Dapsone Monitoring — SCE Dermatology MCQ

Correct answer: A — Reduce Dapsone dose — dose-dependent haemolysis is expected and mild anaemia (Hb drop 1-2 g/dL) is acceptable if well tolerated

The correct answer is A, reduce dapsone dose, because dapsone causes a predictable, dose-dependent oxidative haemolysis in virtually all patients regardless of G6PD status, and this man's picture (mild fall in haemoglobin to 95 g/L, appropriate reticulocytosis, no bleeding, normal baseline G6PD) is the expected pharmacological effect rather than a dangerous idiosyncratic reaction. UK dermatology shared care guidance for dapsone specifically requires regular full blood count monitoring during treatment because of this known effect, and dose reduction (rather than cessation) is the recommended response to mild, well-tolerated anaemia so that the drug can still control the linear IgA disease. Stopping the drug outright is reserved for severe, symptomatic or rapidly progressive haemolysis, not a modest, asymptomatic drop with a compensatory reticulocyte response. Why the other options are wrong: E. Transfuse red cells: Transfusion is not indicated for a mild, asymptomatic Hb of 95 g/L with a reticulocyte response; transfusion is reserved for symptomatic or severe anaemia, not routine expected drug-related haemolysis. C. Stop Dapsone immediately: Discontinuing the drug abandons control of linear IgA disease unnecessarily; cessation is only needed for severe anaemia (for example Hb under 80 g/L), methaemoglobinaemia with symptoms, or haemodynamic compromise. B. Increase folic acid dose: Folic acid supports erythropoiesis in chronic haemolytic states but does not address the primary problem, which is dose-dependent oxidative haemolysis from dapsone itself; it will not prevent ongoing haemolysis. D. Check for GI bleeding: The elevated reticulocyte count without any bleeding history points to haemolysis, not blood loss, so investigating for GI bleeding is not the priority and would delay appropriate management. Key point: Dapsone causes universal dose-dependent haemolysis even with normal G6PD, so mild, asymptomatic anaemia with reticulocytosis should prompt dose reduction, not cessation, transfusion or bleeding work-up.

Reference: Royal Cornwall Hospitals NHS Trust, Dapsone for Adults in Dermatology Shared Care Guideline V1.1, 2026, https://doclibrary-rcht.cornwall.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Clinical/Pharmacy/DapsoneAdultsDermatologySharedCareGuideline.pdf