spinal muscular atrophy type I
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spinal mus·cu·lar at·ro·phy type I[MIM*253300]
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 half of affected 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.