Spinal muscular atrophy (SMA) refers to a type of disease that causes muscle weakness and atrophy due to degeneration of the anterior horn cells of the spinal cord. It was first reported by Werdnig (1891) and Hoffmann (1893), so it is also called Werdnig-Hoffmann disease. According to the age of onset and the degree of lesions, this disease can be divided into 4 types: Types I to III are called childhood SMA, which is an autosomal recessive genetic disease with a population incidence of 1/6000 to 1/10000. It is the most common lethal genetic disease in infancy. SMA that starts in children over 20 to 30 years old is classified as type IV, which can be inherited in different ways such as autosomal recessive, dominant and X-linked recessive, and its population incidence is about 0.32/10000. Due to various clinical and genetic characteristics, it is generally believed that this disease should be separated from motor neuron diseases and become a group of independent diseases.