ICI colitis is the most frequent irAE with anti-CTLA-4 or anti-PD-1+anti-CTLA-4 (combination ICI) therapy, and can present with the first ICI treatment or as late as greater than 4 mo after completing therapy (Berman et al., 2010; Tian et al., 2018). The gene discussed is CTLA4; the disease is colitis.