Pharmacovigilance studies of immunotherapy-associated myocarditis show a higher incidence and increased severity in recipients of combination anti-CTLA-4 and anti-PD-1 immunotherapy, while approximately 25% of cases show evidence of myositis and 10% have features of myaesthenia gravis.19 Occurrence of all three is referred to as the ‘3M syndrome’, has a much lower incidence than myocarditis alone, and is more severe.20 Strikingly, all three described cases had characteristics of the ‘3M syndrome’. Here, PDCD1 is linked to 3M syndrome.