Juvenile myasthenia gravis may be more common than believed

A rare form of myasthenia gravis that manifests in childhood and adolescence called juvenile myasthenia gravis (JMG) affects roughly 30 out of every 1 million children in the U.S., and may be more common than previously thought, a study estimates.

The study also found that JMG is more common among girls than boys, and in Black children over white children.

“Understanding the incidence and prevalence of JMG is crucial for optimizing its management. Therefore, the findings from this comprehensive evaluation significantly contribute to the expanding knowledge of the demographic characteristics of the JMG population,” the researchers wrote. The study, “Incidence and Prevalence of Juvenile Myasthenia Gravis in the United States Between 2010 and 2020: Analysis of Two Claims Databases,” was published in Neurology and Therapy. 

Myasthenia gravis is an autoimmune disease that causes problems with the communication between nerve and muscle cells, resulting in muscle weakness and fatigue. It usually manifests in adulthood, but in JMG, symptoms arise during childhood or adolescence.

Rates of JMG higher than believed

There isn’t much data on how common JMG is, or how the disease’s prevalence varies by sex or ethnicity. To get a better idea, the researchers analyzed two U.S. insurance databases, reviewing data from 2010 to 2020. One database gathered information from commercial insurance companies, while the other used data from Medicaid, the government-run program that provides health insurance to low-income Americans.

The overall prevalence of JMG in 2020 was 25.3 out of every 1 million children in the commercial database and 37.6 out of every million in the Medicaid database, with minimal variation from year to year. The incidence of the disease, or the number of newly diagnosed cases each year, showed some fluctuations from year to year, but there wasn’t any obvious pattern or trend in the rates of new cases.

The rates are somewhat higher than previous estimates, meaning “the burden of JMG might have been underestimated,” the researchers wrote.

JMG is more common in older children and teens than in younger kids, the data suggest. The disease’s prevalence in 2020 was up to two times higher in girls compared with boys in the two databases.

The prevalence of JMG in Black children was up to 3.4 times higher than in white children, the Medicaid database showed. The commercial database didn’t include information on race, so it could not be included in the analysis.

“We found incidence and prevalence to be markedly higher in girls and Black people under 18,” the researchers wrote. “The data from this large population study reveal that age, race/ethnicity, and sex collectively may influence JMG occurrence.”