissue transglutaminase (tTG) modifies gliadin → enhanced immunogenicity
           ↓
Deamidated gliadin presented by HLA-DQ2/DQ8 antigen-presenting cells
           ↓
CD4+ T cell activation → release of IFN-γ, TNF-α
           ↓
IMMUNE-MEDIATED DESTRUCTION of intestinal mucosa:
  → Villous atrophy (villi shortened/absent)
  → Crypt hyperplasia (crypts elongate - reactive)
  → Increased intraepithelial lymphocytes (IELs)
           ↓
LOSS OF ABSORPTIVE SURFACE AREA → MALABSORPTION

Histological changes in Celiac disease (Marsh classification):

Marsh Grade	Histology
1	↑Intraepithelial lymphocytes (>25/100 enterocytes)
2	+ Crypt hyperplasia
3a	+ Partial villous atrophy
3b	+ Subtotal villous atrophy
3c	Total villous atrophy (flat mucosa) = classic severe celiac

Why other options are wrong:

Defect in transepithelial lipoprotein transport: describes abetalipoproteinemia (Bassen-Kornzweig syndrome - failure to assemble chylomicrons)
Disaccharidase deficiency: describes lactase deficiency (lactose intolerance) or congenital disaccharidase deficiency - celiac does reduce brush border enzymes secondarily, but the PRIMARY mechanism is immune
Inadequate luminal hydration: describes cholera/secretory diarrhea mechanism

Celiac serology:

Anti-tTG IgA (most sensitive and specific for screening)
Anti-endomysial IgA (highly specific)
Anti-gliadin IgA/IgG (older, less specific)
HLA-DQ2 (90%) and HLA-DQ8 (5-10%) - negative HLA = excludes celiac

Treatment: Strict lifelong gluten-free diet (avoid wheat, barley, rye)

Q65. 16 college students with fever and bloody diarrhea after eating hamburgers. Two have low platelets and renal failure. Lab confirms food-associated infection. Which E. coli pathotype?

Enterotoxigenic E. coli (ETEC)
Enterohaemorrhagic E. coli (EHEC) ✓
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)

Answer: Enterohaemorrhagic E. coli (EHEC) - E. coli O157:H7

Explanation:

Key clues:

Hamburgers (undercooked beef) = classic EHEC source
Bloody diarrhea (hemorrhagic colitis)
Low platelets + renal failure = Hemolytic Uremic Syndrome (HUS)
Group outbreak = food poisoning

EHEC (E. coli O157:H7) virulence:

Ingestion of EHEC (E. coli O157:H7) from undercooked hamburger meat
           ↓
Colonizes large intestine (no invasion)
           ↓
Produces SHIGA-LIKE TOXIN / VEROTOXIN (Stx1, Stx2)
(encoded by prophage - bacteriophage)
           ↓
Stx inhibits protein synthesis (ribosomal 60S subunit inactivation)
           ↓
Intestinal effect: hemorrhagic colitis (bloody diarrhea, colonic ulceration)
           ↓
Stx enters bloodstream → targets vascular endothelium (especially renal microvasculature)
           ↓
HEMOLYTIC UREMIC SYNDROME (HUS):
  → Microangiopathic Hemolytic Anemia (low Hb, schistocytes)
  → Thrombocytopenia (low platelets - platelet consumption in microthrombi)
  → Acute Kidney Injury (renal microvascular thrombosis → oliguria/anuria)

HUS triad = MAHA + Thrombocytopenia + AKI (all present in this case)

E. coli pathotype comparison:

Pathotype	Key Feature	Disease
EHEC (O157:H7)	Shiga-like toxin (verotoxin)	Bloody diarrhea + HUS
ETEC	Heat-labile (LT) + heat-stable (ST) enterotoxins	Traveler's diarrhea (watery, no blood)
EPEC	Attaching and effacing (A/E) lesions	Infantile diarrhea (no blood)
EAEC	Aggregative adherence fimbriae	Persistent diarrhea (children/travelers)
EIEC	Shigella-like invasion	Dysentery (bloody, mucoid)

Why hamburgers? Cattle harbor EHEC in their intestines. Minced/ground beef can be contaminated with intestinal contents. Thorough cooking kills EHEC. Infectious dose is very low (~10-100 organisms) - hence outbreaks from small amounts.

Q66. A 30-year-old man with abdominal pain and bloody diarrhea. Stool shows leukocytes, erythrocytes, spiral-shaped bacteria. Campylobacter gastroenteritis diagnosed. Which virulence factor INDUCES INFLAMMATION?

Capsule
Cytolethal toxin
Fimbriae
Flagella ✓ (or Adhesins - see explanation)

Answer: Flagella (with explanation)

Explanation:

Note: This question asks specifically about inducing inflammation, and the options differ from the previous Campylobacter question (Q53/Q54 in earlier sets which listed "Adhesins"). Here the options are: capsule, cytolethal toxin, fimbriae, flagella.

Campylobacter jejuni virulence factors - roles:

Virulence Factor	Role
Flagella	Motility + invasion + immune evasion + directly induces inflammation
Cytolethal distending toxin (CDT)	DNA damage → cell cycle arrest → apoptosis → tissue damage (not primary inflammation inducer)
Capsule	Serum resistance, immune evasion
LOS/LPS	Endotoxin → inflammation, molecular mimicry (GBS)
CadF/FlpA (adhesins)	Initial attachment (not listed here)

Why flagella is the answer here (with the given options):

Flagella provide motility → enables colonization and invasion of intestinal mucosa
The flagellar T3SS-like apparatus secretes virulence proteins (Cia proteins) directly into host cells
Flagella components are recognized by TLR5 (Toll-like receptor 5) → triggers innate immune response → inflammatory cascade → neutrophil recruitment → mucosal inflammation → bloody diarrhea
Flagella also help the bacteria penetrate the mucus layer to reach epithelial cells

CDT (cytolethal distending toxin) vs Flagella for inflammation:

CDT causes cell death/apoptosis (contributes to tissue damage) but is more involved in cytopathic effect
Flagella = motility + direct inflammatory signal via TLR5 = more directly linked to initiating the inflammatory response

Among the listed options, Flagella is the best answer for inducing inflammation in Campylobacter gastroenteritis.

