The introduction of immune checkpoint inhibitors (ICIs) has deeply changed the management and prognosis of patients with metastatic melanoma (MM) over the past decade, unleashing T cells’ ability to mediate antitumor responses by targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death-1 (PD-1) signals [1,2]. The gene discussed is CTLA4; the disease is Miyoshi myopathy.