Down syndrome

Down syndrome call rather widespread genetic disease of which first of all lag in intellectual and physical development is characteristic. In 1866 the British doctor John Lengdon Down for the first time described signs of the patients subject to this pathology. On its surname the syndrome is called. However origins of this genetic anomaly were established only in the middle of the twentieth century by the French geneticist Le Jeune.

Down syndrome reasons

Such pathology as Down syndrome, is connected with disturbance in a set of chromosomes and is characterized as existence of an additional 47th chromosome in a karyotype whereas norm is figure 46. It is shown in disturbances of intellectual and physical development of the person. It is necessary to tell that one child from 600-700 newborn children is subject to this disease, irrespective of an ethnic origin. This anomaly meets identical frequency among representatives of both floors.

As it was already noted, the reasons of a Down syndrome were established relatively recently though opinions of specialists in the field on this matter disperse still. Let's consider major factors which influence probability of developing of pathology at children:

• Age of parents;
• Closely related marriages;
• Age of the grandmother of the child on the maternal line.

As the first reason of a Down syndrome, on medical observations, the age of mother of the child acts. So, it is known that the probability of conception of the child with this pathology at age of the woman from 25 to 30 years makes 1 to 1000, from 35 to 40 - 1 to 200, and after 45 years – 1 to 20. Meanwhile specialists cannot explain completely interrelation between a syndrome and age of mother. Some of them believe that it is caused by disturbances which arise at the second division of meiosis happening already at the adult woman. It is also established that the age of the father of the child plays an important role, especially if to it for 42.

Closely related marriages are the least common cause of a Down syndrome in the civilized world. However as the most interesting factor from the scientific point of view the interrelation between a disease and age of the grandmother in the area of the child's mother acts. Researches showed that than the grandmother when gave birth to the daughter was more senior, that a high probability that at her daughter the kid with this pathology will be born.

This fact speaks as follows. Still the female embryo undergoes process of the first division of meiosis during which there is a discrepancy of chromosomes in mother's womb. Substances which come from mother to a fruit to this period are capable to make impact also on development of its sex cells. Female children are born with a ready set of future ova which already underwent the first division of meiosis. Among this set a certain part of ova has an excess chromosome and if one of them is impregnated afterwards, then the child will be born with a Down syndrome. Thus, it is considered that the quantity of similar cells in ovaries at the newborn directly depends on age of her mother.

Symptoms of a Down syndrome

Today the woman during pregnancy can undergo some inspections on definition of existence at a fruit of this genetic anomaly. It is known that they are the reason of decrease in number of sick children recently as many women in situation, having revealed disturbances, interrupt pregnancy.

If the child was already born, then a number of characteristic external symptoms of a Down syndrome can demonstrate existence of a disease:

• Plane of the person and nape;
• The shortened skull;
• Short hands and legs;
• Short fingers;
• The skin fold covering an eye corner;
• Skin fold on a neck.

These are the most widespread symptoms of a Down syndrome which are observed in 70-90% of cases. Together with it there are also others which meet less often, but also are characteristic of this disease. Among them it should be noted such:

• Plane of a nose bridge and nose;
• Wide and short neck;
• Little finger curvature;
• Development of a cataract after eight-year age;
• Anomalies of teeth;
• Open mouth;
• Arc-shaped sky.

Besides, in development of a Down syndrome it is possible to note such pathologies as a hypomyotonia, deformation of a thorax, squint, inborn heart disease and a leukosis.

Diagnosis of a Down syndrome

To find development of a Down syndrome, there are some main diagnostic methods. The first of them is the ultrasonography research. In the first trimester of pregnancy the woman can pass a test for measurement of collar space of a fruit. If according to test results, carried out by means of the vulval sensor, its thickness exceeds 2,5 mm, then it is possible to speak about existence of a disease at future child. If the research was conducted through a front wall of a stomach, then at a fruit tells an indicator from 3 mm about presence of pathology. Besides, it is possible to carry out ultrasonography on existence of a nasal bone: at development of a Down syndrome it at a fruit or very small, or in general is absent.

As the second widespread diagnostic method in this case double biochemical analysis of blood on the 10-13th week of pregnancy and triple – on the 16-18th week acts. After results of ultrasonography and analyses are received, for reliable diagnosis of a Down syndrome it is possible to pass a horionbiopsiya or amniocentesis most of which precisely distinguish existence of genetic anomalies of a fruit. Horionbiopsiya assumes the analysis of fabrics of a cover of an embryo, and amniocentesis represents a puncture of a front wall of a stomach of mother for the purpose of capture for the analysis of fabrics of a fruit or amniotic waters.

It should be noted that these procedures bear in themselves big danger, as for health of future mother, and the child. During inspection internal injuries of the woman, bleeding, a fruit injury, and also threat of abortion are possible.

It is important to add that the Down syndrome was considered as an incurable disease until recently. However quite recently in the USA the experiment which gives consolatory forecasts was made. During the research the possibility of blocking of the excess chromosome in a karyotype influencing development of pathology was found.