Q67. A family of four with abdominal cramps, diarrhea, nausea, vomiting ~5 hours after eating cheeseburger and pastries. Staphylococcal food poisoning confirmed. Which virulence factor is responsible?

Emetic toxin
Enterotoxin ✓
Toxic shock toxin
Verotoxin

Answer: Enterotoxin (Staphylococcal enterotoxin)

Explanation:

Staphylococcal food poisoning:

Staphylococcus aureus produces heat-stable enterotoxins (A-E, most commonly type A):

S. aureus grows in food (cheeseburger, pastries - high protein/carb)
           ↓
Produces ENTEROTOXIN (preformed) in food
           ↓
Food eaten → enterotoxin ingested
(TOXIN survives cooking that kills bacteria - heat STABLE at 100°C for 30 min)
           ↓
Enterotoxin acts on:
  1. GI tract mucosa → stimulates vagal afferents
  2. Brainstem vomiting center (toxin acts as superantigen)
           ↓
Rapid onset (1-6 hours) of:
  NAUSEA, VOMITING (prominent), diarrhea, abdominal cramps
  (short duration ~24h, self-limiting)

Key features confirming Staphylococcal food poisoning:

Short incubation (1-6 hours) - preformed toxin acts rapidly
Vomiting is the predominant symptom (not watery diarrhea as primary symptom)
Cream, custard, pastries, cheeseburgers = typical food vehicles (S. aureus from food handler)
No fever (toxin-mediated, not invasive)
Group clustering (all ate same food)

Why not "Emetic toxin"?

"Emetic toxin" specifically refers to Bacillus cereus emetic syndrome (reheated fried rice, very short incubation 1-6h, predominantly vomiting)
Staphylococcal toxin causing this presentation is correctly called enterotoxin (superantigen type)

Why not "Verotoxin"?

Verotoxin = Shiga-like toxin = EHEC (E. coli O157:H7) → bloody diarrhea + HUS, not the short-incubation vomiting syndrome

Virulence factor comparison for food poisoning:

Organism	Toxin	Incubation	Presentation
S. aureus	Enterotoxin (preformed, heat-stable)	1-6h	Vomiting + cramps
B. cereus (emetic)	Cereulide (emetic toxin, heat-stable)	1-6h	Vomiting
B. cereus (diarrheal)	Enterotoxin (heat-labile)	6-24h	Diarrhea
EHEC	Verotoxin/Shiga-like toxin	3-8 days	Bloody diarrhea + HUS
C. botulinum	Botulinum toxin (neurotoxin)	12-36h	Flaccid paralysis

Q68. A 38-year-old man with watery diarrhea and severe dehydration. Diagnosed with cholera. Which pathogenic mechanism?

Action of adenyl cyclase cyclic AMP on enterocytes ✓
Destruction of colonic villi by enterotoxin
Invasion of enterocytes by cytotoxin
Verotoxin action on colonic epithelial cells

Answer: Action of adenylyl cyclase - cyclic AMP on enterocytes

Explanation:

Cholera toxin (CT) mechanism - one of the most classic in all of pharmacology/microbiology:

Vibrio cholerae releases CHOLERA TOXIN (CT)
           ↓
CT = A subunit (toxic) + B pentamer (binds GM1 ganglioside on enterocytes)
           ↓
B subunit binds GM1 ganglioside → internalizes A subunit into cell
           ↓
A1 subunit: ADP-ribosylates Gs-alpha protein (stimulatory G protein)
           ↓
Gs-alpha permanently ACTIVATED → cannot hydrolyze GTP → stays active
           ↓
Gs-alpha continuously stimulates ADENYLYL CYCLASE
           ↓
↑↑↑cAMP (cyclic AMP) inside enterocytes
           ↓
cAMP activates Protein Kinase A (PKA)
           ↓
PKA phosphorylates CFTR (cystic fibrosis transmembrane regulator) chloride channel
           ↓
CFTR opens → massive Cl⁻ SECRETION into intestinal lumen
+ Inhibits NaCl absorption (Na⁺/H⁺ exchanger inhibited)
           ↓
Water follows Cl⁻ osmotically → "RICE-WATER" DIARRHEA (up to 20L/day)
           ↓
Severe dehydration → hypovolemic shock

CT vs other mechanisms:

Non-invasive (V. cholerae does NOT invade enterocytes)
No colonic villi destruction (cholera affects small intestine, and toxin does not destroy villi)
No verotoxin (that's EHEC/Shigella)

ORS (oral rehydration solution) works because:

Glucose-coupled Na+ transport (SGLT1) is NOT affected by cholera toxin
Glucose + Na+ co-transport remains intact → oral glucose drives Na+ and water absorption
This is the "physiological masterwork" of ORS therapy

Q69. A 28-year-old farmer with abdominal pain and bloody diarrhea, appears pale. Stool has Ancylostoma duodenale eggs. Mechanism of bloody diarrhea?

