Myasthenia gravis Anterior horn cell disease

Abstract

Myasthenia gravis is a rare condition. Perhaps as a consequence, there is sometimes considerable delay before the diagnosis is established. In some patients, the disorder is confined, at least clinically, to the ocular muscles, resulting in ptosis and diplopia. If this localization persists for two years, the condition is unlikely then to become generalized. Myasthenia may also present with generalized muscle weakness and fatiguability, sometimes in a fulminating fashion. Reversal of weakness by intravenous injection of edrophonium (Tensilon) supports the diagnosis but a small proportion of myasthenic patients (perhaps 5–10%) fail to respond [1]. There is an association between myasthenia and various auto-immune disorders, including pernicious anaemia and thyroid disease. Myasthenic patients have an increased incidence of thymic hyperplasia and some 10% are found to have a thymoma. Younger myasthenic patients, without thymoma, have a higher incidence of HLA antigens A1, B8 and DRW3, whereas in older patients (over 40 years) without thymoma, the association is with A3, B7 and DRW2 [2].