Epidemiology of myasthenia gravis.

MG epidemiology may provide clues to disease etiology and pathogenesis. It is crucial for health planning and to estimate societal needs for health care resources. Recent high-quality studies have found an annual MG incidence of approximately 20 per million person-years, and a prevalence of approximately 25 per 100,000 population. Geographical variation reflects differences in case finding and diagnostic tools, but also a multitude of genetic and environmental etiological and risk factors. MG prevalence has increased in recent years because of more elderly people in the general population, improved case finding, and improved MG treatment with reduced mortality. In populations with optimal treatment, there is only a slightly increased mortality risk with MG. There are marked variations among MG disease subgroups regarding epidemiology. MuSK MG is more common in the Mediterranean area, juvenile MG is most common in China, whereas late onset MG with AChR antibodies is a subtype that has increased in incidence and prevalence globally.