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Mycophenolate Side Effects — SCE Rheumatology MCQ

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ModerateRheumatology PharmacologyMycophenolate Side EffectsSCE Rheumatology

An adult with SLE has been clinically quiescent for 12 months while taking hydroxychloroquine and mycophenolate mofetil. Four weeks after the mycophenolate dose was increased from 1 g to 1.5 g twice daily, routine blood tests show a white cell count of 2.5 × 10^9/L and neutrophils of 1.1 × 10^9/L. Haemoglobin and platelet counts are normal, and the leucopenia is confirmed on repeat testing. There is no fever, viral prodrome, lymphadenopathy, splenomegaly or new lupus manifestation. CMV and EBV PCR and parvovirus B19 testing are negative. Anti-dsDNA titres are unchanged, complement levels are normal and urinalysis is inactive. What is the most likely cause of the leucopenia?

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Correct answer: A — Mycophenolate myelosuppression

The correct answer is A, mycophenolate myelosuppression. Mycophenolate is a recognised cause of leucopenia and neutropenia. The temporal relationship to dose escalation, isolated leucopenia with preserved haemoglobin and platelets, and absence of another identified cause make drug toxicity most likely. Stable anti-dsDNA and normal complement do not alone exclude an SLE flare, but the absence of clinical, renal or other laboratory evidence of activity makes flare-related leucopenia less likely. Viral infection has been specifically assessed and is unsupported clinically. Felty syndrome occurs in association with rheumatoid arthritis, usually with splenomegaly. Aplastic anaemia ordinarily produces pancytopenia rather than isolated leucopenia. This neutrophil count warrants prompt specialist review and consideration of interrupting or reducing mycophenolate while other causes are excluded.

Reference: Electronic Medicines Compendium. Mycophenolate Mofetil 500 mg film-coated tablets: Summary of Product Characteristics, sections 4.4 and 4.8. Updated 8 June 2026. https://www.medicines.org.uk/emc/product/101918/smpc