A 35-year-old woman on dapsone for dermatitis herpetiformis develops hemolytic anemia. Her G6PD level is normal. Which mechanism best explains her hemolysis?
- A Immune-mediated complement activation against RBCs
- B Direct oxidation of hemoglobin to methemoglobin forming Heinz bodies ✓
- C Macrophage sequestration of antibody-coated RBCs
- D Intravascular complement lysis independent of G6PD
Correct answer: B. Direct oxidation of hemoglobin to methemoglobin forming Heinz bodies
Explanation
Dapsone undergoes N-hydroxylation to hydroxylamine metabolites, which directly oxidize hemoglobin to methemoglobin and form Heinz bodies in RBCs, leading to extravascular hemolysis. This occurs even without G6PD deficiency, though G6PD-deficient patients are far more susceptible. The dose-dependent hemolysis is an expected side effect monitored by CBC and reticulocyte count during therapy.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.