spinal muscular atrophy type II

spinal muscular atrophy type II

[MIM*253550] a form intermediate in severity between the infantile form (SMA type I) and the juvenile form (SMA type III); characterized by proximal muscle weakness with onset usually between 3 and 15 months of age and survival until adolescence; autosomal recessive inheritance, caused by mutation in the SMN1 gene on 5q.