[A retrospective group study on post-thymectomy myasthenia gravis]

Retrospective group study on post-thymectomy myasthenia gravis (post-Tm MG) was carried out. Five hundred and twenty-seven resected thymoma cases (133 cases with MG and 394 cases without MG) were collected from 9 hospitals. Post-Tmx MG occurred in 18 out of 394 cases -4.6% of thymoma without MG-, and these 18 patients with post-Tmx MG were investigated retrospectively. As to surgical procedures, the mode of operation, either thymectomy or thymo-thymectomy was not thought to be an important factor in the pathogenesis of post-Tmx MG. These 18 patients could be divided into 7 with early onset and 11 with late onset. In the early onset group, post-Tmx MG occurred within 6 months after the operation, and these 7 patients may have had subclinical MG at the time of the initial operation. In the late onset group, post-Tmx MG was noted in 5 patients when recurrence of the tumor was confirmed, the latest being 11 years after operation. The pathogenesis of post-Tmx MG could not be clarified in the other 6 patients (33.3%). For further evaluation of these 6 cases, a prospective studies with large scale are needed.