Prevalence and clinical aspects of immigrants with myasthenia gravis in northern Europe.

Introduction: Multiethnic studies can provide etiological clues toward the genetic and environmental influence of a disease. The aim of this study was to determine prevalence and clinical features of myasthenia gravis (MG) in immigrants compared with native patients in 2 population-based cohorts.

Methods: This cross-sectional study included 843 MG patients (375 from Norway and 468 from the Netherlands). Ethnic background was defined by questionnaires.

Results: Among the participating MG patients, 163 of 843 (19.3%) were first or second generation immigrants, mainly from Europe, Asia, and South America. No marked prevalence differences were found between immigrants and native ethnic groups. MG with muscle specific kinase antibodies and MG with thymoma were more frequent in Asian MG immigrants compared with other ethnic groups (8% vs. 0-4%; P < 0.001 and 21% vs. 6-10%; P < 0.001), respectively.

Conclusions: Our findings indicate that Asian immigrant MG patients carry genetic factors or environmental/lifestyle factors which contribute to their specific phenotype, even after migration. Muscle Nerve 55: 819-827, 2017.