Congenital myasthenic syndromes are genetic disorders of the neuromuscular junction (NMJ) that are classified by the site of the transmission defect: presynaptic, synaptic, and postsynaptic. CMS8 is an autosomal recessive disorder characterized by prominent defects of both the pre- and postsynaptic regions. Affected individuals have onset of muscle weakness in early childhood; the severity of the weakness and muscles affected is variable. [From OMIM]