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Congenital myasthenic syndrome 7

Synonyms
MYASTHENIC SYNDROME, CONGENITAL, 7A, PRESYNAPTIC, AND DISTAL MOTOR NEUROPATHY, AUTOSOMAL DOMINANT; Myasthenic syndrome, congenital, 7, presynaptic

Summary

Presynaptic congenital myasthenic syndrome-7A with distal motor neuropathy (CMS7A) is an autosomal dominant neuromuscular disorder characterized by onset of foot deformities, delayed motor development, and slowly progressive distal muscle weakness resulting in gait difficulties in early childhood. Other features may include hyporeflexia, muscle atrophy, and upper limb involvement. Electrophysiologic studies show low compound muscle action potentials (CMAPs), consistent with a distal hereditary motor neuropathy (dHMN), as well as a decremental response to repetitive stimulation, indicating presynaptic defects at the neuromuscular junction (NMJ), consistent with myasthenic syndrome (summary by Fionda et al., 2021). The complex phenotype of patients with dominant SYT2 mutations likely results from impairment of 2 fundamental functions of SYT2: (1) disturbance of calcium-dependent synchronous presynaptic neurotransmitter release, resulting in a myasthenic disorder, and (2) disruption of exocytosis and endocytosis, causing a degenerative process affecting peripheral motor nerve terminals and resulting in a motor neuropathy (Maselli et al., 2021). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). For a discussion of genetic heterogeneity of dHMN, see 182960. [from OMIM]

Available tests

22 tests are in the database for this condition.

Clinical tests (22 available)

Molecular Genetics Tests

Genes See tests for all associated and related genes

  • Also known as: CMS7, CMS7A, CMS7B, MYSPC, SytII, SYT2
    Summary: synaptotagmin 2

Clinical features

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Imported from Human Phenotype Ontology (HPO)

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