Immune checkpoint inhibitors have been a major breakthrough in cancer treatment but can have many serious adverse effects. Pankti Reid, MD, MPH, assistant professor of medicine in rheumatology at the University of Chicago, discusses the pathogenesis, diagnosis, and treatment of toxicities from immune checkpoint inhibitors as outlined by the 2019 NCCN guidelines. Related Article: Management of Immunotherapy-Related Toxicities in Patients Treated With Immune Checkpoint Inhibitor Therapy