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Down syndrome is a genetic disorder that occurs when an individual has a full or partial extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome.
The clinical phenotype of Down syndrome is marked by varying psycho-physical anomalies and an increased incidence of certain systemic diseases. These manifestations can differ greatly among individuals, influenced not only by genetic factors but also by environmental factors such as education and family upbringing.
Individuals with Down syndrome often exhibit distinct physical characteristics. These may include a small skull with a flattened occipital region, a rounded face with a flattened profile, small and round ears with low insertion, short fingers, and muscular hypotonia at birth. Other common characteristics include a short nose with a flat root, small and irregular teeth, a voluminous tongue, and palms crossed by a single transverse groove.
Individuals with Down syndrome are also at a higher risk of certain systemic diseases. These can include cardiovascular diseases, malformations of the digestive tract, leukemia, alopecia, growth retardation, overweight/obesity, eye diseases, immune system problems, hypothyroidism, ear diseases, and orthopedic diseases.
Mental retardation is a constant aspect of Down syndrome, varying in degree from mild to medium, with a tendency to worsen with age. Moreover, individuals with Down syndrome develop the neuropathological signs of Alzheimer's disease at a much earlier age than normal individuals.
The risk of having a child with Down syndrome increases as the maternal age increases. Therefore, screening for Down syndrome during pregnancy is crucial. Modern science offers numerous tools to better characterize this risk.
The "triple test" is a screening method based on the measurement of three markers in serum: alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol. The "quad test" adds an additional serum marker, inhibin A, to the triple test. These tests can identify 50 to 80% of cases of Down syndrome, with the risk of false positives around 5%.
Amniocentesis and chorionic villus sampling are invasive tests used for the early diagnosis of Down syndrome. These tests are generally performed when the triple or quad test shows a high risk of carrying a fetus with Down syndrome. Despite the risk of miscarriage, these tests have a diagnostic accuracy close to 99%.
Early intervention is vital to fully exploit the psycho-physical development potential of children with Down syndrome. Children with Down syndrome can learn to carry out activities usually performed by other children, such as playing, speaking, building, and playing sports, although this may require longer learning times.
Family involvement and support from various associations are crucial in the care and treatment of individuals with Down syndrome. It's important to remember that while Down syndrome is a part of the individual's identity, it does not define them. With the right support, individuals with Down syndrome can lead fulfilling lives.