Myasthenia gravis

Abstract

Myasthenia gravis (MG) is an autoimmune condition affecting the neuromuscular junction. MG may affect patients at any age. The juvenile version makes up 10% of MG, and the adult version has a bimodal distribution with peaks around age 30 and 50 years. Annual incidence ranges from 5 to 30 cases per million person-years, and prevalence ranges from 10 to 20 cases per 100,000. Ocular involvement may occur in 75%, and the ocular-only form makes up 20% of MG. Ocular symptoms include ptosis and diplopia that is often asymmetric, variable, and fatigable with symptoms worse in the evening. MG is thought to be an antibody-mediated disease, although recent research shows a significant role for complement activation and the membrane attack complex. Autoantibodies including anti-acetylcholine receptor and muscle-specific kinase antibodies are found in 85% of generalized MG but only are detected in approximately 50% of ocular MG. While there are treatment guidelines for systemic MG, there is limited evidence to guide treatment for ocular myasthenia.