Epidemiology

• antibodies to acetylcholine (ACh) receptors (AChRs) themselves occur in 85% of cases ('seropositive'); in the remainder of cases antibodies bind to a different muscle membrane target ('seronegative')
• prevalence in northern Europe is 10-15 per 100,000
• non-thymoma cases have a peak incidence at 10-30 years and again, at 60-70 years of age; those associated with thymoma have a peak incidence at 40-50 years of age
• females are affected more often in the under 40 year old age group whereas men predominate in cases which develop in older age groups
• about 10% of cases develop during childhood
• thymoma - this is present in 10% of patients but is rare in 'seronegative' myasthenia gravis and children

Reference:

1. Jayam Trouth A, Dabi A, Solieman N, Kurukumbi M, Kalyanam J. Myasthenia gravis: a review. Autoimmune Dis. 2012;2012:874680
2. Deenen JC, Horlings CG, Verschuuren JJ, et al. The epidemiology of neuromuscular disorders: a comprehensive overview of the literature. J Neuromuscul Dis. 2015;2(1):73-85.