What causes Down syndrome?

Many modern people are aware of Down syndrome, especially pregnant women, who must take active measures to prevent the birth of children with Down syndrome. Today's prenatal doctors usually recommend pregnant women to take a Down syndrome test. If the test shows that the child is at high risk, further testing is necessary to prevent the birth of a Down syndrome child. So what causes Down syndrome? What are the characteristics of Down syndrome?

1. What causes Down syndrome?

Down syndrome is a sex chromosome defect disease, also known as "congenital idiocy", and is one of the first syndromes combined with mental retardation. Down syndrome is caused by a genetic mutation. The patient's 21st chromosome changes from the normal 2 to 3, so it is also called "Trisomy 21 syndrome". It is one of the most common birth defects in my country.

It is mainly caused by the failure of one of the alleles in the somatic cells to produce gametes during meiosis, or the fusion of sperm and egg during mitosis, resulting in the failure of sex chromosome 21 to separate. Because most of the single-type patients cannot survive, they usually only give birth to triple-type offspring. There is an extra sex chromosome 21 in the embryonic cells. The pathogenesis is mostly related to the fragility of the eggs caused by the advanced age of the pregnant woman; 5% are caused by the father. Only a few cases are familial genetic inheritance, in which the secondary coils produced by somatic cells during meiosis do not separate. Because male patients with Down syndrome cannot get pregnant, there will be no problem of genetic inheritance in offspring. Therefore, women who want to get pregnant should do so as soon as possible. The older a woman is when she becomes pregnant, the greater the risk of having a baby with Down syndrome.

2. What are the symptoms of Down syndrome?

Down syndrome, also known as congenital idiocy, is a sex chromosome defect disease. Its key features are as follows:

1. The patient has significant unique clinical symptoms

Such as wide distance between eyes, low bridge of nose, small palpebral fissure, upward slanting eyes, excess skin at the corners of eyes, small external auditory canal, fat tongue that often sticks out of the mouth, and excessive drooling. The baby is short, with a head circumference lower than normal, short front and back diameters, and a flat back of the head. The neck is short and the skin is relatively loose. Bone age measurement often lags behind chronological age, and tooth eruption is delayed and often shifted. The hair is soft and less. If the anterior fontanelle closes late, a third fontanelle may appear on the center line of the parietal occipital. The limbs are short. Due to the loose ligaments, the joints can bend too much. The fingers are short and thick. The middle part of the little finger is underdeveloped, causing the little finger to bend inward. The phalanges are short. The trident of the palm moves distally. The palm lines and numb feet are common. More than half of the patients have arched skin lines on the ball of the big toe.