Dermatomyositis associated with invasive thymoma

We report a case of dermatomyositis (DM) associated with invasive thymoma i n a 22-year-old woman who was admitted to our hospital complaining of dyspn ea which required ventilation support, The reddened elevated scaly eruption s were prominent over the extensor surfaces. Chest X-ray and computed tomog raphy showed mediastinal masses, which were diagnosed as mixed type thymoma , Muscle and skin biopsy specimens were compatible with DM, She was treated with methylprednisolone pulse therapy followed by extended removal of the anterior mediastinal tumor and subsequent radiotherapy. She has had a good clinical course without recurrence of thymoma or DM for more than 3 years. The role of thymoma in the development of DM is discussed.