Clinical and biological heterogeneity of autoimmune myasthenia gravis.

Although myasthenia gravis (MG) has long been considered a well-established autoimmune disease associated with autoantibodies, which are convincingly pathogenic, accumulating data indicate both clinical and biological heterogeneity similar to many other putative autoimmune disorders. In a subset of patients, thymus plays a definite role: thymic autoimmunity results in generation of autoantibodies within the thymus, which cross-react with antigens at the neuromuscular junction, or thymoma leads to deficient central tolerance and impaired T cell selection. Heterogeneity on the autoantibody level may be associated with genetic heterogeneity and clinical phenotypes with different treatment responses.