2 1 trisomy syndrome, also known as congenital idiocy, or DSDown Syndrome, is an autosomal aberration, which is the most common type of chromosomal diseases in children. The incidence rate in live infants is about1/(600 ~ 800), and the older the mother, the higher the incidence rate of this disease. 60% of the children died early in the fetus. 2 1 trisomy syndrome contains a series of genetic diseases, among which the most representative trisomy phenomenon of chromosome 2 1 will lead to high deformities including learning disabilities, mental retardation and disability. 2 1 trisomy syndrome is a disease caused by chromosome structural aberration. The patient's karyotype is 47,XX(XY),+2 1. The reason is that the chromosome 2 1 does not separate during meiosis, resulting in abnormal eggs.

clinical picture

The main characteristics of children with 21-trisomy syndrome are mental retardation, physical retardation and special face. The child's eye distance is wide, the nose bridge is flat, the eye fissure is small, the lateral side of the eye is inclined, there is epicanthus, the external ear is small, the hard palate is narrow, the tongue often sticks out of the mouth, and there are many salivation; Short stature, head circumference less than normal, bone age often lags behind age, delayed teething and often dislocation; Hair is soft and less; The limbs are short, because the ligaments are slack, the joints can be excessively bent, the fingers are thick and short, and the little finger bends inward. Downer syndrome

The skin texture features are: penetrating the hand and increasing the atd angle; The fourth and fifth fingers increased in radial dustpan; There is only one finger fold on the tibia of the foot, thumb and fifth finger. Children have obvious special faces at birth, and often show drowsiness and feeding difficulties. With the increase of age, its mental retardation is gradually obvious, and its motor development and sexual development are delayed. About 30% of children are accompanied by congenital heart disease and other malformations. Because of low immune function, it is easy to suffer from various infections, and the incidence of leukemia is also increased by10 ~ 30 times. If you survive to adulthood, you will often have symptoms of senile dementia after the age of 30.