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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