Myasthenic Syndrome, Congenital, 4b, Fast-Channel (CMS4B)

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OMIM 57 616324 Disease Ontology 12 DOID:0110677 MedGen 42 C4225369 CN229752

MeSH 44 D020294 SNOMED-CT via HPO 69 258211005 11934000 16110005 205294008 409623005 248268002 193093009 95666008 78164000 more

UniProtKB/Swiss-Prot : ⁷⁵ Myasthenic syndrome, congenital, 4B, fast-channel: A form of congenital myasthenic syndrome, a group of disorders characterized by failure of neuromuscular transmission, including pre- synaptic, synaptic, and post-synaptic disorders that are not of autoimmune origin. Clinical features are easy fatigability and muscle weakness affecting the axial and limb muscles (with hypotonia in early-onset forms), the ocular muscles (leading to ptosis and ophthalmoplegia), and the facial and bulbar musculature (affecting sucking and swallowing, and leading to dysphonia). The symptoms fluctuate and worsen with physical effort. CMS4B is a fast-channel myasthenic syndrome. It is caused by kinetic abnormalities of the AChR, resulting in brief opening and activity of the channel, with a rapid decay in endplate current, failure to achieve threshold depolarization of the endplate and consequent failure to fire an action potential.

MalaCards based summary : Myasthenic Syndrome, Congenital, 4b, Fast-Channel, also known as cms4b, is related to myasthenic syndrome, congenital, 4a, slow-channel and congenital myasthenic syndrome. An important gene associated with Myasthenic Syndrome, Congenital, 4b, Fast-Channel is CHRNE (Cholinergic Receptor Nicotinic Epsilon Subunit). Related phenotypes are ptosis and respiratory insufficiency

Disease Ontology : ¹² A congenital myasthenic syndrome characterized by autosomal recessive inheritance of postsynaptic neuromuscular junction defects, early-onset progressive muscle weakness, and kinetic abnormalities of the AChR channel that has material basis in homozygous or compound heterozygous mutation in the CHRNE gene on chromosome 17p13.

OMIM : ⁵⁷ Fast-channel congenital myasthenic syndrome (FCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the AChR channel, specifically from abnormally brief opening and activity of the channel, with a rapid decay in endplate current and a failure to reach the threshold for depolarization. Treatment with pyridostigmine or amifampridine may be helpful; quinine, quinidine, and fluoxetine should be avoided (summary by Sine et al., 2003 and Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). (616324)

Clinical features from OMIM:

616324

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