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SpA-Associated IBD — RACP Adult Medicine MCQ

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ModerateGeneral Internal MedicineSpA-Associated IBDRACP Adult Medicine

A 40-year-old man with ankylosing spondylitis on adalimumab for 3 years develops new onset diarrhoea with blood. Colonoscopy shows patchy inflammation with granulomas. What is the most likely diagnosis?

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Correct answer: E — Crohn's disease (new diagnosis, potentially unmasked)

Approximately 5–10% of patients with ankylosing spondylitis develop inflammatory bowel disease (IBD), most commonly Crohn's disease. Subclinical gut inflammation is present in up to 60% of SpA patients. The patchy inflammation with granulomas is consistent with Crohn's disease. Importantly, adalimumab is already used for both SpA and Crohn's disease, so it should be continued (it treats both conditions). This is NOT drug-induced colitis. The IBD may have been subclinical before diagnosis.

Reference: eTG – 2025 – Rheumatology; eTG – 2025 – Gastrointestinal; ECCO – 2024