A leprosy patient on dapsone monotherapy develops haemolytic anaemia and methaemoglobinaemia more severely than expected. The most likely explanation is:

• A Glucose-6-phosphate dehydrogenase (G6PD) deficiency causing oxidative red cell destruction ✓
• B Dapsone-induced folate deficiency causing macrocytic anaemia
• C Immune complex deposition on red cells (type II hypersensitivity)
• D Dapsone-induced aplastic anaemia through bone marrow suppression

Explanation

Dapsone undergoes CYP-mediated N-hydroxylation to form hydroxylamine metabolites, which oxidise haemoglobin Fe2+ to Fe3+ (methaemoglobin) and generate reactive oxygen species that damage red cell membranes. In G6PD-deficient patients, reduced glutathione cannot be regenerated, so oxidative damage is markedly amplified, causing severe haemolysis and methaemoglobinaemia at standard doses. Aplastic anaemia is a rare severe ADR, not dose-dependent.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.