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Few cohort epidemiologic myasthenia gravis (MG) studies have been published,1,2 most of them with data from multiple databases and varying inclusion criteria. A review from 1996 reported an increasing MG incidence and prevalence.3 Studies from the last 10 years refer to a yearly incidence between 4 and 11 per million1,2,4 and a prevalence ranging from 70 to 150 per million.1,2,4,5 There is only one laboratory in Norway offering acetylcholine receptor (AChR) antibody testing and all samples are sent to this laboratory. Presence of AChR antibodies is nearly 100% specific for MG in individuals with symptoms.6 The aims of this study were to determine the incidence and prevalence of AChR antibody-positive (seropositive) MG, to describe its gender-specific characteristics, and to examine epidemiologic trends during the last decades. ### Methods. Norway had a population of 4,737,171 inhabitants on January 1, 2008, our chosen MG prevalence day (Statistics Norway-SSB, www.ssb. no). Since the start of our AChR antibody …
Heldal et al. (Mon,) studied this question.