[Polymyositis associated with thymoma].

Neuromuscular diseases accompanying thymoma include myasthenia gravis, polymyositis, dermatomyositis, and neuromyotonia. Usually 50% of patients with thymoma develop myasthenia gravis. However, only 5% show polymyositis as an accompanying paraneoplastic phenomenon. We report the case of a patient with thymoma showing myasthenia gravis as well as polymyositis. Due to the simultaneous occurrence of these paraneoplastic diseases, the criteria for exact diagnosis (serum creatine kinase, EMG, ocular involvement) overlap. This diagnostic dilemma can appreciably complicate the therapeutic approach.