Dengue - MBBS Yr 5 Exam One-Liners

1. Dengue is caused by Dengue virus (DENV), a single-stranded RNA virus of genus Flavivirus, family Flaviviridae.
2. Four antigenically distinct serotypes exist - DENV-1, DENV-2, DENV-3, DENV-4; infection with one gives lifelong immunity to that serotype but only transient immunity to others.
3. Secondary infection with a different serotype increases risk of severe dengue via antibody-dependent enhancement (ADE).

Osteoarthritis (OA) - Orthopaedics Exam One-Liners

1. OA is a degenerative joint disease characterized by progressive loss of articular cartilage with reactive subchondral bone changes - it is a "wear and tear" arthropathy, not primarily inflammatory.
2. Primary OA has no identifiable cause and is linked to age, sex, obesity/BMI, and genetic factors; secondary OA follows a clear insult - trauma, congenital dysplasia, avascular necrosis, septic arthritis, or metabolic/crystal disease.
3. Most commonly affected joints: knee, hip, hand (DIP, PIP, first CMC/thumb base), spine, and first MTP joint (big toe).

Osteoarthritis (OA) - Orthopaedics Exam One-Liners (Revised with Complete Classification)

1. OA is a degenerative joint disease characterized by progressive loss of articular cartilage with reactive subchondral bone changes - a "wear and tear" arthropathy, not primarily inflammatory.
2. Primary OA has no identifiable cause (linked to age, sex, obesity, genetics); secondary OA follows a clear insult - trauma, congenital dysplasia, avascular necrosis, septic arthritis, or metabolic/crystal disease.
3. Most commonly affected joints: knee, hip, hand (DIP, PIP, first CMC/thumb base), spine, and first MTP joint.

CLASSIFICATION SYSTEMS (Complete)

A. Kellgren-Lawrence (K-L) Radiographic Grading System (1957) - the most important and universally used scale for exam purposes

• Grade 2 or higher on K-L is generally the cutoff used in research/clinical practice to define "radiographic OA."
• K-L grade correlates poorly with symptom severity - a patient can have severe pain with Grade 1 changes or be asymptomatic with Grade 3-4 changes.
• Related/complementary scale: OARSI (Osteoarthritis Research Society International) grading scores osteophytes and joint space narrowing separately (each 0-3), giving a more granular semiquantitative assessment than K-L's single composite grade.

B. ACR (American College of Rheumatology) Clinical Classification Criteria - used to classify/diagnose OA in a given joint (distinct from K-L, which only grades radiographic severity)

• Clinical criteria alone (knee pain + at least 3 of the following 6):
  1. Age >50 years
  2. Morning stiffness <30 minutes
  3. Crepitus on active motion
  4. Bony tenderness
  5. Bony enlargement on exam
  6. No palpable warmth of the joint
• Clinical + radiographic criteria (knee pain + osteophytes on x-ray + at least 1 of the following 3):
  1. Age >50 years
  2. Morning stiffness <30 minutes
  3. Crepitus on active motion
• Clinical + laboratory criteria (knee pain + at least 5 of the following 9):
  1. Age >50 years
  2. Morning stiffness <30 minutes
  3. Crepitus on active motion
  4. Bony tenderness
  5. Bony enlargement
  6. No palpable warmth
  7. ESR <40 mm/hr
  8. Rheumatoid factor <1:40
  9. Synovial fluid signs consistent with OA (clear, viscous fluid)

1. ESR <20 mm/hr
2. Radiographic femoral or acetabular osteophytes
3. Radiographic joint space narrowing (superior, axial, and/or medial)

1. Hard tissue enlargement of 2 or more of 10 selected joints (bilateral 2nd and 3rd DIP, 2nd and 3rd PIP, 1st CMC joints)
2. Hard tissue enlargement of 2 or more DIP joints
3. Fewer than 3 swollen metacarpophalangeal (MCP) joints
4. Deformity of at least 1 of the 10 selected joints listed above

Bipolar Disorder - Psychiatry Exam One-Liners (with Complete Classification & Scoring)

1. Bipolar disorder is a chronic mood disorder characterized by recurrent episodes of mania/hypomania and depression, with a relapse rate exceeding 70% over 5 years.
2. Bipolar I disorder incidence is roughly equal in men and women; Bipolar II disorder is somewhat more common in women.
3. Mean age of onset is late teens to early 20s; genetic loading is high - first-degree relatives have markedly increased risk.