Rupture of capillaries in mucosa layer
Attachment of adult parasites to mucosa of small intestine ✓
Migration of larvae damages intestinal mucosa
Intestinal inflammation from eosinophilia

Answer: Attachment of adult parasites to mucosa of small intestine

Explanation:

Ancylostoma duodenale = hookworm (Old World hookworm)

Hookworm life cycle and pathogenesis:

Infective filariform larvae (L3) in soil → skin penetration (feet)
           ↓
Larvae → blood → lungs → bronchi → trachea → swallowed
           ↓
Arrive in small intestine → develop into ADULT WORMS
           ↓
ADULT HOOKWORMS:
  - Attach to small intestinal mucosa using TEETH/BITING PLATES
  - Bite through mucosa → expose capillaries → FEED ON BLOOD
  - Each worm consumes ~0.2mL blood/day (A. duodenale)
  - ANTICOAGULANT secreted → prevents blood clotting at bite site
  - Worm detaches and re-attaches → multiple bleeding sites
           ↓
BLOODY DIARRHEA + BLOOD LOSS → IRON DEFICIENCY ANEMIA (pallor)

Why adult worm attachment causes bloody diarrhea:

Adult hookworms have cutting plates/teeth that bite into the intestinal wall
They suck blood → blood in stool
They secrete anticoagulants (ancylostatin, hookworm anticoagulant peptide) → prolonged bleeding at attachment sites
Multiple worms → significant blood loss → iron deficiency anemia (pale patient)

Clinical picture explained:

Bloody diarrhea: from attachment/feeding
Pallor: iron deficiency anemia (chronic blood loss + dietary deficiency)
Abdominal pain: mucosal damage

Why not "larvae migration"?

Larvae migrating through lungs cause Löffler's syndrome (cough, wheeze, transient pulmonary infiltrates, eosinophilia) - NOT bloody diarrhea
Larvae in intestine develop into adults - the adult stage causes GI bleeding

Why not "eosinophilia-induced inflammation"?

Eosinophilia is a systemic response to tissue-invasive helminths but does not directly cause bloody diarrhea

Treatment: Albendazole or mebendazole (single dose) + iron supplementation

Q70. A 34-year-old man with acute high-grade fever and right hypochondrial pain. Had bloody diarrhea 2 months ago (untreated). Confirmed amoebic liver abscess. Which infective form is responsible?

Oocyst
Trophozoites ✓
Tachyzoites
Sporozoites

Answer: Trophozoites

Explanation:

Entamoeba histolytica life cycle and amoebic liver abscess:

Ingestion of CYSTS (infective stage) in contaminated food/water
           ↓
Cysts travel to large intestine → EXCYSTATION
           ↓
Each cyst → 4 TROPHOZOITES (active, motile form)
           ↓
Trophozoites colonize colon → INTESTINAL AMOEBIASIS
(bloody diarrhea 2 months ago in this patient)
           ↓
TROPHOZOITES invade colonic mucosa (using Gal/GalNAc lectins + amoebapores)
           ↓
Enter mesenteric venules → PORTAL CIRCULATION
           ↓
TROPHOZOITES travel to LIVER
           ↓
Multiply in liver parenchyma → destroy hepatocytes
           ↓
AMOEBIC LIVER ABSCESS
(usually right lobe - portal vein predominantly drains to right)
"Anchovy sauce/chocolate sauce" pus = lysed hepatocytes + dead trophozoites

Why trophozoites (not cysts) cause the abscess:

Cysts = dormant, infective for transmission, have no invasive capability
Trophozoites = ACTIVE, motile, invasive form - the pathogenic form
Trophozoites are the ones that:
- Invade colonic wall → bloody diarrhea
- Enter portal blood → travel to liver → form abscess

Why not the other options?

Oocysts: stage of Plasmodium/Cryptosporidium/Toxoplasma in definitive host - not Entamoeba
Tachyzoites: fast-replicating form of Toxoplasma gondii (causes toxoplasmosis) - not Entamoeba
Sporozoites: infective stage of Plasmodium (malaria) - not Entamoeba

Clinical features of amoebic liver abscess:

Right upper quadrant pain (liver is enlarged, tender)
High-grade fever
Tender hepatomegaly
Elevated right diaphragm on CXR
Ultrasound: round/oval hypoechoic lesion (usually right lobe)
Serology: anti-amoebic antibodies (IHA, ELISA) - >90% sensitivity

Treatment: Metronidazole (tissue amebicide) → followed by diloxanide furoate (luminal amebicide to eradicate intestinal cysts/trophozoites)

Q71. A 65-year-old man with GI stromal cell tumor (GIST) treated with imatinib mesylate. Mechanism of action?

Inhibition of proteasome
Inhibition of epidermal growth factor
Inhibition of topoisomerase I
Inhibition of tyrosine kinase ✓

Answer: Inhibition of tyrosine kinase

Explanation:

GIST (Gastrointestinal Stromal Tumor):

Arise from interstitial cells of Cajal (pacemaker cells of GI tract)
~85-90% have activating mutations in c-KIT (CD117) gene (receptor tyrosine kinase)
~5-10% have PDGFRA (platelet-derived growth factor receptor alpha) mutations
c-KIT mutation → constitutively active tyrosine kinase → uncontrolled cell proliferation

Imatinib mesylate (Gleevec/Glivec) mechanism:

c-KIT mutation → constitutively active tyrosine kinase receptor
           ↓
IMATINIB: small molecule that fits into the ATP-binding pocket of c-KIT
           ↓
Competitive inhibition of tyrosine kinase activity
(blocks ATP binding → cannot phosphorylate downstream proteins)
           ↓
RAS/MAPK and PI3K/Akt signaling pathways BLOCKED
           ↓
↓Proliferation → cell cycle arrest → apoptosis of GIST cells

Imatinib targets multiple tyrosine kinases:

c-KIT (CD117) - GIST, mastocytosis
BCR-ABL - Chronic Myeloid Leukemia (CML) - first indication for imatinib
PDGFRA/B - GIST, hypereosinophilic syndrome
ABL1 - Ph+ ALL

Targeted therapy comparison:

Drug	Target	Use
Imatinib	Tyrosine kinase (BCR-ABL, c-KIT)	CML, GIST
Bortezomib	Proteasome	Multiple myeloma
Erlotinib/Gefitinib	EGFR (epidermal GF receptor)	Lung adenocarcinoma
Irinotecan/Topotecan	Topoisomerase I	Colorectal, ovarian cancer
Trastuzumab	HER2	Breast cancer
Bevacizumab	VEGF (anti-angiogenic)	Multiple cancers

Q72. A 43-year-old man on metronidazole for intestinal amoebiasis drinks alcohol at a party. Which adverse effect occurs?

