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G6PD Deficiency Oxidative Haemolysis — RACP Adult Medicine MCQ

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ModerateClinical PharmacologyG6PD Deficiency Oxidative HaemolysisRACP Adult Medicine

A 50-year-old man with known glucose-6-phosphate dehydrogenase (G6PD) deficiency presents with dark urine and jaundice 2 days after commencing dapsone for dermatitis herpetiformis. His Hb has dropped from 140 to 85 g/L. Blood film shows bite cells and Heinz bodies. What has occurred?

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Correct answer: D — Oxidative haemolysis from dapsone in G6PD deficiency

Dapsone is a potent oxidant drug that causes dose-dependent haemolysis, which is dramatically exacerbated in G6PD-deficient individuals. Bite cells (from removal of Heinz body inclusions by splenic macrophages) and Heinz bodies (denatured haemoglobin) on blood film confirm oxidative haemolysis. Other drugs to avoid in G6PD deficiency include primaquine, nitrofurantoin, and sulfonamides. G6PD testing should be performed BEFORE prescribing known oxidant drugs.

Reference: AMH – 2025 – G6PD Deficiency Drug Interactions; eTG – 2025 – Haematology