A 30-year-old man with known Crohn's disease (ileal and colonic) is on azathioprine 2.5 mg/kg/day and has been in remission for 18 months. He now presents with a perianal fistula and recurrence of abdominal symptoms (CDAI 280). Anti-TNF levels are not applicable (not on anti-TNF). The best next management step is:
- A Increase azathioprine dose to 3.5 mg/kg
- B Add an anti-TNF agent (infliximab or adalimumab) — consider combination therapy with azathioprine (SONIC trial evidence) ✓
- C Oral metronidazole alone for the fistula
- D Initiate vedolizumab as first biologic choice for perianal fistulising disease
Correct answer: B. Add an anti-TNF agent (infliximab or adalimumab) — consider combination therapy with azathioprine (SONIC trial evidence)
Explanation
For moderate-to-severe Crohn's disease with perianal fistulising disease failing immunomodulator therapy, anti-TNF agents — particularly infliximab — are first-line biologics. The SONIC trial demonstrated superior remission with infliximab plus azathioprine combination (combination therapy) versus either alone. Infliximab is also the only biologic with RCT evidence (ACCENT II trial) for maintenance of fistula closure. Vedolizumab has limited efficacy data for fistulising disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.