In the past, the prenatal diagnosis of this kind of disease was only through amniotic fluid or chorionic villus examination, but these methods are long-time, expensive and troublesome to operate, and are limited to some high-risk pregnant women. According to statistics, about 80% of fetal chromosomal diseases occur in ordinary pregnant women, because the absolute fertility value of this group exceeds that of high-risk groups, so prenatal diagnosis from the perspective of eugenics can not be ignored. The actual situation is that the prenatal diagnosis department of this group can't bear it so far, which eventually makes this group a blind spot for eugenics. The emergence of 1988 serum marker screening method has fundamentally changed the passive situation of prenatal prevention of the above diseases.
Down syndrome is one of the first-onset syndromes of mental retardation. In fact, the ancients had a good understanding of the clinical manifestations of Down syndrome. Archaeologists excavated a skull with typical signs of Down syndrome in the 7th century. In some sketches of16th century, you can also see some children with Down syndrome faces. 1866, a doctor named John Langdon Down first described and published the typical signs of Down syndrome, including similar facial features of such children. Therefore, this syndrome is named down syndrome after him. In 1959, the researchers confirmed that Down's syndrome was caused by chromosome abnormality (an extra chromosome 2 1). seven
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Chromosome abnormality M0jWAx
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Three types of chromosomal abnormalities lead to Down syndrome; 2 1 trisomy (about 95% of the disease), heterotopic type (about 4% of the disease) and chimeric type (about 1% of the disease). The trisomy of 2 1 is usually caused by the fact that one chromosome of 2 1 is not separated during the meiosis of the egg (see figure 1). Ectopic Down syndrome includes an extra chromosome 2 1 attached to chromosome 14, chromosome 2 1 or chromosome 22. Chimera means that the chromosomes of fertilized eggs do not separate during mitosis, so only some but not all cells have defects. 7F
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Studies have shown that there is not much difference in cognition or clinic between ectopic children and 2 1 trisomy children. Perhaps because of the mixture of trisomy cells and normal cells, the IQ of chimera children is higher than the other two types, generally between 10 ~ 30, and the incidence of clinical complications is lower than that of ectopic children and 2 10 trisomy children. Answer? & lti0
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Incident LlLp
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It may be due to the results of screening diagnosis of Down syndrome in perinatal period, and its incidence rate dropped from 1970 to1.331000, and now it is 0.92/ 1000. Many pregnant women were found to have Down syndrome virus in their fetuses in the third trimester. At present, it is believed that the incidence of Down syndrome is related to the age of pregnant women. In fact, the probability of a 20-year-old pregnant woman giving birth to a child with 2 1 trisomy is 1/2000, while the probability of a 45-year-old pregnant woman giving birth to a child with 2 1 trisomy is increased to 1/20. The age of pregnant women has little effect on the incidence of ectopic Down syndrome, but about 1/3 of these children's parents are ectopic gene carriers, and the children inherit their parents' ectopic genes. Karyotype analysis can check the risk of these parents giving birth to children with ectopic Down syndrome. Although the incidence of 2 1 trisomy is higher in men (59%) than in women, and most of ectopic children are women (74%), the mechanism is still unclear. `
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Etiology 9
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When an individual appears triploid in the "danger zone" of chromosome 2 1, he/she will show the clinical characteristics of Down syndrome. Although we don't know how the triploid in this region produces this syndrome, researchers believe that the triploid in this region, together with its adjacent related genome consisting of 50 genes, leads to this syndrome, the so-called adjacent gene syndrome. One of the genes, such as the gene encoding DYRK enzyme (bispecific tyrosine phosphokinase), plays an important role in the splicing process of ethyl bromoacetamide channel. Although the exact pathogenesis is still unclear, researchers have made great progress in embryology and neuropathology of Down syndrome since 1980s. At present, it is speculated that this deformity may be determined by triploid genes, not by variation during embryonic development. For example, although the heart may be formed according to general rules, the atrial/ventricular septum that divides the heart into two sides may not be completely closed. Similarly, there may be defects in trachea and esophagus, leading to tracheoesophageal fistula or tracheoesophageal connection. /HS@！
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Examining the brains of children with Down syndrome, we can find that there are many brain developmental abnormalities, including delayed demyelination, decreased neurons, decreased synaptic density and decreased acetylcholine neurotransmitter receptors. In addition, there is a gene encoding amyloid on chromosome 2 1, which is also found in the brain of Alzheimer's disease, which may explain why the risk of developing Alzheimer's disease in adults with Down syndrome increases with age. With the in-depth study of chromosome 2 1 gene, the mechanism of clinical manifestations other than Down syndrome will be better understood. }CF
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Early diagnosis Qw 16
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Generally speaking, pregnant women aged 35 and above should be screened for Down's syndrome in the perinatal period. In addition, many obstetricians use blood tests during the perinatal period to screen some young pregnant women for Down syndrome. If the pregnancy continues to term, early diagnosis of Down syndrome before delivery will enable clinicians to provide genetic counseling services for their families and provide appropriate medical evaluation for newborns. = & lt
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Because of its typical physical characteristics, children with Down syndrome can be diagnosed soon after delivery. 1982, Rex and Preus developed a diagnostic index based on the above eight typical physical characteristics, including palm penetration (dermatoglyphics), long ears, wide nipple spacing, wide neck webbed and wide first toe spacing. The diagnostic accuracy of the above eight typical physical characteristics for Down syndrome is 75%. However, the clinical manifestations of patients with XXXY, XXXY and XXXX syndrome in neonatal period are very similar to those of children with Down syndrome. Therefore, all newborns suspected to have Down syndrome should be analyzed for chromosome karyotype, so as to obtain correct diagnosis and provide correct genetic counseling for future pregnancy. *
