Down syndrome, also known as trisomy 21, is a chromosomal disorder. Affected people have three copies of chromosome number 21 – each person usually only has two. The surplus genetic material influences physical and mental development. How serious the effects are varies from person to person.
In this article you will read about what is down syndrome, causes, symptoms, prevention, treatment and life expectancy for down syndrome.
Quick overview:
- What is Down Syndrome? Not a disease, but a genetic anomaly. This means that the genetic make-up of those affected deviates from the “normal state”.
- Causes: There are three (instead of two) copies of chromosome 21 in all or some body cells of those affected. That is why Down syndrome is also called trisomy 21.
- Typical symptoms: Short head, flat back of the head, round and flat face, slanting eyes with a delicate crease in the inner corner of the eye, mostly open mouth with increased salivation, four-finger furrow, sandal gap, short stature.
- Possible consequences: Heart defects, malformations in the digestive tract, orthopedic problems (such as flat feet), hearing and visual disorders, increased susceptibility to infections, sleep-related breathing disorders, increased risk of leukemia, epilepsy, autoimmune diseases, autism, ADHD, etc., mental disabilities, but also special skills such as musical talent.
- Treatment: Targeted individual support (as early as possible), for example by means of physiotherapy, ergotherapy and speech therapy ; surgical treatment of organ and skeletal malformations; Treatment of comorbidities.
- Life expectancy for down syndrome: The life expectancy of people with Down syndrome depends on the severity of the manifestations and averages 50 years or more.
Life expectancy for down syndrome is higher, but not for everyone.
Symptoms of Down syndrome
People with Down syndrome (trisomy 21) can usually be recognized by their typical appearance. Characteristic Down syndrome symptoms are:
- Short head with a flat back, short neck and round, flat face.
- Slightly slanting eyes with a delicate skin fold on the inner corner of the eye.
- Bright, white spots of the iris – they disappear with increasing age and the accumulation of color pigments in the iris.
- Flat, broad bridge of the nose.
- Mostly open mouth and increased salivation.
- Ridged tongue that is often too large and sticks out of the mouth.
- Narrow, high palate.
- Underdeveloped jaws and teeth.
- Small, deep set, rounded ears.
- Excess skin on the back of the neck, short neck.
- Short broad hands with short fingers.
- Four finger crease (transverse crease on the palm of the hand, starting under the index finger and continuing to below the little finger).
- Sandal gap (large gap between first and second toe).
Slanted eyes and a flat bridge of the nose are found not only in people with Down syndrome, but also in the Mongolian tribe. That is why Down syndrome was popularly referred to as “mongolism” and those affected as “mongoloid”. For ethical reasons, however, these terms should no longer be used.
Other Down syndrome features include underdeveloped muscles (low muscle tone) and delayed reflexes. People’s body growth is slower and they are shorter than average (short stature). In addition, a pronounced weakness in the connective tissue makes the joints excessively flexible.
Health consequences of Down syndrome
Trisomy 21 can affect health. Particularly common trisomy 21 features are heart defects. They occur in about half of all people with Down syndrome. A common heart defect is the so-called AV canal. This is a defect in the septum between the atria and ventricles. It causes shortness of breath, growth disorders and recurrent pneumonia. In many cases, the cardiac septum between the chambers of the heart is not completely closed.
Very often, Down syndrome is also associated with malformations in the gastrointestinal tract , such as narrowing of the small intestine or malformations of the rectum. Hearing and vision problems are also common.
Because the immune system is underdeveloped, those affected are more susceptible to infections, especially in the respiratory tract. For example, many Down syndrome children are prone to otitis media, bronchitis and pneumonia.
In many cases, trisomy 21 is accompanied by a sleep-related breathing disorder (obstructive sleep apnea), sometimes accompanied by snoring : the upper respiratory tract relaxes and narrows during sleep, resulting in short breathing pauses. The oxygen saturation in the blood drops each time. The brain reacts to this with a wake-up impulse.
However, those affected fall asleep again quickly and usually cannot remember the brief wakefulness the next day. However, they are often tired during the day because they lack restful, continuous sleep.
Another consequence of trisomy 21 is the increased risk of acute leukemia (a form of blood cancer): it is up to 20 times higher than in children without this chromosomal abnormality. There are several genes on chromosome 21 that play an important role in the development of leukemia.
The so-called acute myeloid leukemia (AML) is more common in Down syndrome than acute lymphocytic leukemia (ALL) – in children without trisomy 21 it is exactly the opposite.
In addition to leukemia, epileptic seizures (epilepsy) and autoimmune diseases are more common in Down syndrome than in the general population. The latter include, for example:
- Type 1 diabetes mellitus.
- Celiac disease.
- Chronic rheumatic disease in childhood (juvenile rheumatoid arthritis, also called juvenile idiopathic arthritis).
