A patient with G6PD deficiency develops acute hemolytic anemia after eating fava beans. Peripheral smear shows 'bite cells' and Heinz bodies. The fundamental mechanism of RBC destruction is:

• A Complement-mediated intravascular lysis due to absence of CD55/CD59
• B Antibody-mediated opsonization and phagocytosis in the spleen
• C Mechanical fragmentation of RBCs in capillaries
• D Oxidative denaturation of hemoglobin forming Heinz bodies, with splenic removal of affected cells ✓

Explanation

G6PD deficiency impairs regeneration of NADPH (via pentose phosphate pathway), leaving hemoglobin vulnerable to oxidative denaturation. Denatured hemoglobin precipitates as Heinz bodies, which damage the cell membrane; splenic macrophages 'bite' out these inclusions, producing bite cells that are then removed by the spleen. CD55/CD59 deficiency is the mechanism in PNH. Antibody-mediated is warm AIHA.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.