Myasthenia gravis

Abstract

Myasthenia gravis (MG) is included in this text because it is commonly associated with thymic pathology, and thymic surgery remains an important component in the management of patients with MG. MG can be inherited or acquired, but the genetic forms are rare and not associated with thymic pathology, so will not be considered here. The clinical features, patho-physiology and management of acquired MG will be described, with particular reference to the importance of the thymus. Myasthenia Gravis is a prototype autoimmune disease, and is one of the best understood antibody-mediated disorders, with both the antigen (the acetylcholine receptor, AChR)) and pathogenic antibody having been identified more than 30 years ago. The characteristics of the antibodies and the mechanisms by which they cause the symptoms and signs of MG have been thoroughly elucidated. The association between thymic abnormalities and MG has been recognised for more than a century, with the earliest description probably being that of Lacquer, who described a patient with MG and a thymic tumour [1]. It was soon recognised that patients with MG could also have an enlarged or hyperplastic thymus, and in 1917 Bell suggested that 50% of patients with MG had an abnormal thymus [2]. Current estimates are that 10% of patients with MG have a thymic tumour (thymoma) and 30% have a hyperplastic thymus, while 10% of patients with thymomas have MG. © Springer-Verlag Berlin Heidelberg 2007.