Disease coordinator for Neuromics: Hanns Lochmüller
Congenital Myasthenic Syndromes (CMS) is the name for a group of inherited disorders of the neuromuscular junction which have certain clinical and genetic features in common. Muscle weakness is common in CMS, but highly variable from hour to hour, day to day or month to month. CMS is a rare condition with approximately 1 patient in 150,000 people world-wide.
First symptoms of CMS usually occur in children before the age of 3 years. In infancy floppiness, poor suck and cry, choking spells, breathing difficulties and hanging eye lids (ptosis) are frequently observed. Symptoms worsen by crying or activity. Children often show delayed motor milestones and may have difficulty running. Breathing difficulties can become very severe in some patients requiring assisted ventilation.
The inheritance of CMS is autosomal recessive in the majority of patients. This means that both parents are usually unaffected, but pass on a defective copy of the CMS gene to their affected child. CMS genes code for proteins that are involved in neuromuscular transmission, the process involved in transmitting signals from the nerve endings to the muscle. This is a crucial step in relaying the signals to muscles to contract or relax. Drugs that influence neuromuscular transmission can result in clear improvement in patients with CMS and finding a genetic diagnosis helps to select the appropriate medication for each patient.
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