[The morphological and clinico-immunological characteristics of 2 types of myasthenia]

The thymus is studied morphologically in 139 cases of myasthenia (with no thymic neoplasia). Hyperplasia of true thymic parenchyma (without its intralobular perivascular spaces) was observed in 28%, no change in 40% and atrophy in 32% of cases. Two types of the disease were distinguished on the basis of morphological and clinico-immunological parameters: the 1st type with a hyperplastic or normal thymic parenchyma and the 2nd type with its atrophy. These types probably differ in their pathogenesis. The outcome of the thymectomy in patients with the 1st type of myasthenia is most favourable, while in patients with the 2nd type the outcome in 42% of patients is either satisfactory or unfavourable.