Diarrhea
Disulfiram reaction ✓
Metallic taste
Numbness

Answer: Disulfiram reaction

Explanation:

Metronidazole + Alcohol = Disulfiram-like reaction

Normal alcohol metabolism:

Alcohol → (alcohol dehydrogenase) → ACETALDEHYDE
               ↓
(aldehyde dehydrogenase = ALDH) → Acetic acid → CO2 + H2O

How metronidazole causes disulfiram reaction:

Metronidazole INHIBITS ALDH (aldehyde dehydrogenase)
           ↓
Acetaldehyde ACCUMULATES (cannot be metabolized further)
           ↓
ACETALDEHYDE TOXICITY = DISULFIRAM-LIKE REACTION:
  - Facial flushing
  - Throbbing headache
  - Nausea and vomiting
  - Tachycardia, palpitations
  - Hypotension
  - Sweating
  - Dyspnea
  - (Severe: arrhythmias, cardiovascular collapse)

Why "disulfiram reaction" specifically:

Disulfiram (Antabuse) is the classic drug that inhibits ALDH → used therapeutically for alcohol aversion therapy in alcohol use disorder
Metronidazole has the SAME mechanism → called "disulfiram-like reaction"

Other drugs that cause disulfiram-like reaction with alcohol:

Metronidazole (and other nitroimidazoles: tinidazole, secnidazole)
Cefoperazone, cefamandole, cefotetan (cephalosporins with MTT side chain)
Chlorpropamide (sulfonylurea)
Procarbazine

Why not "metallic taste"?

Metallic taste IS a known side effect of metronidazole itself (even without alcohol)
But the question asks what happens specifically when metronidazole + alcohol are combined → disulfiram reaction

Q73. A 3-year-old boy with infective gastroenteritis given loperamide. Pediatrician withdraws it. What condition is PREVENTED by withdrawing loperamide?

Intestinal perforation
Paralytic ileus
Systemic spread of infection
Toxic megacolon ✓

Answer: Toxic megacolon

Explanation:

Loperamide = opioid receptor agonist (μ-receptors in gut) → reduces intestinal motility + decreases secretion

Why loperamide is dangerous in infective gastroenteritis (especially in children):

Infective gastroenteritis (bacterial/parasitic - invasive organisms)
           ↓
LOPERAMIDE reduces intestinal motility (slows/stops peristalsis)
           ↓
Bacteria + toxins RETAINED in colon (not flushed out by diarrhea)
           ↓
INTESTINAL STASIS → 
  1. Bacteria overgrow → toxin accumulation
  2. Inflammatory mediators accumulate in colonic wall
  3. Colonic smooth muscle tone lost → COLONIC DILATATION
           ↓
TOXIC MEGACOLON:
  - Severely dilated colon (>6cm on X-ray)
  - Thin, friable, necrotic colonic wall
  - Risk of PERFORATION + PERITONITIS + SEPSIS + DEATH

Toxic megacolon features:

Massive colonic dilation
High fever, tachycardia, altered mental status
Abdominal distension
Leukocytosis

Specific dangerous scenarios for loperamide:

Invasive bacterial gastroenteritis: Shigella, Salmonella, EHEC (O157:H7), Campylobacter
Clostridium difficile colitis: absolutely contraindicated
Young children (this patient - age 3)
Amoebic colitis

Why loperamide is safe in some diarrhea:

Non-invasive, secretory diarrhea (e.g., mild traveler's diarrhea, IBS) - no bacterial invasion
Adults with mild uncomplicated diarrhea

The pediatrician is correct to withdraw loperamide - in infective gastroenteritis in children, the diarrhea is partially a defense mechanism (flushing out pathogens). Stopping motility traps toxins/bacteria → risk of toxic megacolon.

Q74. A 39-year-old man with heartburn, loss of appetite, skips meals, diagnosed with acute gastritis. Treated with omeprazole. Mechanism?

It blocks H2 receptor
It blocks M1 receptor
It inhibits H+/K+ ATPase ✓
It neutralizes gastric acid

Answer: It inhibits H+/K+ ATPase (proton pump)

Explanation:

Omeprazole = Proton Pump Inhibitor (PPI)

Mechanism in detail:

Omeprazole is a PRODRUG (inactive at neutral pH)
           ↓
Absorbed from small intestine → bloodstream
           ↓
Taken up by parietal cells of gastric mucosa
           ↓
In the ACIDIC SECRETORY CANALICULUS of parietal cells:
Omeprazole activated to SULFENAMIDE (active form, pH <4)
           ↓
Sulfenamide forms COVALENT DISULFIDE BOND with cysteine residues
on the EXTRACELLULAR (luminal) domain of H+/K+ ATPase (proton pump)
           ↓
IRREVERSIBLE inhibition of H+/K+ ATPase
           ↓
Proton pump cannot exchange H+ (into stomach) for K+ (into cell)
           ↓
PROFOUND SUPPRESSION of gastric acid secretion (up to 90%)
           ↓
Gastric pH rises → mucosal healing

Key pharmacology of PPIs:

Feature	Detail
Site of action	H+/K+ ATPase (proton pump) on luminal surface of parietal cells
Binding	Irreversible (covalent bond)
Activation	Requires acidic environment (prodrug)
Take before meal	Given 30-60 min before eating (stimulated proton pumps are more sensitive to PPI)
Duration	24-48h (new pump synthesis needed)
Drug class identification	Suffix: -prazole (omeprazole, lansoprazole, pantoprazole, esomeprazole)

Drug mechanism comparison (acid suppression):

Drug	Target	Effect
PPIs (omeprazole)	H+/K+ ATPase (proton pump)	Most potent (~90% reduction)
H2 blockers (famotidine)	H2 receptors on parietal cells	Moderate (~70% reduction)
Antacids (Mg(OH)2)	Neutralize HCl chemically	Rapid but short-acting
Pirenzepine	M1 muscarinic receptor	Reduce vagal-stimulated acid

Q75. A 4-year-old boy with facial puffiness, abdominal distension, pedal edema, massive proteinuria. Nephrotic syndrome. Responds well to steroids. Most likely cause?

