Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness and atrophy caused by the degeneration of motor neurons in the anterior horn of the spinal cord. The disease is the number one fatal genetic disease in infancy, and it is estimated that there is one case in every 10,000 live births; the carrier rate of the general population is about 1/50, and the carrier rate of the domestic population is about 1/42.