A 25-year-old West African man develops acute hemolysis after taking primaquine. Peripheral smear shows bite cells and Heinz bodies on crystal violet stain. The enzyme deficiency responsible causes hemolysis because:

• A Deficient pyruvate kinase reduces ATP, causing membrane rigidity
• B Inadequate NADPH production impairs glutathione reduction and oxidant defense ✓
• C Absent spectrin leads to spherocyte formation and splenic trapping
• D Deficient Band 3 protein impairs CO2 transport and membrane stability

Explanation

G6PD deficiency impairs the HMP shunt, reducing NADPH production. NADPH is required by glutathione reductase to regenerate reduced glutathione (GSH), which neutralizes oxidants. Without GSH, hemoglobin is oxidized, forming Heinz bodies that cause splenic removal of membrane ('bite cells'). Pyruvate kinase deficiency causes non-spherocytic hemolysis; spectrin deficiency causes hereditary spherocytosis; Band 3 deficiency causes hereditary spherocytosis/elliptocytosis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.