Malignant Peritoneal Mesothelioma Presenting with Polymyalgia Rheumatica-like Syndrome.

A 30-year-old man was admitted to our hospital because of pain in his proximal extremities. The pain mimicked polymyalgia rheumatica (PMR) and it temporarily improved by a low dose of glucocorticoids, but his symptoms relapsed many times. After six years of glucocorticoid treatment, he developed abdominal pain and ascites, for which he was diagnosed with malignant peritoneal mesothelioma (MPM).