Inflammatory colitis associated with Teriflunomide

•Teriflunomide is an oral disease modifying therapy for relapsing-remitting multiple sclerosis which can cause gastrointestinal side effects.•The gastrointestinal symptoms are usually mild and self-limiting.•Very rarely, inflammatory colitis has occurred which may be severe and require discontinuation of teriflunomide and initiation of colitis-specific anti-inflammatory treatment. Teriflunomide is an oral disease modifying therapy for relapsing-remitting multiple sclerosis (RRMS). Gastrointestinal (GI) side effects occurred in 15-17.9% of patients in the clinical trials and usually were mild and self-limiting. Few cases of inflammatory colitis related to teriflunomide and leflunomide, a prodrug which converts to teriflunomide and is used in the treatment of rheumatoid arthritis, have been reported but no clinical data is available except for a single case of lymphocytic colitis. We here report a 49-year-old man with RRMS who developed severe diarrhea and weight loss six months after starting teriflunomide and eventually was found to have multiple ulcers and inflammatory changes consistent with Crohn's disease. After stopping teriflunomide and chelation therapy, he was started on immunotherapy for Crohn's given the highly inflammatory degree of GI symptoms and histology findings.