Pyruvate kinase (PK) deficiency causes hemolytic anemia. Unlike hereditary spherocytosis, the red cells in PK deficiency are NOT spherocytic; instead they may be echinocytic. The mechanism of hemolysis in PK deficiency is:
- A ATP depletion impairing Na/K-ATPase and membrane deformability, with premature destruction in spleen ✓
- B Defective spectrin leading to membrane instability
- C Oxidative damage to hemoglobin forming Heinz bodies
- D Complement-mediated lysis due to CD55/CD59 deficiency
Correct answer: A. ATP depletion impairing Na/K-ATPase and membrane deformability, with premature destruction in spleen
Explanation
Pyruvate kinase (PK) is the final step of glycolysis in RBCs; deficiency leads to ATP depletion since RBCs lack mitochondria and depend entirely on glycolysis for energy. ATP depletion impairs the Na/K-ATPase pump, causing ion imbalance, membrane rigidity, and loss of deformability. These rigid cells are trapped and destroyed primarily in the splenic sinusoids by extravascular hemolysis. Spectrin defects cause spherocytosis; Heinz body formation is due to G6PD deficiency; CD55/CD59 deficiency causes PNH.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.