Congenital myasthenic syndrome

Congenital myasthenic syndrome is an inherited muscular disorder caused by genetic flaws at the neuromuscular junction. The effects of the disease are similar to Lambert-Eaton syndrome and Myasthenia gravis, the difference being that LEMS and MG are autoimmune disorders, but CMS is hereditary.

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Symptoms and categories

The types of CMS are classified into three categories: presynaptic, postsynaptic, and synaptic.

Presynaptic syptoms include brief stops in breathing, weakness of the eye, mouth, and throat muscles. These symptoms often result in double vision and difficulty chewing and swallowing. Postsynaptic symptoms in infants include severe muscle weakness, feeding and respiratory problems, and delays in the ability to sit, crawl, and walk. Onset symptoms for all ages may include droopy eyelids. A particular form of postsynaptic CMS (slow-channel CMS) includes severe weakness beginning in infancy or childhood that progresses and leads to loss of mobility and respiratory problems in adolescence or later life. Synaptic symptoms include early childhood feeding and respiratory problems, reduced mobility, curvature of the spine, and weakness, which causes a delay in motor milestones.

Treatment

Treatment depends on the form (category) of the disease. Although symptoms are similar to myasthenia gravis, treatments used in MG are not useful in CMS. MG is treated with immunosuppressants, but the effects of CMS are not caused by the immune system, it is hereditary.

A form of presynaptic CMS is caused by an insufficient release of acetylcholine (ACh) and is treated with cholinesterase inhibitors. Postsynaptic fast-channel CMS (ACh receptors do not stay open long enough) is treated with cholinesterase inhibitors and 3,4-diaminopyridine. Postsynaptic slow-channel CMS is treated with quinidine or fluoxetine, which plugs the ACh receptor. Synaptic CMS has no effective drug treatment.

References

• Myasthenia gravis, Lambert-Eaton Myasthenic syndrome & Congenital Myasthenic Syndrome
• About Congenital Myasthenic Syndrome From the Mayo Clinic website
• Treatment for Congenital Myasthenic Syndromes From the Mayo Clinic website

See also

• Congenital disorder
• Myasthenia gravis
• Lambert-Eaton syndrome