Immune checkpoint inhibitors (CPI) targeting the programmed death 1/programmed death-ligand 1 (PD-1/PD-L1), as well as the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), have demonstrated promising and durable antitumor activity, and revolutionized the treatment of metastasized malignant melanoma (MM) patients1–3. Here, CTLA4 is linked to Miyoshi myopathy.