Thymomatous myasthenia gravis.

Abstract

The clinical course of 195 cases of myasthenia gravis was studied. Among them, 90 myasthenia patients received thymectomies, and of these, thirty cases of thymoma were pathologically proven. The incidence of thymomatous myasthenia gravis in these thymectomized patients was 33.3%. The average age of these 30 cases was 44.4±14.2 years and the sex ratio was almost equal. Their onset age was at 42.2±14.6 years. Before thymectomy, the clinical severity of 89.7% of thymoma patients were of a generalized type, especially typeⅡb, Ⅲ or Ⅳ. Compared with the two groups of thymic hyperplasia and hypoplasia, thymoma patients had a later onset with an equal sex distribution, and manifested a more severe myasthenia. The thymoma may be detected on radiological examination of the chest, especially by mediastinal CT scan. But in 16% of cases, the tumors were so small that they were found only after thymectomy. All patients underwent maximal thymectomy. The pathology of the thymus in these patients was predominantly of the lymph-epithelial type. Four cases (13.3%) were malignant thymoma and received radiation therapy after thymectomy. The histology of the tumor seemed to have no relationship to the severity of the myasthenia gravis. On follow-up of the showed improvement; 13.8% were in the state of remission; 65.5% showed improvement; 13.3% were unchanged and the mortality rate was 6.8%. Postoperative improvement was either immediate or gradual.