In a study of fatal myocarditis in patients with melanoma who were treated with a combination of the immune checkpoint inhibitors ipilimumab (targeting CTLA-4) and nivolumab (targeting PD-1), two patients developed severe myocarditis and myositis, accompanied by extensive T cell and macrophage infiltration in the myocardium and skeletal muscle. This evidence concerns the gene CTLA4 and myocarditis.