Spinal muscular atrophy (SMA) is an autosomal recessive disease that causes progressive muscle wasting and weakness due to loss of motor neurons in the spinal cord. This is a registered cohort of spinal muscular atrophy (SMA) type I，II and III in China. This study will provide further insights into the clinical course of SMA including overall survival, demographic characteristics, motor function, respiratory support, feeding and nutritional support, growth and development. The correlation of genotype and phenotype will be conducted.