Synonyms
SMA type Werdnig-Hoffmann (type I); Intermediate SMA (type II); SMA type Kugelberg-Welander (type III); SMA
Definition and Characteristics
Degeneration and loss of the anterior horn cells in the spinal cord, and – depending on type and severity – sometimes also of the brainstem nuclei, resulting in muscle weakness and atrophy. The sensory neurons are clinically spared, and there are no signs of upper motor neuron (pyramidal tract) involvement. Types defined according to achieved motor milestones: I: ability to sit not achieved; II: ability to sit but not to walk; III: ability to walk [1].
Prevalence
Considering the incidence of at least 1:10.000 for acute and chronic autosomal recessive proximal SMA, the estimated heterozygosity frequency is about 1:50 in the general population. Autosomal dominantly inherited SMA is extremely rare in infancy and youth.
Genes
Homozygous deletions of the SMN1 gene (5q11.2–q13.3) [2] are detected in more than 90% of SMA type I–III patients....
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References
Zerres K, Rudnik-Schöneborn S (1995) Natural history in proximal spinal muscular atrophy (SMA): clinical analysis of 445 patients and suggestions for a modification of existing classifications. Arch Neurol 52:518–523
Lefebvre S, Bürglen L, Reboullet S et al. (1995) Identification and characterization of a spinal muscular atrophy-determining gene. Cell 80:155–165
Monani UR (2005) Spinal muscular atrophy: a deficiency in a ubiquitous protein; a motor neuron-specific disease. Neuron 48:885–896
Wang CH, Finkel RS, Bertini ES et al. (2007) Consensus statement for standard of care in spinal muscular atrophy. J Child Neurol 22:1027–1049
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Zerres, K., Rudnik-Schöneborn, S. (2009). Muscular Atrophy, Spinal I–III. In: Lang, F. (eds) Encyclopedia of Molecular Mechanisms of Disease. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-29676-8_1651
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DOI: https://doi.org/10.1007/978-3-540-29676-8_1651
Publisher Name: Springer, Berlin, Heidelberg
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