Table 1.

Classification and prognosis of different types of autosomal recessive proximal spinal muscular atrophy[1,2]

Types		Manifestation	Functional grading	Life expectancy
Ia	more severe	prenatal (30%) to 3-6 months	unable to roll over or sit	< 30 months = 100%
				< 18 months = 95%
				< 7 months = 50%
Ib	less severe	like Ia	like Ia	2.5 - 20 years *
II	intermediate	birth -18 months	sitting	2.5 - 30 years *
IIIa	mild, retarded motor development	to 3 years	walking	4th – 6th decade, usually normal
IIIb	mild, normal motor development	> 3 - 30 years	walking
IV	adult	> 30 years	walking	normal

* Longer life expectancy is quite possible.