Focal segmental glomerulosclerosis
Membranoproliferative GN
Membranous nephropathy
Minimal change disease ✓

Answer: Minimal change disease (MCD)

Explanation:

Key diagnostic clue: EXCELLENT RESPONSE TO STEROIDS

Feature	This Patient	MCD
Age	4-year-old	Peak 2-6 years (most common nephrotic in children)
Presentation	Facial puffiness, edema, proteinuria	Classic nephrotic syndrome
Steroid response	Responds well	~90% respond (hallmark)

MCD histological features:

Light microscopy: NORMAL (hence "minimal change")
Immunofluorescence: NEGATIVE (no immune deposits)
Electron microscopy: Diffuse podocyte foot process effacement (fusion) - the actual diagnostic finding

Why FSGS (focal segmental glomerulosclerosis) is wrong:

FSGS in children responds POORLY to steroids (~20-30% steroid-sensitive)
FSGS: segmental sclerosis visible on light microscopy (some glomeruli, some lobules)
FSGS is the most common nephrotic syndrome in adults/African Americans

Why Membranous Nephropathy is wrong:

Membranous nephropathy: spike and dome pattern, subepithelial deposits
Most common in adults (40-60y), responds poorly to steroids alone

Nephrotic syndrome causes by steroid response:

Diagnosis	Steroid Response
MCD	Excellent (~90%)
FSGS	Poor (~20-30%)
Membranous	Partial (requires additional immunosuppression)
MPGN	Poor

MCD pathogenesis: T-lymphocyte dysfunction → circulating permeability factor → podocyte injury → foot process fusion → proteinuria (as discussed in Q82 of the previous set)

Q76. A 75-year-old heavy smoker with hematuria, fatigue, weight loss. Renal mass with lung metastases. Biopsy: rounded-to-polygonal cells with abundant CLEAR CYTOPLASM. Neoplasm?

Angiomyolipoma
Clear cell carcinoma ✓
Oncocytoma
Papillary renal cell carcinoma

Answer: Clear cell carcinoma (Clear cell Renal Cell Carcinoma)

Explanation:

Pathognomonic finding: "Rounded to polygonal cells with ABUNDANT CLEAR CYTOPLASM"

Clear cell RCC:

Most common type of RCC (~70-75%)
Cells appear clear because cytoplasm is rich in glycogen and lipid → dissolve during tissue processing → clear appearance
Origin: proximal tubular epithelium

Classic clinical presentation:

Classic triad (late presentation): hematuria + flank pain + palpable mass ("too late triad")
Constitutional symptoms: fatigue, weight loss
Metastases commonly to: lungs, bone, liver, brain (lung metastases in this case)

Molecular pathology:

VHL (Von Hippel-Lindau) gene mutation/deletion (chromosome 3p25) in ~70-80% of sporadic clear cell RCC
VHL loss → ↑HIF (hypoxia-inducible factor) → ↑VEGF, PDGF → angiogenesis
Basis for targeted therapy: sunitinib (VEGFR inhibitor), sorafenib, pazopanib

Renal tumor comparison:

Tumor	Histology	Gross	Key Feature
Clear cell RCC	Clear cells (glycogen/lipid)	Golden yellow, vascular	VHL mutation, most common RCC
Papillary RCC	Papillary structures, foam cells	Gray/white, hemorrhagic	Trisomy 7/17, PRCC mutation
Chromophobe RCC	Large cells, distinct membranes, "halo"	Brown, homogeneous	BHD gene, best prognosis
Oncocytoma	Oncocytes (eosinophilic, mitochondria-rich)	"Mahogany brown", central scar	Benign
Angiomyolipoma	Fat + smooth muscle + blood vessels	Yellow (fat)	TSC1/2 mutation, benign
Wilms tumor	Triphasic (blast+stroma+epithelium)	-	Children 3-4y

Q77. A 54-year-old woman with recurrent UTIs, hypertension, elevated BUN and creatinine, diagnosed with chronic pyelonephritis. Most likely microscopic finding?

Dilated renal tubules infiltrated with neutrophils
Heavy infiltration of eosinophils and lymphocytes
Renal tubular vacuolation
Thyroidization of renal tubules ✓

Answer: Thyroidization of renal tubules

Explanation:

Chronic pyelonephritis histological hallmark = "Thyroidization"

"Thyroidization" of kidney:

Renal tubules become dilated and filled with homogeneous eosinophilic (pink) colloid-like material (actually inspissated Tamm-Horsfall protein + cellular debris)
The dilated tubules packed with pink casts resemble thyroid follicles on microscopy
Hence called "thyroidization" (looks like thyroid gland histology)

Chronic pyelonephritis microscopic features:

Feature	Description
Thyroidization	Dilated tubules filled with eosinophilic casts (colloid-like material)
Chronic inflammation	Lymphocytes, plasma cells, macrophages in interstitium
Tubular atrophy	Shrunken tubules (adjacent to dilated ones)
Interstitial fibrosis	Fibroblast proliferation, collagen deposition
Glomerular changes	Periglomerular fibrosis, hyalinized ("obsolete") glomeruli
Arterial changes	Intimal thickening (secondary hypertension)
Calyceal scarring	Cortical scarring overlying dilated calyces (on gross/IVP)

Why other options are wrong:

"Dilated tubules infiltrated with neutrophils" = acute pyelonephritis (neutrophil-filled tubules, WBC casts)
"Eosinophils and lymphocytes in renal tubules" = allergic interstitial nephritis (drug reaction - NSAIDs, penicillins)
"Renal tubular vacuolation" = hypokalemic nephropathy or osmotic nephropathy (contrast media, sucrose)

Gross pathology of chronic pyelonephritis:

Coarse, irregular scarring of kidney surface (especially upper and lower poles)
Scarring overlies dilated, blunted calyces (calyceal clubbing on imaging)
Asymmetric involvement

Q78. A 67-year-old diabetic man with BPH had urinary catheter inserted. Five days later develops UTI. What is the MAIN predisposing factor?

