Myasthenic Syndromes, Congenital

Congenital myasthenic syndromes (CMSs) represent a heterogeneous group of disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiological, and morphological studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region of the motor endplate. The disease proteins identified to date include choline acetyltransferase, the ColQ component of acetylcholinesterase, β2-laminin, agrin, each subunit of the acetylcholine receptor, rapsyn, muscle specific kinase, and Na_v1.4, downstream of tyrosine kinase 7, and glutamine-fructose-6-phosphate transaminase 1. Analysis of electrophysiological and biochemical properties of mutant proteins expressed in heterologous systems contributed crucially to defining the molecular consequences of the observed mutations and resulted in improved therapy of most CMSs.