"This disorder affects 1 in 6000-10000 infants 1."
"Some authors suggest an additional type 0, also termed 'severe infantile' form, with a prognosis (without novel therapy) of just a few weeks, although this has not been widely adopted in the literature 4."
"Spinal muscular atrophy has an autosomal recessive mode of inheritance due to mutations to the SMN1 (survival motor neurone 1) gene on chromosome 5 1,2. This mutated gene has a carrier frequency of 1 in 40 1,2. In addition to SMN1, SMN2, the homologous copy of SMN1, also plays a role in modulating the severity of the phenotype 11. Having a higher number of SMN2 copies (up to five) correlates with having a milder phenotype 11."
"In infants, the most common demographic affected, this weakness classically manifests as difficulties sitting and rolling, assuming a frog-leg position, a weak cry, and increased respiratory effort with paradoxical breathing 1,3. Rarely is intellectual disability an associated feature 3."