Down syndrome: causes, symptoms, diagnosis, treatment
Down Syndrome is a genetic disorder in which the karyotype consists of 47 chromosomes instead of the usual 46.
When the germ cells are formed during meiosis, the pair chromosomes must diverge, but if for some reason this does not happen, a third 21-chromosome( trisomy).
An abnormality occurs in approximately one in 800 newborns and in 88% of cases this occurs because of the non-separation of female gametes.
Why develops Down's Syndrome, and what is it? The main risk factor that increases the likelihood of a child with Down's syndrome is the age of the expectant mother. At 45, the risk of having a sick child is 1:30.
Although, according to statistics, children with this anomaly are born more often in young women, which is explained by the large number of births. The age of the father does not affect the appearance of pathology. This is due to the fact that male sex cells are updated every 72 days and do not accumulate toxic substances.
In women, the ovaries are kept in the ovaries from the moment of birth, which means that contacts with harmful chemicals, radiation, and the abuse of alcohol and smoking can negatively affect them.
If the family already has one "solar" child, then there is a low probability of birth( on average 1%) and a second baby with Down syndrome. Also, the risk of trisomy in the offspring may increase the kinship of the parents.
Down syndrome occurs as a result of abnormal cell division, when unnecessary genetic matter is glued to the 21st pair of chromosomes.
Pathology can have three versions: trisomy, mosaicism, translocation. The most common is trisomy, caused by non-dissociation of chromosomes during the period of cell division. Three chromosomes instead of two are observed in all cells of the child. The exact cause of this phenomenon is unknown until now.
Mosaicism is a more rare and mild form of the syndrome and differs in that not all cells have an additional chromosome, only some tissues and organs are affected. Nondisjunction arises not in the formation of the reproductive cells of parents, as in the first case, but in the early stages of embryo development.
With translocation during cell fusion, a part of one chromosome in the 21st pair is displaced to the side of another chromosome.
Usually Down syndrome is defined by a number of external symptoms that are not difficult to detect in humans:
Pathology is usually detected before the birth of a child. Future mothers are offered to undergo a comprehensive test, which is conducted between the 11th and 13th week of pregnancy, and between the 15th and 20th week in the second trimester. This is so called genetic screening, which allows to reveal pathology even at the stage of intrauterine development.
In the first trimester, by means of ultrasound, characteristic areas of the fetus are measured - the nasal bone, the thickness of the collar space. Suspicion of a chromosomal defect may occur if the nasal bone is not traced or has very small dimensions, and the thickness of the collar space is more than 3 mm. In addition, the analysis of the blood of a pregnant woman measures the amount of human chorionic gonadotropin and RAPP-A protein. The results of the blood test and ultrasound are treated together.
In the second trimester of pregnancy, the blood test is checked by three indicators. Of great diagnostic value is alpha-fetoprotein, free estriol, chorionic gonadotropin. The results of the additional study are compared with the data of the first trimester. Even the best diagnostic methods sometimes show false positive results when the child is absolutely healthy.
If genetic screening has given a high probability of having a child with Down's syndrome, then more serious tests are shown. After a preliminary consultation, they can be recommended by a geneticist.
To such analyzes carry:
Such tests, as a rule, are offered to those families who have the highest percentage of the possibility of the appearance of a baby with a pathology. Invasive methods are also not recommended if the mother's age is above 35 years.
After the child was born, for diagnostic purposes, according to the indications, a chromosomal analysis is prescribed for the presence of additional genetic particles in the 21st pair of chromosomes.
At the moment, Down syndrome is an incurable pathology, but concomitant diseases such as heart disease, for example, can be successfully treated.
With this chromosomal abnormality, the delay in the development of the nervous system is very often diagnosed, therefore in the first trimester a pregnant woman is recommended to take folic acid preparations to reduce the risk of serious disorders.
After the birth of a child, if he is healthy, all efforts should be directed to his social adaptation. There are special rehabilitation centers where speech therapists-defectologists and psychologists deal with such children. To improve the results of special training, nootropic drugs are shown that stimulate the development of the nervous system. This is aminalon, B vitamins, cerebrolysin.
Malformations of internal organs may require surgery, but timely intervention increases the chances of a normal life. Therefore, a child with a chromosomal defect should be under the constant supervision of narrow specialists.
The average life expectancy of people with Down's syndrome is shorter than that of ordinary people, which is associated with a high susceptibility to various diseases. In our time, when the possibilities of medicine have increased, this pathology can exist up to 50 years, and earlier such children rarely lived until the age of ten.
Despite their peculiarities, people with Down syndrome have the right to a full life in modern society. They are extremely kind and remain trusting children for the rest of their lives.
When the germ cells are formed during meiosis, the pair chromosomes must diverge, but if for some reason this does not happen, a third 21-chromosome( trisomy).
An abnormality occurs in approximately one in 800 newborns and in 88% of cases this occurs because of the non-separation of female gametes.
Risk Factors for the Birth of a Child with Down Syndrome
Why develops Down's Syndrome, and what is it? The main risk factor that increases the likelihood of a child with Down's syndrome is the age of the expectant mother. At 45, the risk of having a sick child is 1:30.
Although, according to statistics, children with this anomaly are born more often in young women, which is explained by the large number of births. The age of the father does not affect the appearance of pathology. This is due to the fact that male sex cells are updated every 72 days and do not accumulate toxic substances.