CLASSIFICATION (Complete - DSM-5-TR)

A. Manic Episode - Complete DSM-5 Criteria

1. Distractibility
2. Indiscretion (excessive involvement in risky/pleasurable activities - spending sprees, sexual indiscretions, foolish investments)
3. Grandiosity (inflated self-esteem)
4. Flight of ideas / racing thoughts
5. Activity increase (goal-directed activity or psychomotor agitation)
6. Sleep deficit (decreased need for sleep)
7. Talkativeness (pressured speech)

• The disturbance is severe enough to cause marked impairment in social/occupational functioning, necessitate hospitalization to prevent harm, or includes psychotic features.
• The episode is not attributable to substance use or another medical condition.
• A manic episode automatically qualifies for a diagnosis of Bipolar I disorder, regardless of whether a depressive episode has ever occurred.

B. Hypomanic Episode - Complete DSM-5 Criteria

1. Duration is shorter - at least 4 consecutive days (vs 1 week for mania).
2. The disturbance is NOT severe enough to cause marked impairment in functioning and does NOT require hospitalization.
3. There are NO psychotic features (presence of psychosis automatically makes it a manic, not hypomanic, episode).

• Change in functioning is observable to others but does not cause marked social/occupational impairment.

C. Major Depressive Episode (for context in bipolar diagnosis)

D. Bipolar Spectrum Disorders - Complete Definitions

• Episode duration cutoffs to remember: Mania = 1 week; Hypomania = 4 days; Major depressive episode = 2 weeks.
• Bipolar I depressive:manic/hypomanic episode ratio is approximately 3:1; Bipolar II depressive:hypomanic ratio is approximately 39:1 (depression dominates the course in Bipolar II).

SCORING TOOL - Young Mania Rating Scale (YMRS) - Complete

• 7 items scored 0-4 (mild increments): elevated mood, increased motor activity/energy, sexual interest, sleep (decreased need), language/thought disorder, appearance, insight.
• 4 items scored 0-8 (double-weighted due to being harder to quantify/more disruptive): irritability, speech (rate/amount), content (thought content - grandiosity/delusions), disruptive/aggressive behavior.

• Higher score = more severe mania.
• A score of ≥ 20 is generally used as the cutoff to indicate a manic episode of sufficient severity for clinical trials/treatment response criteria.
• A score around 30 indicates moderate mania.
• The scale is administered serially to track treatment response over time (e.g., a ≥50% reduction in YMRS score often defines "response" in clinical trials).

Irritable Bowel Syndrome (IBS) - Exam One-Liners

1. IBS is a functional gastrointestinal disorder characterized by recurrent abdominal pain associated with defecation or a change in bowel habit, in the absence of any identifiable organic cause.
2. It is a diagnosis based on symptom pattern (Rome IV criteria) plus limited/targeted investigation to exclude red-flag organic disease - it is not a diagnosis of exclusion requiring extensive workup in typical low-risk patients.

THE IMPORTANT CLASSIFICATION - Rome IV Diagnostic Criteria (Complete)

• Recurrent abdominal pain, on average at least 1 day per week in the last 3 months, associated with 2 or more of the following:
  1. Related to defecation (pain improves or worsens with passing stool)
  2. Associated with a change in stool frequency
  3. Associated with a change in stool form (appearance)
• Onset of symptoms at least 6 months before diagnosis, with criteria fulfilled for the last 3 months (i.e., 6-month total duration + 3-month active symptom criteria).

• Bloating/distension is a commonly associated symptom but is NOT part of the core Rome IV diagnostic criteria (removed as a primary criterion after Rome III).
• Rome IV (compared to Rome III) tightened the criteria - pain must be present, not just "discomfort," and frequency requirement increased to weekly - resulting in a somewhat lower prevalence estimate than Rome III.

Pleural Effusion - Exam One-Liners

1. Pleural effusion is abnormal accumulation of fluid in the pleural space between the visceral and parietal pleura, resulting from an imbalance between fluid formation and lymphatic reabsorption.
2. Any new pleural effusion detected on imaging is abnormal and warrants evaluation for underlying cause.

