A palmar atd angle greater than 45deg; is a specific appearance of mental retardation congenital dysgenesis (21 III sign, Down syndrome) due to chromosomal abnormalities. This symptom is present in approximately 40% of patients. Mental retardation (mentalretardation) is a syndrome in which an individual’s intellectual functioning is significantly lower than that of his or her peers due to mental retardation, impaired or hindered intellectual development, accompanied by difficulties in social adjustment as the main feature before maturity (usually before the age of 18). The causes of mental retardation are both genetic and environmental, and once it occurs, it is difficult to reverse, so prevention should be emphasized. Monitoring of genetic disorders, perinatal care, prevention and early treatment of central nervous system disorders are important preventive measures. Some developed countries have implemented blood biochemical screening for several genetic metabolic disorders in all newborns based on specific legislation, providing for early prevention and treatment. Pre-symptomatic diagnosis and prevention of functional disability: (1) Regular examination of infants and children using knowledge and techniques of child developmental psychology, regular visits and early intervention for suspected children. (2) Provide intensive education and training for children with mental retardation whose main cause is sociocultural or psychosocial factors. (3) Actively prevent and treat emotional and behavioral disorders in children with various types of mental retardation. Parents and teachers should be educated about mental retardation disorders so that they are familiar with what kind of psychological and neurological disorders may occur in the affected children at different periods of time and the general methods of disposal. Reduce disability and improve compensation. This mainly includes behavioral and life counseling, special education and training, and counseling services to help overcome the difficulties exhibited by patients in behavioral and personality problems, and symptomatic treatment of those with combined physical dysfunction or other deformities, in order to restore the optimal level of function and provide conditions for future participation in social life and employment. In education and training, attention should be paid to structured and individualized teaching, with the main goal of improving self-care ability and survival ability, and conscious education on the rights and interests of the disabled and the legal system, so that they know the possible ways and means to protect their legitimate rights and interests.