Proximal spinal muscular atrophy: current orthopedic perspective

Figures & data

Table 1 Classification of proximal SMA

SMA type	Age of onset	Achieved function	Life expectancy
Ia (more severe)	Prenatal to 6 months	No sitting or turning	<2.5 years
Ib (less severe)	Prenatal to 6 months	No sitting or turning	2.5–20 years*
II (intermediate)	Birth to 18 months	Sitting ability	2.5–30 years*
IIIa (mild; retarded motor development)	Birth to 3 years	Walking ability	Fourth to fifth decade; normal
IIIb (mild; normal motor development)	>3–30 years	Walking ability	Fourth to sixth decade; normal
IV (adult)	>30 years	Walking ability	Normal

Note:

* Possible longer life expectancy.

Abbreviation: SMA, spinal muscular atrophy.