UniProtKB/Swiss-Prot

Myasthenic syndrome, congenital, 3B, 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. CMS3B 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, 3b, Fast-Channel, is also known as cms3b, and has symptoms including ophthalmoplegia, high palate and ptosis. An important gene associated with Myasthenic Syndrome, Congenital, 3b, Fast-Channel is CHRND (Cholinergic Receptor Nicotinic Delta Subunit).

Disease Ontology

A congenital myasthenic syndrome characterized by autosomal recessive inheritance of postsynaptic neuromuscular junction defects resulting in rapid decay in endplate current and a failure to reach the threshold for depolarization and early onset progressive muscular weakness that has material basis in homozygous or compound heterozygous mutation in the CHRND gene on chromosome 2q37.

OMIM

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 acetylcholine receptor 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). (616322)