[Myositis as differential diagnosis in polymyalgia rheumatica].

An 82-year-old man was diagnosed with polymyalgia rheumatica. Rapid improvement was achieved after peroral prednisolone administration. Two years later while being treated with low-dose prednisolone, the acute phase reactants increased, now also with proximal muscle weakness, weight loss and elevated muscle enzymes. Needle biopsy confirmed dermatomyositis. Polymyalgia rheumatica is a common disease among the elderly. It has several differential diagnoses including dermatomyositis and polymyositis.