Prevalence of myasthenia gravis in the Catalan county of Osona

Introduction: The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65 years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65. Methods: The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991. Results: The prevalence of myasthenia gravis was 32.89 x 10(5) inhabitants (95% CI, 23.86-41.91). The standardized prevalence (European population) was 35.47 x 10(5) inhabitants (95% CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25 years old, prevalence was 21.87 x 10(5) in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35 x 10(5). The clinical characteristics prior to treatment and at the cut-off date are similar (P> .05) in patients younger than 65 and those aged 65 and older. Conclusions: These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly population. (C) 2014 Sociedad Espanola de Neurologia. Published by Elsevier Espana, S.L.U. All rights reserved.