Increasing incidence of myasthenia gravis among elderly in British Columbia, Canada

Abstract

Presence of anti-acetylcholine receptor (anti-AChR) antibodies is highly specific for myasthenia gravis (MG). These antibodies are detected in 85%–95% of sera from patients with generalized MG and 40%–70% of patients with ocular MG.1 An increasing incidence of MG, especially in the elderly population, has been described in Japan, the United Kingdom, and Denmark.2,–,4 Recent studies have also focused on the epidemiology of anti-AChR antibody seropositivity as a surrogate marker of MG.4,–,6 The Neuro-Immunology Laboratory at the University of British Columbia is the sole laboratory in British Columbia (BC), Canada, offering anti-AChR antibody testing for clinical diagnosis. The aims of this study were to evaluate the incidence and epidemiologic characteristics of anti-AChR antibody seropositivity in BC and to examine changes in incidence over time. ### Methods. We performed a population-based study of the incidence of anti-AChR antibody-seropositivity in BC for the 25-year period of January 1, 1984, to December 31, 2008. Incident cases were ascertained by retrospectively identifying all first-time seropositive tests. A positive anti-AChR antibody test …