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Azathioprine myelotoxicity risk — SCE Rheumatology MCQ

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HardRheumatological PharmacologyAzathioprine myelotoxicity riskSCE Rheumatology

A patient taking azathioprine has severe myelosuppression despite normal TPMT activity. Genotyping identifies reduced-function NUDT15 variants. What is the relevance?

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Correct answer: CThiopurine toxicity can occur independently of TPMT status

NUDT15 variants can markedly increase thiopurine-related leucopenia even when TPMT is normal. Pharmacogenetic assessment reduces but does not eliminate risk; dose selection, early blood-count monitoring and prompt action on cytopenia remain essential.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/musculoskeletal-conditions