LAUSR

The coincidence of polymyositis and myasthenia gravis is rare and often only one of the two diseases is being diagnosed. We report the case of a 51 year old female patient in which myasthenia gravis (class IIIa, modified MGFA classification) was diagnosed four years after resection of an incidental thymoma (type AB, Masaoka St. I). The thymoma had been detected during the work-up of a chronic cough by CT thorax. Myasthenia gravis presented with muscle weakness, dysarthria and double vision that worsened in the evenings, typical electrophysiological findings and positive acetylcholine receptor- and titin-antibodies. In parallel, elevated creatine kinase and myopathic changes in electromyography were detected, whole-body FDG-PET-CT showed hypermetabolic areas in the skeletal muscles and consecutive muscle biopsy enabled the diagnosis of polymyositis. Treatment was initiated with pyridostigmine, methylprednisolone and azathioprine.