Down syndrome, first called Mongolism or Mongolianidiocy, is now generally known as trisomy 21, also known as congenital stupidity in China, and is one of the most common serious birth defect disorders. Down’s syndrome was diagnosed in 1866 by the British doctor Don? John? JohnLangdonDown was first published by the Society in 1866. In 1965, the WHO officially named the disorder “Down syndrome”. It encompasses a range of genetic disorders, the most representative of which is trisomy 21, which causes high levels of abnormalities including learning disabilities, intellectual disabilities and handicaps. The prevalence of Down syndrome is not directly related to ethnicity, standard of living, etc. It is estimated that one in every 660 births has Down syndrome, making it the most common chromosomal variant. Advanced maternal age increases the risk of Down syndrome in infants. Families at potentially high risk are often offered genetic counseling and genetic testing such as “amniotic fluid diagnosis”. There are basically three types of Down syndrome: 1. Trisomy of the 21st chromosome pair. Trisomy 21: also known as Trisomy 21, the 21st chromosome pair has one extra chromosome and there are 47 chromosomes in the cell, accounting for 90-95% of people with Down syndrome. 2.Translocation of chromosomes: 5-6% of all cases. The extra chromosome is attached to other chromosomes, especially the fourteenth or twenty-first pair of chromosomes. 5-6% of people with Down syndrome are in this category. 3. Mosaicism: 1-3% of the total population. Not all cells have 47 chromosomes, some have 47 chromosomes and some have 46 chromosomes. Common complications of Down’s syndrome: People with Down’s syndrome have a higher chance of having organ malformations, but not all complications occur, and there are cases where there are no complications at all. 1. digestive organ malformations, such as congenital esophageal atresia, duodenal stenosis, lockjaw, etc. 2. congenital heart disease, with a prevalence of up to 40%, especially endocardial insufficiency, which is usually fatal if not treated early. 3. cataracts, with a prevalence of 2%. 4. Acute leukemia, with a prevalence of 1%. 5. Indirect instability of the annulus, prevalence of 2-3%. 6. Thyroid disease with a prevalence of 3%. 7. Nodding epilepsy with a prevalence of 10%. 8. Transient myelodysplasia. 9. Eye anomalies, myopia, hyperopia, disorderly vision, etc. caused by corneal and crystal body anomalies. 10, leaching otitis media, easy to accumulate liquid in the inner ear triggering otitis, affecting hearing Seven characteristics of Down syndrome (1) mental retardation: mild, moderate, mostly moderate mental retardation, its intelligence gradually decreases with age, the age grows from 1 to 10 years old, and its average intelligence quotient (IQ) decreases from 58 to below 40. Some experts believe that IQ is relatively stable during adolescence and decreases later. Most studies have shown that environmental factors are important in influencing IQ, and that patients raised in good environments have relatively high IQs. The degree of mental retardation can vary between different types of patients, with trisomies generally being the most severe and translocations the next most severe. Among the translocation types, those with balanced translocation have a lesser degree of intellectual involvement. As the children are quiet and docile, they provide better conditions for special education training. Although it is difficult to reach the level of elementary school grade 1-2 in terms of cultural skills, there can be significant improvement in adaptive ability and a certain degree of self-care and labor ability. (2) Language development disorders: The average age of children starting to learn to speak is 4-6 years old, 95% of them have articulation defects, slurred speech, stuttering, low voice; more than 1/3 of them have abnormal speech rhythm or even outburst sounds. (3) Behavioral disorders: most of them are mild-mannered, often giggle, like to imitate and repeat some simple actions, and can perform simple labor. A few patients are irritable, capricious, hyperactive, and even have destructive and aggressive behaviors, and some show a tendency to flinch, accompanied by posture of catatonia. (4) Delayed motor development: The difference between the motor function of the child and that of a normal child of the same age may not be significant during the period after birth, but increases with age. Motor development also varies widely among patients. Patients with congenital dwarfism can perform simple movements such as dressing and eating, but their movements are clumsy, uncoordinated, and their gait is unstable. (5) Growth disorders: Maternal gestation period is shorter in patients with congenital dwarfism, with an average of 262 to 272 days. At birth, the height is l~3 cm shorter than normal newborns, the head circumference is basically normal, the biparietal diameter is within the normal range, the anterior-posterior diameter is relatively short, and the occipital area is flat. Most of them have a short head shape. The fontanelle and forehead sutures are wide and close late, and the third fontanelle (the sagittal suture above the posterior fontanelle is widened) often appears. Most children with this disease sleep deeply for a few days after birth, sucking and swallowing are very slow, or even completely unable, so it is very difficult to wake up and feed. 80% of children with this disease have generally low muscle tone. (6) Special appearance: wide eye spacing, upward slanting of the outer corners of the eyes, inner canthus, low ear position, low nasal bridge, wide and thick tongue, mouth often half open or tongue sticking out of the mouth, deep and many furrows on the tongue, thick palms and short thick fingers, short last fingers often bent inward or with two knuckles, 40% of children with through palm. In the metatarsal pattern, the tibial arch of the ball area of the thumb, the distance between the thumb and the second toe is large, and the joint ligaments are lax or see low muscle tone.