Childhood autism is a subtype of pervasive developmental disorder. It is a developmental disorder that occurs in early childhood and is characterized by obstacles to contact with the outside world (including parents). It is mainly manifested by varying degrees of interpersonal communication disorders, narrow interests and stereotyped behavior. About 3/4 of children have obvious mental retardation, and some children have better abilities in certain aspects against the background of general intellectual retardation. It is more common in boys. In the past, it was called infantile autism and childhood autism. It is related to children's psychological activities in multiple fields such as perception, language and thinking, emotion, movement and social interaction, and is a developmental disorder. In taxonomy, it is currently classified as a psychological development disorder, called pervasive developmental disorder. The cause of this disease is unknown. Twin studies have shown that the prevalence of the disease in monozygotic twins is higher than that in dizygotic twins. Both electroencephalogram and brain imaging examinations have a high abnormality rate, but are not specific. There are also many soft signs of the nervous system. Some diseases, such as fragile X chromosome syndrome, are also more common in patients with autistic symptoms.