Dermatitis Herpetiformis — SCE Dermatology MCQ

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ModerateDermatopharmacologyDermatitis HerpetiformisSCE Dermatology

A 40-year-old woman on Dapsone for dermatitis herpetiformis has her routine blood tests checked. Her FBC shows a haemoglobin of 105 g/L (baseline 130 g/L) with reticulocytosis and raised bilirubin. Blood film shows Heinz bodies. What is the most likely cause?

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Correct answer: D — Dapsone-induced haemolytic anaemia

Dapsone commonly causes dose-dependent haemolysis (and methaemoglobinaemia) due to oxidative stress on red blood cells. Heinz bodies (denatured haemoglobin inclusions) on blood film, reticulocytosis, and unconjugated hyperbilirubinaemia are characteristic features of oxidative haemolysis. Haemoglobin typically drops by 1-2 g/dL. Pre-treatment G6PD screening is mandatory as G6PD-deficient patients are at high risk of severe haemolysis. FBC monitoring is required at initiation (weekly for first month, then regularly). Dose reduction may be needed if anaemia is significant. Methaemoglobinaemia causes cyanosis with normal PaO2.

Reference: BAD 2017 DH Guidelines; BNF Dapsone monitoring