THE IMPORTANT CLASSIFICATION - Light's Criteria (Complete)

1. Pleural fluid protein / serum protein ratio > 0.5
2. Pleural fluid LDH / serum LDH ratio > 0.6
3. Pleural fluid LDH level > 2/3 of the upper limit of normal serum LDH

• Sensitivity for detecting exudates: ~98% (highest of all available tests).
• Specificity: ~70-83% (comparatively low) - Light's criteria over-call exudates, misclassifying 15-25% of true transudates (e.g., heart failure patients on diuretics) as exudates.
• If Light's criteria classify an effusion as exudate but the clinical picture strongly suggests a transudate (e.g., known heart failure), confirm with the serum-pleural fluid albumin gradient: a gradient < 1.2 g/dL supports a true exudate; do NOT use the albumin gradient alone as the primary test.
• Additional supportive tests: pleural fluid cholesterol >60 mg/dL, or pleural fluid/serum cholesterol ratio >0.3, favor exudate (higher specificity, lower sensitivity than Light's criteria).

Lung Cancer - Exam One-Liners (with Complete Classifications)

1. Lung cancer (bronchogenic carcinoma) is a malignant neoplasm arising from the respiratory epithelium; it is the leading cause of cancer death worldwide.
2. Smoking is the single most important risk factor (~85-90% of cases); other risk factors include asbestos, radon, occupational exposures, and family history.

CLASSIFICATION 1 - Histological Classification (Complete)

A. Non-Small Cell Lung Cancer (NSCLC) - ~85% of all cases

B. Small Cell Lung Cancer (SCLC) - ~15% of all cases

1. SCLC arises from neuroendocrine cells, is almost always centrally located, and is strongly associated with smoking.
2. Characterized by rapid tumor growth, early widespread metastasis, and high initial chemosensitivity - but poor overall prognosis due to early dissemination.
3. SCLC is staged differently from NSCLC - using a simplified Limited Stage (confined to one hemithorax, within a single tolerable radiation field, including ipsilateral hilar/mediastinal/supraclavicular nodes) versus Extensive Stage (any disease beyond limited stage, including distant metastasis or contralateral supraclavicular nodes) system, rather than full TNM staging, though TNM can still be applied for surgical candidates.
4. SCLC is most strongly associated with paraneoplastic syndromes (SIADH, Cushing syndrome from ectopic ACTH, and Lambert-Eaton myasthenic syndrome).

CLASSIFICATION 2 - TNM Staging (AJCC/IASLC 8th Edition) - Complete

T (Primary Tumor) categories

N (Regional Lymph Node) categories

M (Distant Metastasis) categories

Complete Stage Grouping

• Prefixes indicate the type of staging: cTNM = clinical (pretreatment), pTNM = pathologic (post-surgical resection), yTNM = post-treatment restaging.

Abnormal Uterine Bleeding (AUB) - Exam One-Liners

1. AUB describes any variation from normal menstrual bleeding parameters (frequency, regularity, duration, or volume) in non-pregnant women beyond menarche, present for at least 6 months.
2. Old confusing terms - "menorrhagia," "metrorrhagia," "dysfunctional uterine bleeding (DUB)" - have been formally discarded by FIGO/ACOG in favor of standardized terminology.
3. Normal menstrual parameters (FIGO System 1): frequency 24-38 days, duration ≤8 days, and cycle-to-cycle variation <7-9 days; heavy menstrual bleeding (HMB) = excessive blood loss (classically >80 mL) that interferes with quality of life.
4. Key terms: amenorrhea (absent menses), frequent bleeding (<24 days apart), infrequent bleeding (>38 days apart), intermenstrual bleeding (bleeding between periods), and breakthrough bleeding (unscheduled bleeding on hormonal therapy).

THE IMPORTANT CLASSIFICATION - FIGO PALM-COEIN System (Complete)

PALM - Structural causes

COEIN - Non-structural causes

• Structural (PALM) causes can be diagnosed with imaging (ultrasound, MRI) or histopathology; non-structural (COEIN) causes generally cannot be visualized and are diagnosed by history, labs, and exclusion.
• A patient can have multiple co-existing causes (e.g., a woman may have both a fibroid [L] and an underlying coagulopathy [C]) - the system allows multiple qualifying letters.
• The full nomenclature pairs the term AUB with a descriptor of the bleeding pattern (e.g., "AUB-HMB" or "AUB-IMB") plus the causative letter(s) (e.g., "AUB-L" for a fibroid-related AUB, "AUB-P" for polyp-related AUB).

