A case of immune-mediated adverse events enterocolitis and duodenitis with gastrointestinal bleeding successfully treated with ustekinumab.

Gastrointestinal immune-mediated adverse events (imAEs) complicated by bleeding may result in a severe clinical course. We report the case of a 64-year-old man with immune-mediated colitis who relapsed after initial treatment with prednisolone, improved following treatment with infliximab, but subsequently developed immune-mediated enterocolitis. Infliximab was reintroduced after hospitalization; however, his condition worsened and was complicated by bloody stools, then his condition progressed to hemorrhagic shock. A proton pump inhibitor was initiated, and upper gastrointestinal endoscopy revealed duodenal ulcers. The clinical course was considered consistent with immune-mediated enterocolitis complicated by duodenitis. Treatment with infliximab was discontinued and ustekinumab was initiated. Follow-up endoscopy showed no bloody retention in the duodenum; however, bloody stool persisted, suggesting additional bleeding sources in the small intestine or colon. Bloody stool improved 15 days after initiation of ustekinumab. ImAE sometimes cause severe gastrointestinal bleeding requiring blood transfusion. Although several immunosuppressive therapies have been reported to be effective in such cases, to our knowledge, ustekinumab has not been reported to be effective. This case highlights the potential role of ustekinumab as a therapeutic option for gastrointestinal imAEs complicated by bleeding.