In people with Down syndrome (trisomy 21), the 21st chromosome is present in three copies, either completely or partially. Down syndrome is characterized by developmental abnormalities affecting organs and tissues. The severity of these abnormalities varies from child to child. Early, individualized support increases the chances of leading a normal and independent life.
Below you will find additional information as well as a list of selected specialists in Down syndrome.
Experts originally referred to Down syndrome as “Mongolism.” However, this term is now obsolete.
About 50,000 people with Down syndrome live in Germany. Every year, 1,200 infants are born with this chromosomal abnormality. This means that about one in 500 children exhibits the characteristics of Down syndrome.
Down syndrome – the causes
Since neither the father nor the mother is a carrier of trisomy 21, Down syndrome is not a hereditary disorder.
The chromosomal abnormality is caused by disruptions in meiosis (the process of cell division during which sex cells mature). Egg and sperm cells develop from precursor cells during meiosis. They typically have a normal diploid set of chromosomes (46 chromosomes).
A chromosome is a molecule that contains genes and thus genetic information. A normal set of chromosomes consists of 22 pairs of autosomes (which are not involved in determining sex) and two sex chromosomes.
Normally, the genetic information of the chromosomes is distributed evenly between egg and sperm cells during meiosis. As a result, a single set of chromosomes consisting of 22 autosomes and one sex chromosome is formed. When the egg cell is subsequently fertilized by a sperm cell, a cell with a double set of chromosomes is formed again.
However, errors can occur during the division of germ cells. If both copies of a chromosome end up in the germ cell, the cell has one extra chromosome.
In the event of subsequent fertilization, the resulting cell will have 47 chromosomes instead of 46. In Down syndrome, this involves chromosome 21.
The misdistribution of this 21st chromosome during the formation of the egg is thought to be related to the mother’s age. Specifically, the risk of Down syndrome increases with the mother’s age at the time of fertilization. In addition, other risk factors that contribute to the occurrence of trisomy 21 are being discussed.
These include:
- Radiation
- Alcohol abuse
- Viral infections
- Use of oral contraceptives
Whether these factors actually have an impact is highly controversial.
The Symptoms of Down Syndrome
The extra copy of chromosome 21 leads to various developmental abnormalities in organs and tissues. The severity of these abnormalities varies from child to child.
However, the characteristic physical appearance is the same in all cases:
- A short head with a flat back of the head and a short neck
- A round and flat face
- Slightly slanted eyes
- Wide-set eyes
- A mouth that is often open
- Underdeveloped jaw and teeth
- Short, broad hands and short fingers
Physical growth is usually slower. They also have lower muscle tone and delayed reflexes.
Patients with Down syndrome often have additional physical abnormalities. For example, 50 percent of those affected have a heart defect. Many suffer from narrowing of the small intestine or rectum. People with trisomy 21 also have an increased risk of leukemia. The likelihood of developing leukemia is up to 100 times higher for children with Down syndrome.
Children with Down syndrome often learn to speak later than other children and exhibit cognitive and intellectual disabilities. While some people with Down syndrome have severe intellectual disabilities, others have average intelligence.
People with Down syndrome look different and usually have intellectual disabilities @ Drobot Dean / AdobeStock
Down Syndrome – The Diagnosis
Doctors can diagnose trisomy 21 before birth through prenatal testing. During this procedure, the doctor extracts amniotic fluid from the pregnant woman.
Experts examine the cells obtained from the amniotic fluid through chromosomal analysis. The diagnosis can also be made using the molecular biology technique known as the polymerase chain reaction (PCR).
Ultrasound scans also reveal signs that may indicate Down syndrome:
- nuchal translucency
- Fetal growth restriction
- Abnormally short femur or humerus
- Heart abnormalities
After birth, a chromosomal analysis of the child’s blood cells can provide certainty and confirm the diagnosis.
Treatment of Down syndrome
There is no cure; treatment is tailored to the symptoms that arise.
Early, individualized support increases the chances of a normal and independent life for affected children.
- A speech-language pathologist, for example, helps improve verbal communication skills.
- A physical therapist assists with muscle development.
- An occupational therapist works on physical and cognitive skills.
If other health problems are present, those affected receive medication. Surgical interventions are possible for heart defects or significant abnormalities in the digestive tract.
Down Syndrome – The Prognosis
The physical and mental limitations associated with Down syndrome vary widely. Some people with Down syndrome live independently, have their own homes, and are able to work. Others, however, are permanently dependent on care and support.
Life expectancy is lower because people with Down syndrome age prematurely and have an increased risk of leukemia. Sudden cardiac death is also more common. On average, people with trisomy 21 live to be between 50 and 60 years old.
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