Werdnig-Hoffman disease
severe infantile spinal muscular atrophy
spinal muscular atrophy type I

Approximately 80 percent of individuals with SMA fall into the severe category (Werdnig-Hoffman disease or SMA1).

Werdnig-Hoffman disease, which is also known as spinal muscular atrophy type 1 (SMA1) or acute spinal muscular atrophy, refers to individuals who have symptom onset prior to 6 months of age.