Answer fast according to university exam

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Here are concise exam-style answers (3-5 marks each):

1. Why pneumococcal vaccination in adolescent with sickle cell anemia (3)

Recurrent vaso-occlusion and infarction of the spleen from sickling leads to functional/autosplenectomy by adolescence.
Spleen normally filters encapsulated bacteria (S. pneumoniae, H. influenzae) via opsonization.
Loss of splenic function → high risk of overwhelming pneumococcal sepsis (a major cause of death in SCA).
Hence pneumococcal (and Hib, meningococcal) vaccination is advised to prevent fatal infection.

2. Lab investigations in hemolytic anemia (3)

CBC: low Hb, reticulocytosis (raised retic count - marrow response)
Peripheral smear: spherocytes/schistocytes/sickle cells depending on cause
Increased indirect (unconjugated) bilirubin, increased LDH, decreased serum haptoglobin
Increased urobilinogen in urine/stool
Direct Coombs test (for autoimmune hemolysis), osmotic fragility test, Hb electrophoresis as indicated

3. Pathogenesis of Sickle cell disease (3)

Point mutation in beta-globin gene (GAG→GTG) → glutamic acid replaced by valine at position 6 → HbS
On deoxygenation, HbS polymerizes into rigid rod-like fibers → RBC becomes sickle-shaped
Sickled cells are rigid, less deformable → increased blood viscosity, vaso-occlusion of microvasculature → ischemia, infarction, pain crises
Repeated sickling damages RBC membrane → extravascular/intravascular hemolysis → chronic hemolytic anemia

4. Why iron deficiency anemia produces microcytic hypochromic cells (3)

Iron is essential component of heme synthesis
Deficient iron → reduced heme synthesis → reduced hemoglobinization of erythroid precursors
Cells undergo extra divisions to try to maintain Hb concentration → smaller cell size (microcytic)
Reduced Hb content per cell → pale/hypochromic appearance with increased central pallor on smear

5. Why aplastic anemia causes pancytopenia (5)

Aplastic anemia = bone marrow failure due to destruction/suppression of hematopoietic stem cells (autoimmune T-cell mediated, drugs, toxins, viruses, or idiopathic)
Stem cells give rise to all three cell lines: erythroid, myeloid, megakaryocytic
Damage to the common pluripotent stem cell pool → failure of production of RBCs, WBCs, and platelets simultaneously
Marrow shows hypocellularity/fatty replacement on biopsy
Result: anemia (fatigue), leukopenia (infections), thrombocytopenia (bleeding) - the triad of pancytopenia

6. Why unconjugated bilirubin is increased in hemolytic anemia (5)

Increased RBC destruction (intra/extravascular) → excess Hb released → broken down to heme → heme catabolized by macrophages (spleen/liver) to unconjugated (indirect) bilirubin
Rate of production exceeds the liver's conjugating capacity (glucuronidation by UDP-glucuronyl transferase)
Liver conjugating machinery is normal but overwhelmed by the excessive load
Hence unconjugated bilirubin accumulates in blood → indirect hyperbilirubinemia, mild jaundice, increased urobilinogen (conjugated bilirubin normal/near normal since liver function intact)

7. Why severe beta-thalassemia major causes facial bone deformities and splenomegaly (3)

Defective/absent beta-globin chain synthesis → severe chronic anemia → compensatory massive erythroid hyperplasia
Marrow expansion in skull and facial bones ("chipmunk facies," frontal bossing, maxillary hypertrophy) due to extramedullary/intramedullary erythropoiesis
Ineffective erythropoiesis + extramedullary hematopoiesis (liver, spleen) and increased RBC destruction → hepatosplenomegaly
Chronic hemolysis also contributes to splenic enlargement (splenic work hypertrophy)

8. Why sickle cell disease patients develop severe joint pain (3)

Sickled RBCs are rigid and adhere to vascular endothelium → occlude small blood vessels supplying bone marrow/joints
Vaso-occlusion → tissue ischemia and infarction of bone marrow (especially in long bones, vertebrae)
Ischemia triggers release of inflammatory mediators and pain fibers activation → acute vaso-occlusive (painful) crisis
Can also cause avascular necrosis of femoral/humeral head with chronic joint pain

9. Why hypersegmented neutrophils are seen in megaloblastic anemia (3)

Deficiency of vitamin B12/folate impairs DNA synthesis (thymidylate synthesis) in all rapidly dividing cells, including myeloid precursors
Nuclear maturation is delayed relative to cytoplasmic maturation (asynchrony)
Defective DNA synthesis affects nuclear division/segmentation control in maturing neutrophils
Results in neutrophils with 6 or more nuclear lobes (hypersegmentation) - a characteristic peripheral smear finding

10. Why vitamin B12 deficiency leads to megaloblastic anemia (3)

B12 is a cofactor for methionine synthase, converting homocysteine to methionine, which regenerates tetrahydrofolate from methyl-THF
B12 deficiency traps folate as methyl-THF (methylfolate trap) → unavailable for DNA synthesis
Impaired thymidylate/DNA synthesis → nuclear maturation lags behind cytoplasmic maturation
Results in large, immature-nucleus erythroid precursors (megaloblasts) → ineffective erythropoiesis and macrocytic anemia

