A 28-year-old man with Crohn's disease has ileocolonic involvement (Harvey-Bradshaw Index 12, elevated CRP, anaemia). He failed mesalazine and is on azathioprine 2 mg/kg for 6 months without remission. Which is the most appropriate step?
- A Increase azathioprine dose to 3 mg/kg
- B Switch to 6-mercaptopurine
- C Add anti-TNF therapy (infliximab or adalimumab) ✓
- D Start oral budesonide
Correct answer: C. Add anti-TNF therapy (infliximab or adalimumab)
Explanation
In moderate-to-severe Crohn's disease failing thiopurine therapy, anti-TNF biologics (infliximab — ACCENT I trial; adalimumab — CHARM trial) are the standard escalation per ECCO/NICE guidelines. Combination therapy with anti-TNF + azathioprine (SONIC trial) achieves superior mucosal healing and steroid-free remission compared to either alone. Simply increasing azathioprine beyond 2.5 mg/kg increases toxicity without benefit; switching to 6-MP offers no advantage.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.