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Thiopurine Metabolite Monitoring — RACP Paediatrics MCQ

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HardGastroenterologyThiopurine Metabolite MonitoringRACP Paediatrics

A 13-year-old with Crohn's disease has been in remission on azathioprine for 2 years. Thiopurine metabolite monitoring shows elevated 6-MMP and low 6-TGN levels. He has abnormal LFTs. What does this metabolite pattern indicate?

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Correct answer: E — Thiopurine hypermethylation (shunting pathway)

Elevated 6-MMP with low 6-TGN indicates hypermethylation via TPMT, leading to hepatotoxicity (elevated LFTs) without therapeutic benefit. Management options include dose reduction with addition of allopurinol (to redirect metabolism to 6-TGN), or switching to methotrexate.

Reference: AUSPGHAN – 2024 – Position Statement on Therapeutic Drug Monitoring in IBD