Life-threatening complications, such as bowel perforation, are present in severe cases.16,18–20 Diarrhea and colitis typically occur within 6–8 weeks from the beginning of treatment21,22 ; however, enterocolitis may manifest itself even several months after the end of therapy.19 The incidence is higher in case of anti-CTLA4 blockade, with diarrhea and colitis reported in 30–40%23,24 and 8–22% of cases,19,24 respectively. Here, CTLA4 is linked to colitis.