In women, the ovaries are kept in the ovaries from the moment of birth, which means that contacts with harmful chemicals, radiation, and the abuse of alcohol and smoking can negatively affect them.
If the family already has one "solar" child, then there is a low probability of birth( on average 1%) and a second baby with Down syndrome. Also, the risk of trisomy in the offspring may increase the kinship of the parents.
Causes of Down Syndrome
Down syndrome occurs as a result of abnormal cell division, when unnecessary genetic matter is glued to the 21st pair of chromosomes.
Pathology can have three versions: trisomy, mosaicism, translocation. The most common is trisomy, caused by non-dissociation of chromosomes during the period of cell division. Three chromosomes instead of two are observed in all cells of the child. The exact cause of this phenomenon is unknown until now.
Mosaicism is a more rare and mild form of the syndrome and differs in that not all cells have an additional chromosome, only some tissues and organs are affected. Nondisjunction arises not in the formation of the reproductive cells of parents, as in the first case, but in the early stages of embryo development.
With translocation during cell fusion, a part of one chromosome in the 21st pair is displaced to the side of another chromosome.
Symptoms and Symptoms of Down Syndrome
Usually Down syndrome is defined by a number of external symptoms that are not difficult to detect in humans:
- is a flat face with slanted eyes, as in the Mongoloid race( formerly called "Mongolism");
- small head and short neck;
- wide hand brushes with short fingers and a single transverse fold on the palm;
- short limbs;
- underdeveloped ears;
- presence of epicanth - a special fold at the inner corner of the eye that covers the lacrimal tubercle and does not pass to the upper eyelid;
- flat broad nose bridge and short nose;
- change in the iris of the eyes and presence of Brushfield spots on it - focal seals of connective tissue with a diameter of 0.1 to 1 mm, having a yellow color;
- low growth;
- skin fold on the neck of the newborn;
- strabismus;
- abnormally large language( macroglossia);
- muscle hypotension;
- shortening of fingers due to underdevelopment of middle phalanges, as well as a defect in the development of the 5th finger( curvature);
- keel-shaped or funnel-shaped chest;
- open mouth due to reduced muscle tone.
Diagnosis of Down Syndrome
Pathology is usually detected before the birth of a child. Future mothers are offered to undergo a comprehensive test, which is conducted between the 11th and 13th week of pregnancy, and between the 15th and 20th week in the second trimester. This is so called genetic screening, which allows to reveal pathology even at the stage of intrauterine development.
In the first trimester, by means of ultrasound, characteristic areas of the fetus are measured - the nasal bone, the thickness of the collar space. Suspicion of a chromosomal defect may occur if the nasal bone is not traced or has very small dimensions, and the thickness of the collar space is more than 3 mm. In addition, the analysis of the blood of a pregnant woman measures the amount of human chorionic gonadotropin and RAPP-A protein. The results of the blood test and ultrasound are treated together.
In the second trimester of pregnancy, the blood test is checked by three indicators. Of great diagnostic value is alpha-fetoprotein, free estriol, chorionic gonadotropin. The results of the additional study are compared with the data of the first trimester. Even the best diagnostic methods sometimes show false positive results when the child is absolutely healthy.
If genetic screening has given a high probability of having a child with Down's syndrome, then more serious tests are shown. After a preliminary consultation, they can be recommended by a geneticist.
To such analyzes carry:
- 1) Amniocentesis. The procedure is performed at the 15th week of pregnancy by introducing a special needle into the woman's uterus to take a sample of the amniotic fluid. This method is considered the most accurate survey.
- 2) Investigation of chorion villi. For chromosomal analysis, placental cells are selected. The test is informative between the 9th and 14th week of pregnancy.
- 3) Cord blood analysis. Such a study is conducted after the 18th week.
Such tests, as a rule, are offered to those families who have the highest percentage of the possibility of the appearance of a baby with a pathology. Invasive methods are also not recommended if the mother's age is above 35 years.
After the child was born, for diagnostic purposes, according to the indications, a chromosomal analysis is prescribed for the presence of additional genetic particles in the 21st pair of chromosomes.
Treatment and prognosis for Down Syndrome
At the moment, Down syndrome is an incurable pathology, but concomitant diseases such as heart disease, for example, can be successfully treated.
With this chromosomal abnormality, the delay in the development of the nervous system is very often diagnosed, therefore in the first trimester a pregnant woman is recommended to take folic acid preparations to reduce the risk of serious disorders.
After the birth of a child, if he is healthy, all efforts should be directed to his social adaptation. There are special rehabilitation centers where speech therapists-defectologists and psychologists deal with such children. To improve the results of special training, nootropic drugs are shown that stimulate the development of the nervous system. This is aminalon, B vitamins, cerebrolysin.
Malformations of internal organs may require surgery, but timely intervention increases the chances of a normal life. Therefore, a child with a chromosomal defect should be under the constant supervision of narrow specialists.
The average life expectancy of people with Down's syndrome is shorter than that of ordinary people, which is associated with a high susceptibility to various diseases. In our time, when the possibilities of medicine have increased, this pathology can exist up to 50 years, and earlier such children rarely lived until the age of ten.
Despite their peculiarities, people with Down syndrome have the right to a full life in modern society. They are extremely kind and remain trusting children for the rest of their lives.