The anti-PD-1 antibodies pembrolizumab and nivolumab have been approved for the treatment of several advanced malignancies, including malignant melanoma (MM)1,2 and non-small-cell lung cancer (NSCLC).3,4 In addition to their antitumour effects, ICIs have been reported to cause characteristic adverse events, called immune-related adverse events (irAEs),5 in the lung, skin, gastrointestinal tract, liver and endocrine glands. The gene discussed is PDCD1; the disease is Miyoshi myopathy.