Mijastenija gravis poznog životnog doba - poseban klinički entitet

The acquired autoimmune myasthenia gravis (AAMG) is an autoimmune disease of neuromuscular junction which is characterized by bimodal appearance of the disease. In the first peak of the disease between 20 and 30 years of age, there is female predominance, whereas in the second peak both sexes are equally attacked by the disease. The aim of this study is to present the demographic, clinical and histological features of the late onset of myasthenia gravis in order to identify possible specific features of this type of disease and contribute to improved understanding of its pathogenesis and thus to the improvement of diagnostics and treatment of these patients. A retrospective analysis of 272 patients treated at the Institute of Neurology KCS in Belgrade was carried out in the period 1984-2003. The sample included 167 male (61.4%) and 105 female (38.6%) patients, which shows that the male patients were predominant in the 1.6:1 ratio. The IIB form appeared to be the most frequent clinical presentation of the late onset of myasthenia gravis. The initial symptoms in 190 patients (69.9%) were ptosis or double vision. In the following two year period the disease was generalized in 68.9% patients. The provoking factor was observed in every fourth patient (23.5%), most frequently stress or respiratory infection. In 159 patients (58.5%) the course of the disease was favorable (remission or improvement) while in the rest of the patients the condition at the end of the observed period was either unchanged or worsened. Thymectomy was very rarely performed in older patients group, in only 15.8%. The histological analysis in half of patients (51.1%) showed persistent or atrophic thymic tissue, while in the rest (48.9%) there was thymic hyperplasia. Patients with thymoma were not included in the study. As regards the parameters analyzed, conclusion may be drawn that the late onset of myasthenia gravis is characterized by the predominance of male patients, by the rare presence of the provocative factor, by frequent ocular symptoms in the initial stage of the disease, by the high percent of generalization and high frequency of grave clinical picture and less favourable course of the disease. As regards the thymic pathology, the thymic hiperplasia is significantly rarer which suggests a lesser importance of thymus as a possible trigger of the late onset of myasthenia gravis. These specific features of the late onset of myasthenia gravis suggest that this form of disease may be regarded as a separate clinical entity within AAMG.