Benign prostatic hyperplasia
Catheterization ✓
Diabetes mellitus
Old age

Answer: Catheterization

Explanation:

Why catheterization is the MAIN predisposing factor (not BPH or DM):

Catheter-associated UTI (CAUTI) mechanism:

INDWELLING URINARY CATHETER
           ↓
BIOFILM FORMATION on catheter surface (within 24-48h):
  - Bacteria colonize catheter from periurethral area, hands, urine drainage bag
  - Biofilm protects bacteria from antibiotics and immune cells
           ↓
Bacteria ascend along catheter (EXTRALUMINAL route along catheter-urethral interface)
  OR intraluminal route (contaminated drainage system)
           ↓
Reach bladder → BACTERIURIA → UTI
(Risk increases ~5% per day of catheterization)
           ↓
After 5 DAYS of catheterization → UTI develops (as in this case)

Risk of UTI with indwelling catheter:

Day 1: ~1-3% per day
After 30 days: ~100% have bacteriuria
This patient: 5 days → high probability of CAUTI

Why catheterization > BPH or DM as the MAIN factor:

BPH caused the urinary retention requiring catheterization → BPH is the reason the catheter was inserted, but the catheter itself is the direct cause of the UTI
DM impairs immunity (neutrophil dysfunction, glucosuria promotes bacterial growth) but without the catheter, this patient would not have developed UTI in 5 days
The catheter is the direct, immediate, proximate cause of the UTI

Most common CAUTI organisms:

E. coli (most common)
Klebsiella pneumoniae
Candida spp. (in long-term catheters)
Pseudomonas aeruginosa
Enterococcus
Proteus mirabilis (urease → alkaline urine → struvite stones)

Prevention of CAUTI:

Use urinary catheter only when necessary
Remove catheter as soon as possible
Strict aseptic insertion technique
Maintain closed drainage system
Proper perineal care

Q79. A 30-year-old woman with dysuria and increased urinary frequency. Diagnosed with Ureaplasma urealyticum urethritis. Best specimen?

Blood
Cervical swab
Urine ✓
Vaginal swab

Answer: Urine

Explanation:

Ureaplasma urealyticum:

Smallest self-replicating organism (belongs to class Mollicutes, family Mycoplasmataceae)
No cell wall (intrinsically resistant to beta-lactams)
Produces urease (splits urea → ammonia) - this is its characteristic biochemical feature
Causes: non-gonococcal urethritis (NGU), cervicitis, epididymitis, PID, infertility, preterm birth

For urethritis (infection of urethra) - best specimen:

Ureaplasma urealyticum infects URETHRA and lower urogenital tract
           ↓
Presents with DYSURIA and URINARY FREQUENCY
           ↓
Organisms shed into URINE (especially first-void urine)
           ↓
URINE = best specimen for urethritis caused by Ureaplasma
(especially first-catch/first-void urine = highest concentration of urethral organisms)

Specimen selection for urogenital infections:

Infection Site	Best Specimen	Organism
Urethritis	First-void urine	Ureaplasma, Chlamydia, N. gonorrhoeae
Cervicitis	Cervical/endocervical swab	Chlamydia, N. gonorrhoeae
Vaginal infection	High vaginal swab	Candida, Trichomonas, BV
Upper tract (PID)	Endocervical + laparoscopy	Chlamydia, N. gonorrhoeae
Kidney (pyelonephritis)	Midstream urine	E. coli, Proteus

Why not cervical swab or vaginal swab?

This patient has URETHRITIS (urinary symptoms) not cervicitis or vaginitis
Cervical/vaginal swab would be appropriate if she had cervicitis or vaginal discharge

Ureaplasma detection:

Culture: special PPLO (pleuropneumonia-like organisms) medium with urea
NAAT/PCR: most sensitive and specific (preferred)
Serology: less useful

Treatment: Doxycycline or azithromycin (no cell wall → beta-lactams ineffective)

Q80. A 48-year-old woman with severe headache, projectile vomiting, GCS 13/15, and raised intracranial pressure. Doctor plans to give IV diuretic. Most appropriate diuretic?

Acetazolamide
Furosemide
Hydrochlorothiazide
Mannitol ✓

Answer: Mannitol

Explanation:

Raised ICP emergency = Mannitol is the drug of choice

Mannitol mechanism for reducing ICP:

MANNITOL (20% solution) given IV
           ↓
Mannitol is an OSMOTIC AGENT (does not cross BBB)
           ↓
Creates an OSMOTIC GRADIENT between blood and brain
(blood becomes hyperosmolar relative to brain tissue)
           ↓
Water moves from BRAIN PARENCHYMA → BLOODSTREAM
(down osmotic gradient, across BBB)
           ↓
REDUCED BRAIN WATER CONTENT → REDUCED BRAIN VOLUME
           ↓
REDUCED INTRACRANIAL PRESSURE (ICP)
           ↓
Onset: 15-30 minutes; Duration: 1.5-6 hours

Additionally:

Mannitol reduces blood viscosity → improves cerebral perfusion
Increases renal blood flow → osmotic diuresis (kidneys excrete the excess water + mannitol)

ICP management - mannitol indications:

Traumatic brain injury
Hemorrhagic/ischemic stroke with cerebral edema
Brain tumor with raised ICP
Acute raised ICP as in this patient (headache + projectile vomiting + reduced GCS)

Why not other diuretics for ICP?