Thyroid Carcinoma - Surgery Exam One-Liners (with Complete Classifications)

1. Thyroid carcinoma is malignancy arising from the thyroid gland - either from follicular cells (papillary, follicular, anaplastic) or parafollicular C-cells (medullary).
2. Most thyroid nodules are benign (~95%); thyroid cancer overall has an excellent prognosis given the predominance of well-differentiated subtypes.
3. Risk factors: prior neck irradiation, family history, MEN 2 syndrome (for medullary carcinoma), iodine deficiency (follicular carcinoma).

CLASSIFICATION 1 - Histological Classification (Complete)

A. Follicular cell-derived carcinomas

B. Parafollicular C-cell derived carcinoma

C. Other rare types

1. Thyroid lymphoma (~1-2%) - associated with Hashimoto thyroiditis, presents in patients >60 years with rapid growth.
2. Serum thyroglobulin is the key tumor marker for follow-up/recurrence detection in differentiated (papillary/follicular) carcinoma only - it is NOT produced by medullary or anaplastic carcinoma.

CLASSIFICATION 2 - AJCC/TNM Staging, 8th Edition (Complete) - Unique in using AGE as a staging variable

T (Primary Tumor) - same categories for all types

N (Regional Lymph Nodes)

• N0: No metastatic nodes
• N1a: Metastasis to level VI/VII (pretracheal, paratracheal, prelaryngeal/Delphian) nodes
• N1b: Metastasis to unilateral, bilateral, or contralateral cervical (levels I-V) or retropharyngeal/superior mediastinal nodes

M (Distant Metastasis)

• M0: No distant metastasis
• M1: Distant metastasis present

Complete Stage Grouping - Differentiated Thyroid Cancer (Papillary/Follicular) - KEY EXAM POINT: staging differs by age at diagnosis using cutoff of 55 years

Diverticulitis - Surgery Exam One-Liners (with Complete Classification)

1. Diverticulitis is inflammation/infection of a colonic diverticulum (an outpouching of mucosa and submucosa through the muscular wall, most commonly in the sigmoid colon), typically due to obstruction of the diverticular neck by fecalith leading to micro/macro-perforation.
2. Diverticulosis (presence of diverticula) is common with age; only a minority of patients with diverticulosis ever develop diverticulitis.
3. After a first attack of acute diverticulitis, about one-third of patients have a second attack; after the second episode, a further one-third have another attack.

THE IMPORTANT CLASSIFICATION - Hinchey Classification (Complete, including Modified versions)

Original Hinchey Classification (1978)

Modified Hinchey Classification by Wasvary (1999) - most widely adopted; adds Stage 0 and subdivides Stage I

Modified Hinchey Classification by Sher (subdivides Stage II by treatability)

• I: Pericolic abscess
• IIa: Distant abscess amenable to percutaneous drainage
• IIb: Complex abscess associated with fistula, or not amenable to percutaneous drainage
• III: Generalized purulent peritonitis
• IV: Fecal peritonitis

• Mortality rises sharply with stage: Hinchey III (purulent peritonitis) mortality ~6%, but Hinchey IV (fecal peritonitis) mortality rises dramatically to ~35%.
• Hinchey stage guides management: 0/Ia (uncomplicated) → outpatient/medical management; Ib/II (abscess) → antibiotics +/- percutaneous drainage; III/IV (peritonitis) → emergency surgery.

Blood Transfusion - Exam One-Liners (with Complete Classification)

1. Blood typing (ABO and Rh) and antibody screening of recipient serum, followed by crossmatching, must be performed before transfusion (except in life-threatening emergencies, where uncrossmatched O-negative blood may be given).
2. Whole blood is rarely transfused today; component therapy (separating whole blood into its constituents) is standard so patients receive only what they need.

1. Massive Transfusion Protocol uses PRBC:FFP:Platelets in roughly a 1:1:1 ratio to mimic whole blood in patients with massive hemorrhage.

THE IMPORTANT CLASSIFICATION - Transfusion Reactions (Complete)

A. ACUTE Reactions (occur within 24 hours)

B. DELAYED Reactions (occur days to weeks/years after transfusion)