PDCD1 and myositis disease: Immune checkpoint blockade (ICB) with anti-PD-1 monoclonal antibodies is approved for treatment of melanoma in adjuvant and palliative settings.1 2 These treatments can elicit immune-related adverse events (irAEs)3 4 including myositis and myocarditis—although the occurrence of these particular toxicities is very rare, being observed in <1% of cases with fatalities reported in <0.01% of recipients of anti-PD-1 alone.5 6