[Congenital myasthenic syndrome]

Congenital myasthenic syndromes (CMS) are rare heterogeneous disorders in which neuromuscular transmission is compromised by one or more specific mechanisms. CMS are clinically diagnosed by a history of fatigability and muscle weakness since infancy or early childhood, a decremental EMG response and the absence of acetylcholine receptor antibodies. CMS form a heterogeneous group of disorders which are classified as originating from presynaptic, synaptic or postsynaptic defects. Molecular genetic studies reveal a various type of mutations in synapse-associated genes. However, the genetic abnormalities of many CMS are still unresolved. This article outlines the classification of CMS and etiology of individual forms.