- Autoimmune thyroid diseases (such as Hashimoto’s thyroiditis).
In addition, orthopedic problems are often observed in trisomy 21. These include, for example, malpositions in the neck and shoulder area as well as on the hip (hip dysplasia), an unstable kneecap and malformations in the foot area (such as flat feet).
In addition, people with Down syndrome have an increased risk of behavioral problems or psychiatric disorders, such as ADHD, autism, anxiety disorders and emotional problems up to and including depression.
Down syndrome also affects fertility : boys and men with trisomy 21 are usually sterile (infertile). Affected girls and women, on the other hand, are fertile (albeit to a limited extent). The probability that they will pass on the chromosomal abnormality to the unborn child during pregnancy is around 50 percent.
Down Syndrome: Mental Restrictions
Down syndrome is the most common cause of congenital intellectual disability. Trisomy 21 children often learn to speak later than other children, partly because their hearing is usually worse. Their language is therefore sometimes difficult to understand. In many cases, those affected need longer to understand a situation.
They often find it difficult to retain what they have already learned when they have to learn something new. Motor development is delayed – children start crawling or walking late.
Intellectual abilities are more or less limited. Some sufferers are severely mentally impaired (which is relatively rare), while others are of near-average intelligence. The following applies: The mental development of a Down syndrome child not only depends on its genetic make-up, but also on whether and to what extent it is encouraged.
Down Syndrome: Special Abilities
Trisomy 21 does not only mean malformations and limitations. People with Down syndrome have strong emotional abilities and a sunny nature: they are loving, tender, friendly and cheerful. In addition, many are musically gifted and have a keen sense of rhythm.
Causes of Down syndrome
what causes down syndrome?
Down syndrome is due to an error in the production of egg cells or sperm:
Egg and sperm cells are created by cell division from progenitor cells with a normal double set of chromosomes (chromosomes = carriers of the genetic material). This double set of chromosomes includes 22 paired autosomes plus two sex chromosomes (XX in females and XY in males). So there are 46 chromosomes in total.
During the division process, the genetic information is normally evenly distributed to the developing germ cells, which then each have a simple set of chromosomes (22 autosomes and one sex chromosome = 23 chromosomes).
In the event of later fertilization, the fusion of egg cell and sperm can produce a cell with a normal double set of chromosomes, from which the child then emerges after countless cell divisions.
However, mistakes can happen when the 46 chromosomes are distributed among the developing germ cells: Sometimes the two copies of a chromosome accidentally end up in one and the same new egg cell. This then has a total of 24 instead of 23 chromosomes.
If it later fuses with another “normal” germ cell during fertilization, the result is a so-called trisome cell – it contains three copies of the relevant chromosome – i.e. a total of 47 chromosomes.
In Down syndrome, there are three (rather than two) copies of chromosome number 21. Doctors distinguish between different forms of Down syndrome : free trisomy 21, mosaic trisomy 21 and translocation trisomy 21.
Free trisomy 21
All body cells are equipped with a third chromosome 21. It is almost always a spontaneous new mutation. This means that the free trisomy 21 usually develops randomly, i.e. without any apparent reason.
About 95 percent of all people with Down syndrome have a free trisomy. This is by far the most common variant of the chromosomal disorder.
Mosaic trisomy 21
Sometimes the superfluous third chromosome 21 is lost again during cell divisions during embryonic development in one cell (“trisomy rescue”), but not in others. This means that “normal” and trisome cell lines develop as a result. So the child’s body consists of cells with 46 and cells with 47 chromosomes.
The result is the same if fertilization takes place normally (i.e. the fertilized egg cell has 46 chromosomes), but an error occurs in the subsequent embryonic development: During the division of a single cell, three chromosomes 21 can accidentally be left in a daughter cell (and only one copy land in the second daughter cell). Here, too, both “normal” and trisome cell lines subsequently develop.
Mosaic trisomy occurs in about two percent of all people with Down syndrome. Depending on whether the person concerned has more “normal” or more trisome cells, the Down syndrome characteristics are pronounced to different extents.
Translocation trisomy 21
This form of Down syndrome usually has its origins in one parent with a so-called “balanced” translocation 21. That means: The affected parent normally has two copies of chromosome 21 in his body cells. However, one of them is attached to another chromosome.
There are no consequences for the parent himself. When a child is conceived, however, an “unbalanced” translocation 21 can occur: the child then has three copies of chromosome 21 in all body cells, one of which is attached to another chromosome.
A translocation trisomy 21, which originates from a balanced translocation of one parent, can occur more frequently in one family. This means that several children of the affected parent can have Down syndrome (in the form of translocation trisomy 21).
Only rarely does a translocation trisomy 21 arise spontaneously either shortly before or after fertilization of the egg cell.
