Down's Syndrome - chromosomal diseasedue to violation of autosomes (chromosomes pun intended). The disease is not hereditary, genetic disorders occur when the reproductive process. The probability of the birth of sick children increased c age parents. Currently, it is possible to detect abnormalities in early pregnancy.
Down Syndrome (trisomiya on chromosome 21) isa form of genomic human pathology in which there are 47 in the genotype of the chromosomes during normal - 46. Instead of two chromosomes 21 minutes, there are three pairs of chromosomes (trisomiya).
Causes of Down Syndrome
The mechanism of genetic disease
The pathology begins to develop in the embryonicperiod. Connected extra chromosome impairs REST gene which then provokes a number of changes in other genes that regulate development of the organism at the level of embryonic stem cells.
Simple full trisomiya (non-hereditaryversion) is observed in 95% of patients, it is due to neraskhozhdeniem chromosomes during meiosis. The 1% is observed mosaicism - the extra chromosome contains not all cells of the body. In other cases, the syndrome may be caused by an inherited translokatsiey chromosome 21, occurring as a result of the merger tsentromery chromosome 21 and another chromosome akrotsentricheskoy.
C Children Down Syndrome
The probability of a sick child birth
Down syndrome occurs in one out of 700delivery. This ratio does not depend on the countries, climates, races, and social classes. No effect is also a way of life of parents. Extra chromosome is a random result in the formation of sex cells - eggs or sperm - either during the first division of the new body's cells after fertilization. The ratio of girls to boys among newborns with abnormal ratio is 1: 1.
If the sick one of identical twins, thepatients inevitably another. In raznoyaytsevyh twins no such relationship exists. This fact once again confirms the chromosomal origin of the disease. However, Down's syndrome, hereditary disease is not, the defective gene is passed down from generation to generation is not - Disorder occurs when the reproductive process.
Factors that create the risk of Down's syndrome
The probability of the birth of sick children depends onthe age of the child's father and mother and the degree of consanguinity of the spouses. The biggest impact has the age of the mother. For women up to 25 years the probability of having a child with a pathology is 1/1400, from 25 to 30 years - 1/1000, from 30 to 35 - 1/350. The risk increases goda 42 to 1/60, and the probability in 49 years is already 1/12. According to some studies the probability of a sick child birth also depends on the age of maternal grandmother. The older she was at the time of the birth of his daughter, the more likely the birth of sick grandchildren.
Down's Syndrome Treatment
At present there are no effective drugs for the treatment of Down's syndrome. Under development are preparations based on hormones of the pituitary and thyroid gland.
Pregnant women over the age of 35 yearsamniotsenteza advised to undergo the procedure - the analysis of the chromosomal composition of the cells contained in the amniotic fluid. This method makes it possible to get the exact results of the genotype of the child and in case of detection of pathology - to terminate the pregnancy. Currently, thanks to prenatalnoy diagnosis could almost halve the rate of birth of sick children - 1/1100.
Symptoms of Down Syndrome
Reflection of genetic disease on the patient's appearance
For people with Down's syndrome is characterized by a number of external signs:
- "Flat face" - about 90%;
- beveled shape of the eyes - 80%;
- shortened skull (brachycephaly) - 81%;
- flat neck - 78%;
- shortened nose - 40%;
- flat bridge of the nose - 52%;
- short and wide neck, poorly developed adherent earlobes - 45%;
- hypotonia and giperpodvizhnye joints - 80%;
- strabismus - 29%;
- Brushfilda spots (dark spots on the edge of the iris) - 19%;
- arcuate palate - 58%;
- dental anomalies - 65%;
- grooved tongue - 50%;
- short legs - 70%;
- brahimezofalangiya (shortened fingers) - 70%;
- twisted little finger - 60%;
- transverse palmar crease - 45%;
- kilevidnaya or funnel chest deformity - 27%.
Due to the special structure of the palate and low tonemuscles in 65% of patients are constantly open mouth. Characteristic features are hoarse voice, short stature, and mental retardation. IQ Down Syndrome lies in the range of 30-50.
In 66% of children over the age of 8 years developingcataracts may occur congenital heart disease (40%), gastrointestinal abnormalities (15%), epicindrom (8%) and congenital leukemia (8%). Patients with Down syndrome are more resistant to cancer. By assumption, scholars, chromosome 21 has the ability to prevent the uncontrolled cell growth, and a third copy of the gene enhances this ability.