Down syndrome (trisomy of chromosome 21) - a form of genomic pathology, which often contains a karyotype 47 chromosomes rather than the normal 46 as the 21st chromosome pair, instead of the normal two copies presented three
There are two forms of this syndrome: translocation of chromosome 21 to chromosome other (usually 15, sometimes 14, more rarely 21, 22 and the Y-chromosome) - 4%, and tiled embodiment syndrome - 5%.
The syndrome was named after the English physician John Down syndrome first described it in 1866. Communication between the origin of congenital syndrome and changing the number of chromosomes was found in 1959 by the French geneticist Jerome Lejeune.
The word "syndrome" refers to a set of characteristics or traits. At the use of the term preferred form of the "Down syndrome" and not "Down syndrome"
The first International Day of people with Down syndrome was held March 21, 2006. Day of the month were selected according to the number of pairs and chromosomes.
Down syndrome is a rare disease - on average there is one case per 700 births, at the moment, due to prenatal diagnosis, the incidence of children born with Down syndrome has decreased to 1 by 1100. In both sexes, the anomaly occurs with equal frequency.
The frequency of births of children with Down syndrome 1 to 800 or 1000. In 2006, the Centers for Disease Control and Prevention estimated as the one on the 733 live births in the United States (5429 new cases per year). Approximately 95% of them by trisomy of chromosome 21. Down syndrome occurs in all ethnic groups and among all economic classes.
Maternal age affects the chances of conceiving a child with Down syndrome. If a mother is from 20 to 24 years, the probability of 1 in 1562 to 30 years - 1 in 1000, from 35 to 39 years - 1 to 214, and over the age of 45, the probability of 1 to 19. Although the likelihood and increases with maternal age, 80% of children with this syndrome are born to women under the age of 35 years. This is due to a higher birth rate in this age group. According to the latest data paternal age, especially if older than 42 years, also increases the risk of the syndrome
Modern research (as of 2008) have shown that Down syndrome is due to random events during the formation of gametes and / or pregnancy. Parenting behavior and environmental factors on it does not affect.
In January 1987, there were an unusually large number of cases of Down syndrome, but the subsequent upward trend in the incidence was observed
Pregnant women can be screened for the detection of violations of the fetus. Many standard prenatal testing can detect Down syndrome in a fetus. For example, there are specific ultrasound signs of the syndrome. Genetic counseling with genetic tests (amniocentesis, chorionic villus sampling, cordocentesis) are usually offered to families in which the risk of having a child with Down syndrome is greatest. In the U.S., invasive and non-invasive survey available to all women, regardless of their age. However, invasive examination is not recommended that a woman over 34 years of age and non-invasive examination showed no apparent violations.
A child with a feature of Down syndrome (epicanthus, flat face, open mouth, enlarged tongue, small nose, etc.)
Amniocentesis and CVS are considered invasive examinations, since they in the woman's uterus introduce various tools that carries some risk of damaging the wall of the uterus, the fetus, or even miscarriage. The risk of miscarriage by chorionic villus sampling - 1%, by amniocentesis - 0.5%. Several noninvasive examinations, they are usually held at the end of the first or early in the second trimester. Each of them has a chance to get a false positive result, that is, a survey shows that fetal Down's syndrome, but in fact it is healthy. Even with the best probability of detection surveys syndrome is 90-95% and the false-positive rate of 2-5%.
At the moment, amniocentesis is considered the most accurate survey. To obtain the results of a woman is required to take the analysis of amniotic fluid in which the cells of the fetus later reveal. Laboratory work can take several weeks, but the probability of a correct result - 99.8%. False positive rate is very low.
The characteristic features commonly associated Down syndrome
Down syndrome is usually accompanied by the following external signs (according to the brochure center "DSU"):
"Flat face" - 90%
brachycephaly (abnormal shortening of the skull) - 81%
fold of skin on the neck of newborns - 81%
epicanthus (vertical fold of skin covering the medial canthus) - 80%
hypermobility of the joints - 80%
hypotonia - 80%
flat back of the head - 78%
short limbs - 70%
brahimezofalangiya (a shortening of the fingers due to hypoplasia of the middle phalanges) - 70%
cataract aged older than 8 years - 66%
open mouth (due to low muscle tone and the special structure of the sky) - 65%
dental anomalies - 65%
clinodactyly of the 5th finger (pinky curved) - 60%
arcuate sky - 58%
flat nose - 52%
furrowed tongue - 50%
transverse palmar crease (also called "monkey") - 45%
short wide neck - 45%
CHD (congenital heart defect) - 40%
short nose - 40%
strabismus (crossed eyes) - 29%
deformity of the chest, keeled or funnel - 27%
spots on the edge of the iris = Brushfilda spots - 19%
episyndrome - 8%
stenosis or atresia of the duodenum - 8%
congenital leukemia - 8%.
The degree of manifestation of mental retardation and speech development depends on innate factors and from school with your child. Children with Down syndrome are teachable. Classes with them using special methods that take into account the peculiarities of their development and perception, usually lead to good results.
Life expectancy of adults with Down syndrome has increased - by far more than the normal life expectancy of 50 years. Many people with this syndrome marry. In men, there is a limited number of sperm, the majority of men with Down syndrome are infertile. Do women have regular periods. At least 50% of women with Down syndrome to have children. 35-50% of infants born to mothers with Down syndrome are born with Down syndrome or other disabilities. 
There is evidence that people with Down syndrome are less likely to have cancer tumors .
However, people with Down syndrome are much more likely to suffer from the usual heart disease (usually a congenital heart disease), Alzheimer's disease, acute myeloid leukemia. People with Down syndrome weakened immune system, so children (especially at an early age) often suffer from pneumonia, severe in children's infections. They have frequently been observed digestive disorders, vitamin deficiency .
Cognitive development of children with Down syndrome in different cases are quite different. At the moment of birth is not possible to determine how well a child will learn and grow physically. The definition of best practices is conducted after birth with early intervention. Since children have a wide range of possibilities, their success in school by the standard curriculum can vary greatly. Learning problems that are present in children with Down syndrome can also occur in healthy, so parents can try to use a common curriculum, taught in schools.
In most cases, the children have speech problems. Between understanding speech and play it passes a certain delay. Therefore, parents are advised to drive the child to a speech therapist for training. Fine motor development is delayed and significantly behind other motor qualities. Some children may start walking as early as two years, and some only on the 4th year of birth. Typically prescribed physical therapy to speed up the process.
Often the rate of development of speech and communication skills delayed and helps to identify hearing problems. If they are present, with early intervention is a treat or prescribe hearing aids.
Children with Down syndrome in the school, usually distributed by class in a special way. This is due to learning disabilities sick children and very likely lag from their peers. The requirements in the sciences, arts, history and other subjects may be unattainable for sick children, or achieved much later than usual, for this reason, the distribution has a positive effect on learning, giving children a chance. In some European countries, such as Germany and Denmark, there is a system of "two teachers", in which the second teacher takes the children with communication problems and mental retardation, but it occurs within a class, which prevents the increase in mental gap between the children and helps the child to develop communication skills, and even their own.
As an alternative method of "two teachers" there is a program of cooperation of special and general education schools. The essence of this program is that the basic classes for weaker children are held in separate classes, so as not to distract other students, and a variety of activities, such as walking, the arts, sports, changes and interruptions to food are carried out jointly.
Known case of getting a person with Down syndrome university education.
Based on materials from wikipedia