11. Why sickle cell anemia leads to autosplenectomy (3)

Repeated splenic sequestration of sickled RBCs causes recurrent microinfarcts in the spleen
Chronic ischemic damage leads to progressive fibrosis and shrinkage of splenic tissue
Over time (usually by childhood/adolescence) the spleen becomes small, fibrotic, and non-functional
This "autosplenectomy" leaves the patient functionally asplenic, predisposing to infections by encapsulated organisms

12. Why prolonged immobilization is a risk factor for DVT (3)

Immobilization causes venous stasis due to loss of the calf muscle pump that normally propels venous blood back to the heart
Stasis promotes local accumulation of activated clotting factors and platelets (Virchow's triad: stasis, endothelial injury, hypercoagulability)
Reduced blood flow favors contact activation of coagulation cascade and reduces clearance of clotting factors
Together these favor thrombus formation in deep veins, typically of the lower limb

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Answer according to university

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1. 60-yr-old woman with back pain, anemia, multiple punched-out lytic skull lesions (5)

This triad is classic for Multiple Myeloma (plasma cell dyscrasia):

Malignant plasma cells proliferate clonally in bone marrow and secrete monoclonal Ig (paraprotein) and cytokines (RANKL, IL-6, MIP-1α) that activate osteoclasts and suppress osteoblasts → focal bone resorption → sharply demarcated, punched-out lytic lesions without surrounding sclerosis (classically seen in skull, spine, pelvis) - Rheumatology, 2-Vol Set.
Bone destruction → back pain (vertebral involvement/compression fractures) and hypercalcemia.
Anemia results from marrow infiltration by plasma cells (crowding out normal hematopoiesis) plus cytokine-mediated suppression of erythropoiesis and renal impairment (reduced erythropoietin).
Diagnosis confirmed by monoclonal plasma cells on marrow biopsy, M-spike on serum/urine protein electrophoresis (Bence Jones proteinuria), and skeletal survey/MRI showing lytic lesions - Rheumatology, 2-Vol Set, p.3234.

2. Mechanism by which Multiple Myeloma causes Bone, Neurological and Kidney dysfunction (3)

Bone: Myeloma cells increase osteoclast activity (via RANKL/OPG imbalance, IL-6, MIP-1) and inhibit osteoblasts → osteolytic lesions, pathological fractures, hypercalcemia.
Neurological: Cord/nerve root compression from vertebral collapse or plasmacytoma; hypercalcemia causing confusion; hyperviscosity from paraprotein; amyloid or light-chain deposition causing peripheral neuropathy - Harrison's Principles of Internal Medicine, 22E.
Kidney: Excess free light chains (Bence Jones protein) are filtered and precipitate with Tamm-Horsfall protein in distal tubules forming casts → tubular obstruction and "myeloma cast nephropathy"; light chains are also directly toxic to proximal tubular cells; hypercalcemia causes nephrocalcinosis and reduces GFR; amyloid deposition (AL amyloidosis) can cause nephrotic-range proteinuria - together producing myeloma-associated renal failure.

3. Why patients with chronic liver disease develop a bleeding tendency (3)

Liver synthesizes most clotting factors (I, II, V, VII, IX, X, XI) as well as anticoagulant proteins (protein C, S, antithrombin) - in CLD synthesis of pro-coagulant factors is reduced, prolonging PT/aPTT.
Vitamin K-dependent factors (II, VII, IX, X) are further reduced due to impaired bile secretion/malabsorption of fat-soluble vitamin K.
Thrombocytopenia occurs due to hypersplenism from portal hypertension (splenic sequestration of platelets) and reduced hepatic thrombopoietin production.
Note: because anticoagulant factor synthesis is reduced in parallel, the hemostatic balance is often "re-set" rather than simply hypocoagulable - conventional PT/aPTT can overestimate true bleeding risk (Barash's Clinical Anesthesia, 9e), but clinically, bleeding (variceal, mucosal, procedural) remains a major risk especially with superimposed portal hypertension and endothelial dysfunction.

4. Why patients with nephrotic syndrome develop generalized edema (3)

Heavy proteinuria (>3.5 g/day) from damaged glomerular basement membrane → loss of albumin → hypoalbuminemia.
Reduced plasma oncotic pressure → fluid shifts from intravascular to interstitial space → edema ("underfill" mechanism).
Reduced effective circulating volume activates RAAS and sympathetic system → renal sodium and water retention, worsening edema ("overfill" mechanism, now considered the dominant mechanism in many patients - primary renal Na+ retention via activated distal nephron ENaC channels, independent of oncotic pressure).
Edema is typically dependent, pitting, and prominent periorbitally in the morning, generalizing to anasarca with ascites/pleural effusion in severe cases (Comprehensive Clinical Nephrology, 7th Ed, Tintinalli's Emergency Medicine).

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