Diarrhea represents a widespread manifestation, occurring in about 11% of patients receiving therapy with PD-1 axis inhibitors, while higher frequencies are recorded with CTLA-4 inhibitors (36%) and with the combination of the 2 drugs (44%).32 In such cases, diarrhea is a warning symptom for the possible presence of underlying colitis. The gene discussed is PDCD1; the disease is colitis.