Autism, also known as autism or autisticdisorder, etc., is a representative disorder of pervasive development. The DSM-IV-TR classifies PDDs into 5 categories: autistic disorder, Retts syndrome, childhood disintegrative disorder, Asperger syndrome, and unspecified PDD. among them, autistic disorder and Asperger syndrome are more common. The prevalence of autism has been reported inconsistently and is generally considered to be about 2 to 5 per 10,000 of the child population, with a male to female ratio of about 3:1 to 4:1, with girls generally having more severe symptoms than boys. Although the etiology of autism is not fully understood, current research suggests that certain risk factors may be associated with the development of autism. The risk factors for autism can be grouped into genetic, infectious and immune, and physical and chemical stimuli during pregnancy. Genetic factors Dizygotic studies have shown that the co-prevalence of autism is as high as 61-90% in monozygotic twins, while no significant co-prevalence is seen in dizygotic twins. The re-prevalence between siblings is estimated to be around 4 or 5%. These phenomena suggest a genetic predisposition to autism. Studies have shown that certain chromosomal abnormalities may contribute to the development of autism. The chromosomes known to be relevant are 7q, 22q13, 2q37, 18q, and Xp; certain sex chromosome abnormalities can also present with autism. Examples include 47, XYY, and 45, X/46, and XY chimerism. Four of the more common chromosomal disorders that show symptoms of autism are fragile X chromosome syndrome, tuberous sclerosis, 15q diploidy, and phenylketonuria. New candidate genes for autism are reported every year. New autism candidate genes reported in recent years include CLOCK, PRKCBl, CNTN4, CNTCAP2, immunegene, STK39, MAOA, CSMD3, DRD1, neurexinl, SLC25A12, JARDlC, Pax6. Another study reported that in Han Chinese autism patients, the NRP2 gene presence of genetic polymorphisms. The large number of candidate genes suggests that autism is a polygenic genetic disorder, i.e., autism may be a disorder induced by environmental pathogenic factors under a certain genetic predisposition. Infectious and immune factors As early as the late 1970s, studies found that pregnant women with viral infections had an increased chance of developing autism in their offspring. Several subsequent studies have suggested that there may be a relationship between infection during pregnancy and the development of autism. Currently known associated pathogens include: rubella virus, cytomegalovirus, varicella-zoster virus, herpes simplex virus, syphilis spirochetes, and toxoplasma. It is currently speculated that antibodies produced by these pathogens, which enter the fetus by the placenta, cross-immune with the developing fetal nervous system and interfere with the normal development of the nervous system, thus leading to autism. Stimulation by physical and chemical factors during pregnancy A history of medication with reaction stops and valproate-based antiepileptic drugs and alcohol abuse in early pregnancy can lead to an increased chance of autism in the offspring. According to these studies, the offspring of rats given a single high dose of sodium valproate intraperitoneally at 12 and 5 d of pregnancy exhibited autism-like behavioral manifestations. It has also been found that exposure of pregnant rats to repeated freezing stimuli also increases the chance of autism in the offspring; the offspring of pregnant rats subjected to repeated freezing stimuli also exhibit behavioral features of autism. Clinical manifestations The disorder generally begins at 36 months of age or younger and is characterized by three core categories of symptoms: social interaction disorders, communication disorders, narrow interests, and stereotypical repetitive behaviors. Children with this disorder have qualitative deficits in social interactions. In infancy, the child avoids eye contact, lacks interest and responsiveness to human voices, does not expect to be picked up, or is stiff and unwilling to be held close to others. In early childhood, the child still avoids eye contact, often does not respond to calls, does not develop attachment to parents, lacks interest in interacting or playing with peers, does not interact with peers in an appropriate manner, does not form partnerships with peers, does not share happiness with others, and does not seek comfort from others when upset or hurt. After school age, as they grow older and their condition improves, affected children may become friendly and affectionate with their parents and peers, but still clearly lack the interest and behavior to actively interact with others. Although some children are willing to interact with others, there are still problems with the way they interact. They lack understanding of social constants, lack responsiveness to the emotions of others, and are unable to adapt their behavior to social situations. In adulthood, the children still lack the interest in interaction and social skills to establish romantic relationships and get married. Children with this disorder often cry or scream to express their discomfort or needs. Older children may pull an adult’s hand toward something they want. They lack facial expressions and often appear indifferent, rarely nodding, shaking their heads, or waving their hands to express their wishes. (2) Speech communication disorders are obvious in children with this disorder, including: ① Language comprehension is impaired to varying degrees; ② Speech development is delayed or non-developed, and some children have expressive speech before the age of 2-3, but it gradually decreases or even disappears completely; ③ Abnormalities in the form and content of speech: children often have imitation speech, stereotypical repetition of speech, grammatical structure, personal pronouns are often wrong, and intonation, speed of speech, syllables, and so on. ④ Impaired verbal ability: Although some children can recite children’s songs and advertisements, they seldom communicate verbally, and they do not propose topics, maintain topics, or talk only with stereotypical repetitive phrases and dwell on the same topic. The child is particularly interested in objects that are not usually toys, such as wheels, bottle caps, and other round, rotatable objects. Some children also develop attachment behaviors to inanimate objects such as plastic bottles and wooden sticks. The child’s behaviors are often stereotypical, such as doing things or playing with toys in the same way, requiring objects to be placed in a fixed location, walking the same route when going out, and eating only a few foods for a long period of time. There are often repetitive movements and strange and bizarre behaviors, such as jumping repeatedly, staring at the hands in front of the eyes, fluttering or walking on the tips of the feet. Other symptoms About 3/4 of children with this disorder have mental retardation. About 1/3-1/4 of the children have a combination of epilepsy. Some children with mental retardation may also have “autistic aptitude”, such as musical, calculation, date calculation, mechanical memory and recitation, and are called “idiot scholars”.