PDCD1 and colitis: Similarly, anti-PD-1-related colitis typically follows one of two patterns: active colitis with apoptosis (active inflammation, neutrophilic crypt micro-abscesses, increased crypt epithelial cell apoptosis, and presence of crypt atrophy/dropout) or lymphocytic colitis (increased intraepithelial lymphocytes in surface epithelium, surface epithelial injury, and expansion of the lamina propria).