Clinical classification of spinal muscular atrophy (SMA)

Type	Age of onset	Requires respiratory support at birth	Able to sit	Able to stand	Able to walk	Life expectancy	Predicted SMN2 copy number
0	Prenatal	Yes	No	No	No	<6 months	1
1	<6 months	No	No	No	No	<2 years	2
2	6 to 18 months	No	Yes	No	No	10 to 40 years	3
3	>18 months	No	Yes	Yes	Assisted	Adult	3 to 4
4	>5 years	No	Yes	Yes	Yes	Adult	>4

From: Butchbach ME. Copy Number Variations in the Survival Motor Neuron Genes: Implications for Spinal Muscular Atrophy and Other Neurodegenerative Diseases. Front Mol Biosci 2016; 3:7. Copyright © 2016 Butchbach. Available at: http://journal.frontiersin.org/article/10.3389/fmolb.2016.00007/full (Accessed on March 27, 2017). Reproduced under the terms of the Creative Commons Attribution License.

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