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Table 1 Clinical classification of spinal muscular atrophy

From: Prevalence, incidence and carrier frequency of 5q–linked spinal muscular atrophy – a literature review

SMA type

OMIM number

Age of onset

Highest achieved motor function

Natural age of death

0

-

Prenatal/ Foetal

Nil

<6 months

I

253300

<6 months

Sit with support only

<2 years

II

253550

6–18 months

Sit independently

>2 years

III

253400

>18 months

Stand and walk

Adulthood

IV

271150

Adult (2nd or 3rd decade)

Walk during adulthood

Adult

  1. OMIM Online Mendelian Inheritance in Man