Translocation trisomy 21 accounts for about three percent of all cases of Down syndrome.
Risk factors of Down syndrome
In principle, with every pregnancy there is a possibility that the child will be born with Down syndrome (or another genetic disorder). However, the probability of this increases as the mother ages. In women aged 35 to 40, 1 in 260 children is born with trisomy 21. For 40 to 45-year-old pregnant women, the ratio is already 1 to 50.
Scientists suspect that egg cell division is more prone to disruption as women get older. This could make it easier for errors in the division of the chromosomes to occur. Whether the father’s age also plays a role is controversial.
Researchers are discussing other factors that may contribute to the occurrence of Down syndrome. These include, on the one hand, endogenous (internal) factors such as certain gene variants.
On the other hand, exogenous (external) influences are also suspected, for example harmful radiation, alcohol abuse, excessive smoking, taking oral contraceptives or a viral infection at the time of conception. However, the importance of such factors is disputed.
Diagnosis of Down syndrome
As part of prenatal diagnostics, it can be determined before birth whether a child has Down syndrome (or another chromosomal disorder or genetic disease). Several investigation methods are possible:
The so-called non-invasive procedures such as the first trimester screening (ultrasound and blood test) and the triple test (blood test) are risk-free for mother and child. In particular, the first trimester screening (at the end of the first trimester of pregnancy) provides good indications of trisomy 21 in the unborn child, but does not allow a reliable diagnosis. As a result, the screening only provides an estimate of how high the risk of “Down syndrome” is in the unborn child.
In order to be able to diagnose Down syndrome with certainty, a direct analysis of the child’s chromosomes is necessary. The sample material is obtained from a tissue sample from the placenta (chorionic villus biopsy ), an amniotic fluid test (amniocentesis) or a fetal blood sample (umbilical cord puncture).
All three procedures are interventions on the womb (invasive methods). They are associated with a certain risk for the child. That is why they are only used in specific cases of suspicion, for example when the ultrasound findings are unclear.
Also in pregnant women The risk of miscarriage as a result of the procedure and the risk of Down syndrome from the age of 35 cancel each other out. Therefore, pregnant women from this age are offered an amniotic fluid test.
The procedures in detail
Ultrasound (sonography): The first sign of trisomy 21 is often a thickened nuchal fold in the fetus (nuchal translucency test, nuchal fold measurement). This is a temporary swelling in the neck that occurs between the 11th and 14th week of pregnancy. It indicates a chromosomal disorder in the child.
In addition, the doctor can use the ultrasound to detect internal and external malformations or special features that may be caused by an excess chromosome 21. Examples are a shortened nose bone, a small head, short hands and feet or the sandal gap.
With a special ultrasound method (Doppler sonography) the blood flow in the heart and the large heart vessels can be shown. This allows the doctor to detect heart defects, which are quite common in Down syndrome.
First trimester screening: Here certain measurement results from the ultrasound examination (including nuchal translucency test), a blood test with the determination of two values (HCG and Papp-A) as well as individual risks such as the age of the mother or a family history are summarized. This results in a statistical value for the risk of trisomy 21 in the unborn child.
Triple test: First, three parameters are measured in the maternal blood serum – the child ‘s protein alpha-fetoproptein (AFP) and the maternal hormones estriol and hCG. The risk of trisomy 21 in the child can be calculated from the measurement results together with the age of the mother and the time of pregnancy.
Chorionic villus biopsy : The chorionic villi are part of the placenta. A tissue sample is obtained from them for chromosome analysis. The chorionic villi have the same genetic material as the unborn child because they also come from the fertilized egg cell. The examination can be carried out from about the 11th week of pregnancy.
Amniocentesis (amniotic fluid test): The doctor uses a fine hollow needle to take a sample of the amniotic fluid from the abdominal wall of the expectant mother. A few childlike cells swim in it. Your genes can be tested in the laboratory for genetic disorders such as trisomy 21. An amniotic fluid test is possible from the 14th week of pregnancy at the earliest.
Fetal blood collection: The doctor takes a blood sample from the unborn child from the umbilical cord (umbilical cord puncture). The cells contained are examined for their chromosome number. The earliest possible time for an umbilical cord puncture is around the 19th week of pregnancy.
PrenaTest and Panorama test
Until a few years ago, trisomies such as Down syndrome in an unborn child could only be diagnosed using invasive methods of prenatal diagnostics (chorionic villus sampling, amniocentesis, fetal blood sampling). However, these procedures can cause a miscarriage when the sample is taken.
There are now some special blood tests available for diagnosing trisomies in unborn babies, such as the Prena test or the Panorama test: They can also detect Down syndrome and other chromosome disorders with a high degree of probability, but without increasing the risk of miscarriage.
