Two PD-1 inhibitors (nivolumab and pembrolizumab), three PD-L1 inhibitors (atezolizumab, durvalumab, and avelumab), and one CTLA-4 inhibitor (ipilimumab) have been approved by the US Food and Drug Administration (FDA) for a myriad of cancers.3 With the ever-increasing use of ICIs across cancers, both in the frontline and relapsed setting, the incidence of ICI-related pneumonitis is likely higher than reported in the existing literature. The gene discussed is CTLA4; the disease is pneumonitis.