Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ) hallmarked by fatigable muscle weakness. The disease fulfills all of the Witebsky postulates and is a classic example of an antibody-mediated autoimmune disease. Autoantibodies are produced against proteins involved in neuromuscular transmission or in the development and maintenance of the NMJ. The antibodies against the acetylcholine receptor exert their function by activation of the classical complement pathway, by antigenic modulation and internalization of the receptor or by direct block of function, thus fulfilling category II and V of the Gell and Coombs classification. Autoantibodies against muscle-specific kinase block protein-protein interaction and signal transduction at the synapse. In many forms of MG, the thymus plays a crucial role in the pathogenesis, including thymoma or thymic hyperplasia, with ectopic germinal centers, including antigen-specific long-lived plasma cells. Genetic factors may contribute to a predisposition for developing MG. Therapeutic options include acetylcholinesterase inhibitors and immunosuppression, in early-onset MG thymectomy is advisable. In case of myasthenic crisis, plasmapheresis or intravenous immunoglobulin is indicated.