The PrenaTest, the Panorama test and similar blood tests are based on the fact that traces of the child’s genetic material can also be detected in the blood of a pregnant woman. These “snippets” of DNA from the unborn child can be filtered out and examined for Down syndrome and other chromosomal abnormalities.
Harmony Test
Like the PraenaTest and the Panorama test, the Harmony test is part of non-invasive prenatal diagnostics (NIPD ). It is also suitable for detecting Down syndrome and other chromosomal abnormalities in the unborn child with a high level of certainty.
The Harmony test (like comparable blood tests) is intended for pregnant women with an increased risk of chromosomal abnormalities in the unborn child. This can be the case, for example, if the first trimester screening has produced an abnormal result or Down syndrome or other chromosomal abnormalities already run in the family.
So far, the Harmony test and the other non-invasive blood tests used in prenatal diagnostics have usually not been paid for by health insurance companies.
Treatment of Down syndrome
The excess chromosome 21 can neither be blocked nor switched off – this means that Down syndrome cannot be cured. However, affected children benefit from consistent care and support. The aim is to reduce limitations (such as problems with fine motor skills) and to fully exploit the individual development opportunities of children with Down syndrome. In addition, health problems associated with trisomy 21 should be treated as best as possible (e.g. heart defects).
The prerequisite for this is that the targeted funding is started as early as possible. This increases the chance that children with trisomy 21 will later be able to live as independently and autonomously as possible.
Below you will find some examples of therapy and support options for Down syndrome. Each child should receive individual, appropriate treatment, tailored to their own needs.
Surgery
Some organ malformations such as malformations in the rectum and heart defects can be surgically corrected. This can significantly improve the quality of life of those affected. Surgical intervention is also often useful for orthopedic problems, for example in the case of unstable kneecaps or foot malformations.
Physiotherapy & occupational therapy
Physiotherapy (e.g. according to Bobath or Vojta) supports the motor development of Down syndrome children. Weak muscles and loose connective tissue are strengthened and trained. The coordination of body movements and posture control can also be improved with suitable physiotherapeutic measures. Occupational therapy can also support the fine motor skills and perception of the children.
The choice of therapist (the child must trust him or her) and an individually tailored therapy plan are decisive for the success of the treatment. It is also important that the exercises are approached in a playful way and that the child is not put under high pressure to perform.
Language promotion
Language development in Down syndrome children can be promoted in a number of ways. The children’s ability to communicate and express themselves can be improved with language and speaking exercises (at home and in their own language lessons – speech therapy).
It also helps if others speak to you slowly and clearly. It is best when gestures support what is being said. Children with Down syndrome can memorize visual impressions more easily than information that they only absorb through their ears. The use of signs can promote language acquisition from around the age of two.
Hearing impairment impairs the ability to learn to speak. Therefore, it should be treated early. The high, pointed palate typical of Down’s syndrome and misaligned teeth can be partly to blame if those affected are unable to speak properly. A dentist or orthodontist can help here.
Spiritual and social advancement
One’s own family and circle of friends are very important for people with Down syndrome. In this environment, they can best learn and practice social behavior.
If possible, children with Down syndrome should attend an integrative kindergarten. Such facilities accommodate both healthy children and children with physical or mental disabilities. In addition to educators, specially trained staff work there who specifically support the children.
At school, children with Down syndrome often cannot keep up with the rest of the class. They need longer and more practice to learn something new. A sensible alternative could be, for example, integration classes or schools for people with learning disabilities.
Patience and empathy
Children with Down syndrome are capable of learning – they just need a lot of time and empathy. They usually react very sensitively to pressure and excessive demands and turn away.
Accompanying diseases of trisomy 21 such as epilepsy, sleep apnea or leukemia are treated in a targeted manner.
Down syndrome: course and prognosis
Down syndrome can affect mental and physical development in very different ways. In some cases, independent living with Down syndrome in adulthood is possible. However, there are also those affected who, due to severe mental disabilities, are dependent on permanent care for the rest of their lives.
Individual early support and careful medical care from birth are always decisive for the good development of children with Down syndrome.
Life expectancy for down syndrome
Few studies have succeeded in determining the life expectancy for down syndrome. The prognosis for Down syndrome depends primarily on the risk of leukemia and the type of heart defect.
However, most heart defects can now be treated effectively. In addition, people with Down syndrome are more susceptible to infections. Because of these factors, childhood mortality is highest. Adults with Down syndrome age prematurely, and their mental capacity also declines early.
Despite everything, it has been possible to increase the life expectancy of those affected in recent decades – thanks to improved support and care as well as the treatment of comorbidities. In 1929, Down syndrome children lived to an average age of just nine years. Studies for 2002, on the other hand, showed an average life expectancy of 60 years.
