Summary

The cancer immunotherapy field has had many promising developments in recent years. Checkpoint inhibitors are good examples of that. This new class of medications comes with a new constellation of side effects that require early recognition and management. Here we present a patient with metastatic adenocarcinoma on pembrolizumab who was admitted to the hospital for colitis. This was found to be an immune-related adverse event from pembrolizumab. We discuss our work-up and approach to the diagnosis, then highlight important treatment pearls for internal medicine physicians who are increasingly taking care of such patients.