[Thymus gland pathology in myasthenia gravis: cause or consequence?]

Analysis of the literature data and of the findings of histologic and immunohistochemical studies of operation biopsy specimens of the thymus obtained from 92 patients with myasthenia has demonstrated that abnormalities of the thymus are characteristic of myasthenia patients. In nontumor involvement of the thymus (84.7 percent of the examinees) these abnormalities present as thymic parenchyma involution of varying gravity, combined (in 54.3 percent of patients) with hyperplasia of intralobular perivascular cavities, this simulating the so-called thymic hyperplasia with lymphoid follicles. Furthermore, impaired expression of certain epitheliocytic antigens is detectable and changed counts of these cells subpopulations; thymic hormones hyperproduction occurs in young patients. In thymomas (15.3 percent of the examined myasthenia patients) the tumor epithelial cell subcortical and/or cortical antigens are intact, thymic hormones production is not always excessive, and disorders in some antigens expression are similar to those observed in nontumor involvement of the thymus. Thymic dysfunction appears to play the key role in the pathogenesis of autoimmune disturbances in myasthenia, and disordered activity of the epithelial cells and lymphoepithelial interactions may be the major factors here.