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The frequency of trisomy 21 is 1 / 700 births. The boys are all affected than girls. The actual incidence is much higher but 6 out of 7 embryos or fetuses carrying trisomy 21 die in utero (abortion spontaneous).
Causes and Risk Factors
The cause of this condition is unknown.
meiosis could lead to a result of nondisjunction of unknown cause, two germ cells (oocytes): one with 24 chromosomes (two chromosomes 21 instead of one) and one with 22 chromosomes (no chromosome 21).
If the egg with two chromosome 21 is fertilized by a sperm normal, it results in an embryo carrying three chromosomes 21. More
mother is elderly, the greater the risk of poor distribution of chromosomes during meiosis is high: 1 / 100 after 40 years and 1 / 46 after 45 years. Between 20 and 25 years, the risk is 1 / 1600.
As many more mothers with children between 20 and 25 between 40 and 45, it is not uncommon to find children of young mothers with Down syndrome.
In 95% of cases, it is a free chromosome in 3% of cases, there is a translocation, and 2% of cases, a mosaic.
For all women at risk (the elderly woman, existence of trisomy in the family etc..), Amniocentesis and prenatal diagnosis allows the possibility of abortion.
signs of trisomy 21
The diagnosis is not always evident in the newborn. It is based on a set of characters never wholly present, but that will give all such infants and children a "family resemblance"
• A variable degree of mental retardation (IQ 20 to 80 with a mean of 50 )
• Psychomotor retardation: sitting held to 1 year, walking to 2 years ... etc.
• A gentle and affectionate
• Small size;
• A flat neck;
• A flat face, round with a broad nose;
• Slots oblique palpebral, external angle being higher that the internal angle;
epicanthus • A (small fold at the inner corner of the eye);
• Small white spots in the iris (Brushfield)
• Small little hemmed ears;
• Small mouth with a tongue that tends to emerge;
• Small teeth delayed onset;
• A short neck with excess skin on the neck;
• A muscular hypotonia;
• A big belly with umbilical hernia;
• A short fifth finger;
• A single palmar crease;
• The dermatoglyphics evocative (tri-radius at t "etc.).
• A very big toe separated from the 2 °.
Psychomotor development
Psychomotor development was slow on the whole. Acquisitions are hampered by hypotonia and hypermobility constants. During the first months of life, babies are loving, quiet, quiet, little crying and sleeping a lot. They walk between 2 and 3 years and talk about 4 to 5 years.
From 6-7 years, instability motor, intellectual and emotional emerges. These problems contrast with the preceding phase of passivity. The mongoloid child is a child magnet gay social contacts, but likely greedy.
The mental retardation is constant. Acquisitions are often limited to teaching basic reading and addition. The child with Down syndrome is especially sensitive to conditioning.
Complications
Statistically, children with a trisomy 21 have a clear tendency for ENT infections. Congenital heart defects (atrioventricular canal, ventricular septal etc. ...), leucosis acute respiratory infections repeatedly, cataracts, duodenal atresia, Hirschsprung's disease appear also more frequent.
Treatment
It advises nursery school until 5 or 6 years since the emulation among the other children is beneficial. Then the child is directed to a Medico-Pedagogical Institute (IMP) and a Professional Medical Institute (IMPro). The manual training is possible.
Dr. Lyonel Rossant, Dr. Jacqueline Ross-Lumbroso
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