Diuretic	Effect on Brain	Appropriate for ICP?
Mannitol	Osmotic gradient → draws water OUT of brain	YES - first choice
Furosemide	Systemic diuretic, also reduces CSF production	Sometimes used as adjunct to mannitol
Hydrochlorothiazide	Mild systemic diuretic, no specific ICP effect	NO
Acetazolamide	Reduces CSF PRODUCTION (carbonic anhydrase inhibitor)	Used for chronic ICP elevation (pseudotumor cerebri), not acute emergency

Other measures for acute raised ICP:

Head of bed elevation 30°
Avoid hypotension (maintain CPP = MAP - ICP)
Hyperventilation (CO2 → vasoconstriction → temporary ICP reduction, short-term only)
Sedation, corticosteroids (for tumor-related vasogenic edema)
Hypertonic saline (alternative to mannitol)
Surgical decompression if needed

Summary Table - Q61 to Q80

Q	Answer	Core Concept
61	Achalasia	Aperistalsis + incomplete LES relaxation + increased LES tone = achalasia
62	Cobblestone appearance	Crohn's: deep fissuring ulcers + edematous mucosa islands = cobblestone
63	Hyperestrogenemia causing vasodilation	Liver failure → cannot metabolize estrogens → hyperestrogenemia → palmar erythema
64	Intestinal immune reaction to gluten	Celiac: T-cell mediated immune reaction → villous atrophy → malabsorption
65	Enterohaemorrhagic E. coli	Hamburgers + bloody diarrhea + HUS (low platelets + renal failure) = EHEC O157:H7
66	Flagella	Flagella = motility + TLR5 activation + T3SS secretion → initiates inflammation
67	Enterotoxin	S. aureus preformed heat-stable enterotoxin → rapid (1-6h) vomiting + cramps
68	Action of adenylyl cyclase cAMP on enterocytes	Cholera toxin → ADP-ribosylates Gs → ↑cAMP → ↑Cl- secretion → rice-water diarrhea
69	Attachment of adult parasites to intestinal mucosa	Adult hookworms bite mucosa + secrete anticoagulants → blood loss → bloody diarrhea
70	Trophozoites	E. histolytica trophozoites (invasive form) cause intestinal invasion + liver abscess
71	Inhibition of tyrosine kinase	Imatinib blocks c-KIT ATP-binding site → no kinase activity → GIST cell death
72	Disulfiram reaction	Metronidazole + alcohol → ALDH inhibition → acetaldehyde accumulation → flushing/vomiting
73	Toxic megacolon	Loperamide in infective gastroenteritis → stasis → toxin accumulation → toxic megacolon
74	Inhibits H+/K+ ATPase	Omeprazole (PPI) irreversibly blocks proton pump → >90% acid suppression
75	Minimal change disease	Age 4 + nephrotic + excellent steroid response = MCD
76	Clear cell carcinoma	Clear cytoplasm (glycogen/lipid) + VHL mutation + lung mets = clear cell RCC
77	Thyroidization of renal tubules	Chronic pyelonephritis hallmark: dilated tubules with colloid-like casts = thyroidization
78	Catheterisation	Catheter = direct route for bacteria + biofilm formation = proximate cause of CAUTI
79	Urine	Urethritis → organisms shed in urine; first-void urine = best specimen
80	Mannitol	Osmotic agent → draws water from brain → reduces ICP; drug of choice for acute raised ICP

