spinal muscular atrophy, type I


Also found in: Acronyms.

spi·nal mus·cu·lar at·ro·phy, type I

(spī'năl mŭs'kyū-lăr at'rŏ-fē tīp)
The early infantile form, characterized by profound muscle weakness and wasting with onset at or shortly after birth; death occurs usually before 2 years of age. Autosomal recessive inheritance, caused by mutation in the survival motor neuron gene (SMN1) on 5q. About one half of patients are also missing both homologues of a neighboring gene that encodes neuronal apoptosis inhibitory protein (NAIP), the loss of which is thought to influence the severity of the disease.
Synonym(s): Hoffmann muscular atrophy.
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