Fulminant immune-related colitis after dual checkpoint inhibitor therapy: case report

<b>Aim:</b> Immune-related (IR) colitis is a potentially life-threatening complication of checkpoint inhibitors. Its presentation often includes diarrhea, abdominal pain and rectal bleeding and the median time to onset is 6-10 weeks post initiation of immunotherapy.<b>Case study:</b> We report an unusual case of fulminant IR-colitis beginning 3 days after the first dose of dual checkpoint blockade. IR-colitis was refractory to high-dose corticosteroids and was further complicated by sigmoid diverticulum perforation.<b>Conclusion:</b> Early-onset IR-colitis can occur, particularly in the context of combined anti-PD1 and anti-CTLA4 blockade, and clinicians should maintain a high-index of suspicion even when timing of symptom onset is atypical. Further research is needed to elucidate risk factors for early-onset IR-colitis.