81. A 46-year-old alcoholic man presents to the hospital with abdominal distention. He is a known case of hypertension on enalapril. Further investigations reveal the diagnosis of cirrhosis of the liver. The physician prescribes him with oral spironolactone. Which of the following side effects of the prescribed drug could be expected in this patient? A. Hypercalcaemia B. Hyperkalaemia C. Hypoaldosteronism D. Hyponatraemia 82. A 58-year-old man presents with bilateral leg oedema since 1 month ago. He is previously well. He admits that he has been taking daily diclofenac for his chronic back pain for the past 6 years. He is suspected to have iatrogenic nephrotoxicity. Which of the following mechanisms of nephrotoxicity best explains the above drug effect? A. Crystal nephropathy B. Direct tubular cell injury C. Inflammatory changes in glomerulus D. Thrombotic microangiopathy 83. An 18-year-old woman in the first trimester of pregnancy presents with uterine bleeding and passing of grape-like vesicles per-vagina. She is diagnosed with a complete hydatidiform mole. Which of the following features is characteristic of the above diagnosis? A. Abnormal chorionic villi with diploid karyotype B. Abnormal chorionic villi with triploid karyotype C. Absence of chorionic villi with anaplastic trophoblasts D. Intermediate trophoblast cells with diploid karyotype 84. A 25-year-old woman presents with abdominal distension for the past 3 months. Ultrasonogram reveals an ovarian tumour which is later excised. Histologic sections from the tumour show a cyst lined by stratified squamous epithelium with underlying hair shafts, cartilage, adipose, tissue and intestinal gland. Which of the following diagnoses best fits the above description? A. Benign cystic teratoma B. Brenner tumour C. Dysgerminoma D. Serous cystadenoma 85. A 25-year-old woman presents with a painless, mobile lump in her left breast measuring 1x1 cm in size for the past 3 months. Lumpectomy is done and histologic sections reveal a well circumscribed tumour composed of proliferating fibroblastic stroma with low cellularity and elongated, compressed ducts. Which of the following diagnoses best fits the above description? A. Fibroadenoma B. Intraductal papilloma C. Invasive breast carcinoma D. Phyllodes tumour 86. A 68-year-old man is noted to have elevated Prostate Specific Antigen (PSA) level during annual medical check-up. On digital rectal examination, there is an irregular nodule in the peripheral zone of the prostate. Needle biopsy of the nodule confirms adenocarcinoma of the prostate. Which of the following histological features is expected to be seen in the above condition? A. Destruction of glands and necrotising granulomas B. Fibromuscular stroma and glands lined by bilayered epithelium C. Hyperplastic glands with papillae lined by bilayered epithelium D. Small, crowded glands lined by a single layer of epithelium 87. A 30-year-old man presents to the clinic with a painless, firm single ulcer on the external genitalia and enlarged inguinal lymph nodes filled with pus. He has a history of unprotected sex. Following investigations, he is diagnosed to have lymphogranuloma venereum (LGV). Which of the following tests is the most appropriate to identify the causative organism? A. Direct immunofluorescence B. Gram stain C. Silver impregnation stain D. Wayson's stain 88. A 37-year-old taxi driver presents with a painful non indurated genital ulcer covered by purulent exudate following unprotected sex with his partner. A Gram-stained smear of the ulcer aspirate shows Gram-negative short bacilli showing 'school of fish' appearance. Which of the following causative organisms is the most likely cause of the above infection? A. Calymmatobacterium granulomatis B. Chlamydia trachomatis C. Haemophilus ducreyi D. Treponema pallidum 89. A 45-year-old man presents to the clinic with fever, malaise and generalised lymphadenopathy for 2 weeks after an unprotected sex with a HIV infected partner. Following investigations, he is diagnosed to have early HIV infection. Which of the following properties of the virus best ensures its survival in the host cells? A. Ability to attach to the host cell. B. Ability to fuse viral DNA into the host genome. C. Ability to replicate in the lymph nodes. D. Ability to escape from phagocytosis. 90. A 30-year-old woman visits her gynecologist for family planning. The doctor prescribes oral combined contraceptive pills. Which of the following mechanisms best describes the effect of combining pills? A. It inhibits gonadotropin release B. It inhibits implantation C. It inhibits sperm transport D. It inhibits tubular motility 91. A 32-year-old woman, a known case of epilepsy is treated with sodium valproate. She is concerned about the drug's effect on her foetus if she conceives. Her doctor explains the possible teratogenic effects and that she needs to stop the medication if she becomes pregnant. Which of the following effects of the drug is the doctor most concerned about? A. Foetal hydantoin syndrome B. Neural tube defects C. Phocomelia D. Skeletal malformation 92. A 49-year-old woman presents with sweating and palpitation. She has a history of recurrent vaginal candidiasis and is on oral itraconazole. Since 2 days ago, she has been taking terenadine for allergic rhinitis. The doctor suspects her symptoms now are due to drug interaction. Which of the following effects best explains the symptoms in the patient? A. Hepatotoxicity B. Hypoglycemia C. Orthostatic hypotension D. Ventricular arrhythmia 93. A 49-year-old man with a history of Human Immunodeficiency Virus (HIV) infection 2 years ago is now diagnosed with acquired immunodeficiency syndrome (AIDS). He started on a tenofovir-based regimen. Which of the following mechanisms describes the action of the above drug? A. Inhibits integration of proviral DNA into host chromosome B. Inhibits nucleoside reverse transcriptase C. Inhibits nucleotide reverse transcriptase D. Inhibits protease enzyme 94. A 54-year-old man is brought to the Emergency Department with a new onset of seizure. His family members also note changes in his behaviour for the past 2 weeks. On examination, there is left hemiplegia. Imaging studies reveal an infiltrative mass measuring 4x4 cm in the left frontal lobe, suggestive of glioblastoma. The tumour is surgically resected. Which of the following histopathological features best describe the above pathology? A. Anaplastic cells with serpiginous areas of palisading necrosis B. Cells with fried egg appearance of cytoplasm C. Small round blue cells forming rosettes D. Spindle cells with Antoni A and Antoni B areas 95. A retrospective study is conducted on haemorrhagic stroke cases admitted to a tertiary hospital over the past 10 years. The result of the study reveals that for patients above 60 years of age, basal ganglia is the most common location of intracerebral haemorrhage. Which of the following conditions is the most likely predisposing factor for the development of intracerebral haemorrhage in the patients above? A. Amyloid angiopathy B. Arteriovenous malformation C. Systemic hypertension D. Thrombocytopenia 96. A 45-year-old man is brought to the neurologist with complaints of forgetfulness, short temper and abnormal movements for the past two months. On examination, he has repeated involuntary jerky movements and writhing movements in upper and lower limbs. Following investigations, he is diagnosed with Huntington disease. Which of the following mechanisms best explains the pathogenesis of the above condition? A. CAG trinucleotide repeat expansion in chromosome 4p16.3 B. Loss of dopaminergic neurons in substantia nigra C. Neurodegeneration mediated by Aß amyloid and tau protein D. Tau protein accumulation in frontal and temporal lobes 97. A 23-year-old primigravida delivers a baby at 28 weeks of gestation. The woman never had any antenatal check-up or taken folic acid supplements. On examination, the baby is noted to have an absent forebrain and top of skull. Which of the following processes is the most likely cause for the above anomaly? A. Agenesis of corpus callosum B. Arrest in migration of neurons to cerebral cortex C. Decreased generation of neurons in cerebral cortex D. Failure of closure of anterior end of neural tube 98. A 6-year-old boy is brought to the clinic with fever, headache, vomiting and a stiff neck. Investigation of the cerebrospinal fluid reveals numerous polymorphonuclear (PMN) leukocytes and predominantly Gram-negative diplococci that are both intracellular and extracellular. Which of the following features best characterizes the above condition? A. Deficiency of the early complement proteins predisposes to the infection. B. Infection has an insidious onset. C. It presents with purpuric rash on the extremities and trunk. D. Its pathogenicity is due to an autoimmune response. 99. A 32-year-old HIV positive man presents to the clinic with low-grade fever, headache, vomiting and neck stiffness for the past 10 days. Based on laboratory investigations a diagnosis of Cryptococcal meningitis is made. Which of the following laboratory tests is most likely used in the early diagnosis of this case? A. Antibody detection test B. Culture C. India ink stain D. PCR 100. An 8-year-old child is brought to the clinic with fever, drowsiness, headache, neck stiffness and irritability. Based on the laboratory investigations, a diagnosis of aseptic meningitis due to poliovirus is made. Which of the following specimens is used to isolate the causative organism? A. Blood B. Cerebrospinal fluid C. Stool D. Throat Swab

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