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The abnormal risk rate of almost every organ/system in children with Down syndrome is higher than that in ordinary children. Knowing the basic knowledge of possible complications of such children can make medical workers evaluate and deal with more common diseases, and at the same time enhance their vigilance against other potential medical problems. & ampLNY & amp；
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Congenital heart disease A randomized study of newborns with Down syndrome found that two-thirds of these children were diagnosed with congenital heart disease by echocardiography, and the most common lesions were endocardial pad defect (leading to the communication between atrium and ventricle), atrial septal defect and ventricular septal defect. The most serious congenital heart disease is pulmonary vascular obstruction, which can lead to congestive heart failure. This potentially fatal complication develops much faster in children with Down syndrome than in children with the same heart disease but normal chromosomes. @
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Sensory dysfunction GVno\
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The incidence of hearing and visual impairment in children with Down syndrome increased significantly. A random study of 77 surviving children with Down syndrome found that more than 60% of them had eye diseases and needed treatment or monitoring. The most common diseases are ametropia, strabismus, nystagmus, blepharitis, lacrimal duct obstruction, cataract and ptosis. Among the children who have no eye diseases after general pediatric health examination, 35% actually have different degrees of eye diseases after examination by ophthalmologists. Therefore, in the first few weeks after birth, children with Down syndrome need regular eye examinations. / 1%`
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About two-thirds of children with Down syndrome have hearing loss, which may be conductive, sensorineural, or both, and may be one or both sides. Conductive deafness can be caused by structural stenosis at the back of the throat, or by repeated ear infections in susceptible children caused by autoimmune deficiency. Because tonsils and adenoids are enlarged and the upper respiratory tract is blocked, these children will have sleep apnea. k*7
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Endocrine system diseases e "
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About1141Down syndrome newborns have congenital hypothyroidism, which is about 28 times that of normal people. In addition, about 30%~50% of older children show subclinical congenital hypothyroidism. In one study, it was found that about 7% of these children eventually developed hypothyroidism. About 250 children with Down syndrome have diabetes, twice as many as the normal population. d
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From the growth pattern, the weight gain of children with Down syndrome in the first year is relatively light compared with their height, but the situation is the opposite in the following years. In early childhood, half of children are overweight. However, compared with normal children of the same age, children with Down syndrome have the same activity intensity, but consume less calories. The mechanism is that children with Down syndrome have lower resting metabolic rate, so they can gain the same weight gain with less calories. XV"}。
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In addition, because of overweight, children with Down syndrome are short and fat. The average height of adult men is 5 feet and that of adult women is 4.5 feet. Some studies show that growth hormone affects the growth and development of children with Down syndrome and accelerates their growth in a short time. However, it is not clear whether growth hormone therapy will affect the final height growth of children with Down syndrome. The safety and ethical issues of routine growth hormone therapy for children with Down syndrome need further discussion. n$R_
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Orthopedic problems +7n
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The incidence of orthopedic diseases in children with Down syndrome is also quite common, which may be related to the abnormality of ligaments. Including atlantoaxial subluxation or instability, hip dislocation, patellar instability, flat feet, but also can develop into juvenile rheumatoid arthritis. h/C
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Atlantoaxial subluxation is the most controversial and confusing problem in this kind of diseases, and the incidence rate in children with Down syndrome is about 65438 05%. But only 1% has symptoms, and this subluxation rarely leads to paralysis. The symptoms of atlantoaxial subluxation include fatigue, difficulty in walking, abnormal gait, neck pain, limited neck movement, torticollis, changes in hand function, urinary retention or incontinence, dyskinesia, sensory dysfunction, rigidity, hyperreflexia and clonus. 3rye '
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Problems 5K in Stomatology
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The most serious oral problem of children with Down syndrome is periodontal disease, which appears early and progresses rapidly, including gingivitis caused by alveolar bone loss. The clinical manifestations of this kind of diseases are mainly due to low resistance leading to gum infection. Except gingivitis, almost every child with Down syndrome has malocclusion. Many children have various dental problems, including tooth loss, dentition and tooth fusion. The eruption time of deciduous teeth or permanent teeth in children with Down syndrome is later than that in normal children 1-2 years. The average eruption time of the first deciduous teeth was 65438 03 months instead of 6 months. The incidence of dental caries in children with Down syndrome is lower than that in normal children, and its pathogenesis is still unclear. Mozi! W
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Gastrointestinal malformation p>j
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The incidence of gastrointestinal malformation in children with Down's syndrome is about 5%, which is mainly characterized by neonatal feeding difficulties, vomiting and aspiration pneumonia. Such malformations include duodenal stenosis or closure (3%), anal closure (0.9%), Hirschsprung's disease (0.5%), esophagotracheal fistula or esophageal closure (0.4%) and pyloric stenosis (0.3%). ? 1f)A
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