Spinal Muscular Atrophies of Childhood definition

Spinal Muscular Atrophies of Childhood
HMN (Hereditary Motor Neuropathy) Proximal Type I; Muscular Atrophy, Spinal, Type I; Muscular Atrophy, Spinal, Type II; Muscular Atrophy, Spinal, Type III; Proximal Hereditary Motor Neuropathy Type I; Spinal Muscular Atrophy Type I
A group of recessively inherited diseases that feature progressive muscular atrophy and hypotonia. They are classified as type I (Werdnig-Hoffman disease), type II (intermediate form), and type III (Kugelberg-Welander disease). Type I is fatal in infancy, type II has a late infantile onset and is associated with survival into the second or third decade. Type III has its onset in childhood, and is slowly progressive. (J Med Genet 1996 Apr:33(4):281-3)