Nivolumab-Induced Polymyalgia Rheumatica in a Patient with Lung Adenocarcinoma

A 79-year-old woman was diagnosed with stage IV (cT1aN1M1, OSS) lung adenocarcinoma with bone metastasis of the right femur. She received nivolumab as a third-line treatment. She developed pain in the right shoulder, left wrist, right knee, and waist as well as a low-grade fever and morning stiffness, after five courses of nivolumab. After closer examination, she was diagnosed with polymyalgia rheumatica (PMR) precipitated by an immune-related adverse event. Nivolumab was discontinued, and oral prednisolone was started. Her arthralgia improved. Caution should be exercised regarding the development of PMR when polyarthralgia occurs during nivolumab treatment in patients with lung cancer.