New onset inflammatory bowel disease after initiation of anti-IL-17a treatment: a case series.

Immune mediated inflammatory diseases (IMIDs) are a heterogenous group of inflammatory disorders of joint, skin, and gut characterized by both shared and distinct pathological pathways. This complexity has therapeutic implications, as not all IMIDs exhibit responsiveness to available biologicals. Moreover, cases have been documented where patients undergoing biologic therapy experience paradoxical occurrences of either a new IMID or a flare-up of a previously asymptomatic one. Treatment with anti- IL-17a has been approved for ankylosing spondylitis, psoriasis, and psoriatic arthritis, but was not found effective for the treatment of inflammatory bowel disease (IBD). This case series describes four patients with new onset IBD under treatment with an IL-17a inhibitor for a rheumatological or dermatological indication.