[Dermatomyositis with squamous cell carcinoma of the lungs secondary to nivolumab treatment: a case report].

A 74-year-old man was administered nivolumab to treat recurrent squamous cell carcinoma of the lungs. He developed fatigue, redness on the front of his neck, muscle weakness, and difficulty in swallowing after receiving the third course of nivolumab. Physical and neurological examinations showed proximal limb muscle weakness, periorbital erythema, and erythema of the front of his neck as well as fingers. Laboratory investigations revealed elevated serum CK and aldolase levels, and he was diagnosed with dermatomyositis. We initiated steroid pulse therapy and intravenous immunoglobulin therapy; however, he died of advanced lung cancer. Immune checkpoint inhibitor-induced neuromuscular disease is increasingly being observed in clinical practice. We report a rare case of dermatomyositis with squamous cell carcinoma of the lungs secondary to nivolumab treatment.