A Case of Immune Checkpoint Inhibitor–Induced Duodenitis

Immune checkpoint inhibitors improve patient survival in multiple cancers, but immune-related adverse events, including new immunologic conditions arising during therapy, pose a significant challenge. Gastrointestinal immune-related adverse events, although common, exhibit diverse presentations. We present a case of duodenitis resembling celiac disease because of the anti-programmed cell death protein-1 antibody, pembrolizumab. Despite diagnostic uncertainty and therapeutic interventions, including gluten-free diet, symptoms stabilized even with resuming gluten. In addition, endoscopic abnormalities after pembrolizumab therapy have neither progressed nor completely resolved. This case underscores the need for investigation into the pathogenesis of immune checkpoint inhibitor-induced duodenitis, with implications for care of patients on immunotherapies.