A population-based legacy study of myasthenia gravis in Iceland: insights from a small Arctic nation

Myasthenia gravis (MG) is a rare autoimmune neuromuscular disorder for which population-based estimates remain scarce, particularly in small, homogeneous settings. Leveraging Iceland's centralized healthcare, we reassessed MG epidemiology and clinical features in a nationwide legacy cohort. Cases diagnosed from 1981 to 2002 were identified through hospital databases, private neurologists, immunology laboratory records and the national MG association. Inclusion required characteristic symptoms plus at least one confirmatory test (response to acetylcholinesterase inhibitors, abnormal electrophysiology, or positive antibodies). Point prevalence was calculated on 31 December 2002, and incidence for 1997-2002. In 2003, patients were evaluated to document diagnostic delay, treatment patterns and disease severity; descriptive statistics and non-parametric tests were applied. Twenty-six patients met criteria, yielding a prevalence of 9.0 per 100,000 and a mean annual incidence of 0.78 per 100,000. The female-to-male ratio was 1.2:1; mean age at onset was 43 years overall (29 in women, 59 in men). Ocular symptoms predominated at presentation. Nineteen percent experienced diagnostic delays exceeding three years. By 2003, 54% had generalized MG and 27% were in complete remission off medication. This historical cohort aligns with global trends of rising prevalence and illustrates the value of legacy datasets for rare disease surveillance.