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Drug-Induced Folate Deficiency — RACP Adult Medicine MCQ

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EasyHaematologyDrug-Induced Folate DeficiencyRACP Adult Medicine

A 40-year-old woman on methotrexate for rheumatoid arthritis presents with macrocytic anaemia (Hb 98 g/L, MCV 105 fL). B12 is normal. Red cell folate is 180 nmol/L (normal >340). Reticulocyte count is low. What is the most likely diagnosis?

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Correct answer: E — Folate deficiency

Macrocytic anaemia with low red cell folate in a patient on methotrexate (a folate antagonist) is folate deficiency. Methotrexate inhibits dihydrofolate reductase, depleting folate stores. Folic acid supplementation (5 mg weekly, not on the same day as methotrexate) is standard prophylaxis for patients on methotrexate.

Reference: eTG Haematology – 2024 – Folate Deficiency; BSH 2024