Abstract
The prevalence and incidence of myasthenia gravis (MG) have increased over the years, especially in elderly men. Current estimates are 0.17–1.04/100,000 for incidence and 0.3–20/100,000 for prevalence. Antibodies against the acetylcholine receptor (AchR-Ab) are found in approximately 80%. Antibodies against muscle-specific kinase (MuSK-Ab) occur in 1–10% of patients, most commonly women, while antibodies against low-density lipoprotein receptor-related protein 4 (LRP4-Ab) are found in 7–33% of double-seronegative patients. Coexisting autoimmune diseases are frequent in MG, with autoimmune thyroid disease being the most common. Thymoma or a hyperplastic thymus can be found in AchR-Ab-positive MG. Thymectomy is mandatory in thymoma and recommended in AchR-Ab-positive generalized MG between 18 and 65 years of age. Despite immunosuppressive treatment 10–20% remain treatment-refractory. Eculizumab, a complement inhibitor, has recently been approved for treatment-refractory cases. Congential myasthenia is rare, but treatments exist and depend on the underlying genetic defect. The Lambert–Eaton myasthenic syndrome (LEMS) is commonly secondary to small cell cancers, particulary lung. Seventy-five percent of patients with LEMS have antibodies to voltage-gated calcium channels. LEMS can also be idiopathic with no know cause. 3,4-Diaminopyradine is now approved for the treatment of LEMS.
Contributions by Wolfgang N. Löscher
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Feldman, E.L., Russell, J.W., Löscher, W.N., Grisold, W., Meng, S. (2021). Neuromuscular Transmission: Endplate Disorders. In: Atlas of Neuromuscular Diseases. Springer, Cham. https://doi.org/10.1007/978-3-030-63449-0_13
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