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Axial spondyloarthritis with active fistulising Crohn's disease — SCE Rheumatology MCQ

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ModerateGastroenterologyAxial spondyloarthritis with active fistulising Crohn's diseaseSCE Rheumatology

A 36-year-old man with radiographic axial spondyloarthritis has received etanercept for 3 years. He now has recurrent inflammatory spinal symptoms despite adherence: BASDAI is 6.4, spinal pain visual analogue score is 7.1 cm and MRI shows active sacroiliitis. He has also developed weight loss, abdominal pain and six bloody diarrhoeal stools daily. Ileocolonoscopy and histology confirm active ileocolonic Crohn’s disease. Pelvic MRI demonstrates a draining perianal fistula without an undrained abscess. A seton has been placed, and disease remains active despite an adequate course of corticosteroid, azathioprine and antibiotics. Infection screening has identified no contraindication to further advanced therapy. The rheumatology–gastroenterology multidisciplinary team wishes to use one treatment for both conditions. Which change in advanced therapy is most appropriate?

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Correct answer: E — Switch etanercept to infliximab

Infliximab is the best choice because it is a monoclonal TNF inhibitor with established efficacy and UK licensing for both severe active radiographic axial spondyloarthritis and fistulising Crohn’s disease. NICE specifically recommends infliximab for active fistulising Crohn’s disease after failure of conventional measures including antibiotics, drainage and immunosuppressive treatment. The absence of an undrained abscess is important before escalating immunosuppression. Bimekizumab and secukinumab inhibit IL-17. Although effective for axial spondyloarthritis, IL-17 inhibition is not recommended in active inflammatory bowel disease because new-onset or exacerbated disease can occur. Upadacitinib is licensed for both axial spondyloarthritis and Crohn’s disease and is therefore a credible alternative. However, where active inflammatory bowel disease coexists with axial spondyloarthritis, current rheumatology guidance gives preference to a monoclonal TNF inhibitor; the fistulising phenotype and specific NICE recommendation further favour infliximab here. Ustekinumab is effective for Crohn’s disease but has not demonstrated adequate efficacy for axial spondyloarthritis. Etanercept itself is a soluble TNF-receptor fusion protein rather than a monoclonal antibody and is ineffective for Crohn’s disease, so switching within the TNF-inhibitor class is appropriate.

Reference: The 2025 British Society for Rheumatology guideline for the treatment of axial spondyloarthritis with biologic and targeted synthetic DMARDs (2025) — https://pubmed.ncbi.nlm.nih.gov/40199504/ Infliximab and adalimumab for the treatment of Crohn's disease: Recommendations (19 May 2010) — https://www.nice.org.uk/guidance/ta187/chapter/1-Recommendations Flixabi 100 mg powder for concentrate for solution for infusion: Summary of Product Characteristics (October 2025) — https://www.medicines.org.uk/emc/product/7265/smpc