Left atrial myxoma detected after an initial diagnosis of polymyalgia rheumatica.

We herein report the case of a 69-year-old woman with left atrial myxoma detected following treatment with glucocorticoids for an initial diagnosis of polymyalgia rheumatica (PMR). The glucocorticoids markedly improved the patient's symptoms, and the tumor was excised after rapidly tapering the glucocorticoid dose. The PMR-like symptoms did not recur and the inflammatory marker levels returned to normal after surgery. The patient's clinical course indicated that the initial PMR-like symptoms were entirely caused by the left atrial myxoma. This case demonstrates that glucocorticoid treatment for suspected PMR can mask the symptoms of myxoma, leading to a delay in diagnosis.