SNP Shot: Genomic Insights

Congenital myasthenic syndromes (CMS) encompass a collection of disorders that cause muscle weakness (myasthenia). This weakness is exacerbated by physical activity. While it often manifests in early childhood, onset can occur later, during adolescence or even adulthood. The muscles of the face are frequently affected, including those controlling the eyelids, eye movements, chewing, and swallowing. However, any skeletal muscle can be involved. Infants with CMS may struggle with feeding due to muscle weakness, and motor skill development, such as crawling and walking, may be delayed. The degree of muscle weakness varies considerably; some individuals experience mild weakness, while others suffer from debilitating weakness that prevents them from walking.

Some individuals may experience breathing difficulties, sometimes triggered by fever or infection. In severe cases, individuals may also have short periods of stopped breathing (apnea), potentially leading to a bluish discoloration of the skin or lips (cyanosis).

Inheritance:

CMS typically follows an autosomal recessive inheritance pattern. This means that an individual must inherit two copies of a mutated gene, one from each parent, to develop the condition. The parents are carriers, each possessing one copy of the mutated gene, but usually without exhibiting symptoms. In rare instances, CMS is inherited in an autosomal dominant manner. In this case, only one copy of the altered gene is needed to cause the disorder. An affected person may inherit the altered gene from an affected parent, or the condition may result from a new gene mutation in an individual with no family history of CMS.