Congenital Myasthenic Syndromes

Treatment

Treatment depends on the form of congenital myasthenic syndrome (CMS). Drugs used to treat one form of CMS may be harmful if used to treat a different form.

Although CMS shares many symptoms with myasthenia gravis, CMS is a congenital disease, not an autoimmune disease, so it won't respond to immunosuppressant drugs or other therapies used to treat myasthenia gravis.

One form of presynaptic CMS is caused by an insufficient release of acetylcholine (ACh) and is treated with cholinesterase inhibitors.

Postsynaptic CMS is caused by by insufficient production of the ACh receptors or by receptors that don't stay open long enough (fast-channel CMS) or stay open too long (slow-channel CMS).

The fast-channel syndrome is treated with cholinesterase inhibitors and 3,4-diaminopyridine, drugs that increase the synaptic response to acetylcholine. The slow-channel syndrome is treated by quinidine or fluoxetine, which decrease the response to acetylcholine.

CMS caused by insufficient production of the ACh receptor is treated with cholinesterase inhibitors.

Another form of CMS is caused by a defect in rapsyn, a protein needed to concentrate the receptor of the neuromuscular junction; this type of CMS also responds to cholinesterase inhibitors and 3,4-diaminopyridine.

Synaptic CMS is caused by an acetylcholinesterase deficiency and has no effective drug treatment.