Thymoma and Hemopoietic Insufficiency

The association of thymic neoplasms with myasthenia gravis is well recognized. A thymoma has been encountered in approximately one-fourth of the patients with this disorder, and a large number exhibit microscopic evidence of hyperplasia of this structure.1More than 50% of thymic neoplasms have occurred in persons with myasthenia gravis.2The exact relationship of this association is baffling. Resection of a thymoma in patients with this disorder has resulted in the alleviation of its clinical manifestations in some but not all instances, and examples of myasthenia gravis developing after the removal of such a tumor have accumulated in the literature.3One of the cases reported by Fisher, Coburn, and Effler4was unique in that the development of a thymoma provided relief from the symptoms of myasthenia gravis which had been present for 13 years. In recent years attention has been directed to the occurrence of thymic