Clinical and Immunological Comparisons in Patients with Myasthenia Gravis

Clinical manifestations in different immunological subtypes of myasthenia gravis may vary. Immunological and clinical comparisons are presented in separate publications, which are controversial and require further study. The determination of the immunological subtype of myasthenia gravis and the comparison with clinical manifestations might be used as markers for predicting of the course of myasthenia and can be useful for treatment optimization. The purpose of this work was to study the main clinical manifestations in patients with myasthenia gravis depending on the immunological subtype of the disease. Materials and methods. Neurological examination and determination of antibodies to acetylcholine receptors and / or antibodies to muscle-specific tyrosine-kinase in plasma were performed. The immunological data, depending on the clinical form of myasthenia gravis and the age of the onset of the disease were analyzed. Results and discussion. 96 patients (56 women and 40 men) with myasthenia gravis were involved into the study conducted from 2014 to 2016. There were 71 patients with generalized and 25 with ocular form of myasthenia gravis. The average age of patients was 50.5 ± 12.4, the mean duration of the disease was 4.4 ± 1.2 years. Antibodies to acetylcholine receptors were detected in 57 (80.3%) out of 71 patients with generalized form and in 13 (52.0%) out of 25 patients with ocular form of myasthenia gravis. According to our study, in 6 (8.5%) patients with generalized myasthenia gravis, antibodies to muscle-specific tyrosine-kinase were detected. In the case of an ocular form, these antibodies were not detected at all. In 8 (11.3%) patients with a generalized form of myasthenia gravis and in 12 (48.0%) patients with ocular form antibodies were not detected. These patients can be attributed to the seronegative type of myasthenia gravis. The main clinical manifestations in patients with ocular myasthenia are ptosis and ophthalmoplegia, while there is no significant difference in occurrence of these manifestations in patients depending on presence or absence of antibodies to acetylcholine receptors. Patients with a generalized form of myasthenia gravis with presence of antibodies to acetylcholine receptors, both with an early onset and with late one, had generalized muscle weakness and fatigue as dominant clinical presentation. In contrast, in patients with a generalized form of myasthenia associated with antibodies to muscle-specific tyrosine-kinase, the main clinical signs were the weakness and fatigue of orofacial muscles. Predominance of eye manifestations in patients with seronegative type of myasthenia gravis might be explained by the fact that this type of disease is found to be 4.5 times more frequent in patients with ocular myasthenia gravis in comparison to the generalized myasthenia gravis. Conclusions. The main immunological subtype of myasthenia gravis, regardless of age, is the myasthenia associated with antibodies to acetylcholine receptors (detected in 80.3% of patients), with generalized muscle weakness and fatigue as predominant clinical manifestations. Myasthenia associated with antibodies to muscle-specific tyrosine-kinase is relatively rare condition (8.5% of patients with generalized myasthenia), does not depend on the age of the onset of the disease, its main manifestations are the weakness of orofacial muscles. In patients with ocular myasthenia, only antibodies to muscle-specific tyrosine kinase (52% of patients) were detected, and the main clinical manifestations are ptosis and ophthalmoplegia. In 20.8% of patients neither antibodies to acetylcholine receptors nor to muscle-specific tyrosine kinase have been detected (seronegative form), ptosis and ophthalmoplegia are predominant in the clinical picture in these patients.