T cell lymphocytosis associated with polymyositis, myasthenia gravis and thymoma

Peripheral T cell lymphocytosis is a rare finding in association with malignant thymomas. In the majority of previous cases, the tumours have behaved aggressively with symptoms arising from local invasion. We describe a patient with ocular myasthenia gravis who presented with a rapidly progressive polymyositis and neuropathy and who was subsequently found to have a thymic mass and a mild T cell lymphocytosis. The thymoma did not give rise to local symptoms and showed no evidence of progression over a 14-month period of follow-up. The possibility of an underlying thymic tumour should be considered in any patient with chronic T cell lymphocytosis if the circulating cells show mature morphology and there is no molecular evidence of monoclonality.