Congenital myasthenic syndromes are a group of conditions that are characterized by weak muscles that tire easily (myasthenia). In people with these conditions, myasthenia typically begins shortly after birth or during early childhood. The most commonly affected muscles are the muscles in the head and neck (bulbar muscles) that control chewing and swallowing, speech, and facial expressions; the muscles that move the eyes and eyelids; and the muscles in the arms and legs. However, any of the muscles used for movement (skeletal muscles) can be affected.

Variants (also called mutations) in more than 35 genes can cause congenital myasthenic syndromes. Variants in the CHRNE gene are responsible for about half of all cases. Variants in the COLQ and DOK7 genes are responsible for 20 to 30 percent of all cases. Variants in other genes are each responsible for a small percentage of cases.

The prevalence of congenital myasthenic syndromes is estimated to be 2 in 1 million individuals worldwide. In people under 18 years of age, the prevalence is estimated to be 10 in 1 million individuals.

Congenital myasthenia syndromes are usually inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorders. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the conditions.

Published Date: February 13, 2026
Published By: National Institutes of Health