About Congenital Myasthenic Syndrome

Congenital myasthenic syndromes (CMS) are inherited muscular disorders resulting from genetic flaws at the neuromuscular junction, where the nerve and muscle cells communicate.

CMS is categorized by the part of the neuromuscular junction affected:

• Presynaptic (the nerve cells)
• Postsynaptic (the muscle cells)
• Synaptic (the space between the nerve and muscle cells)

Presynaptic CMS symptoms commonly include episodic apnea (CMS-EA), where breathing stops briefly. Other symptoms include weakness of the eye, mouth and throat muscles, sometimes resulting in double vision and difficulty chewing or swallowing.

Postsynaptic CMS symptoms can range from mild to severe. Symptoms in infancy include severe muscle weakness, feeding and respiratory problems, and delays in motor milestones such as sitting, crawling and walking. Childhood or adult onset symptoms may include difficulty raising the eyelids (ptosis) and fatigue, but usually they don’t interfere with daily living.

In one form of postsynaptic CMS (slow-channel CMS), severe weakness that begins in infancy or childhood can progress and lead to loss of mobility and respiratory problems in adolescence or later in life.

Synaptic CMS symptoms commonly include feeding and respiratory problems early in childhood and weakness causing delayed motor milestones, reduced mobility and curvature of the spine (scoliosis).

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