What is Down Syndrome?

Down syndrome, also known as trisomy 21, is the most common genetic disorder.  It is caused by a change in the number of chromosomes.

Down syndrome is a natural human condition, not a disease. Syndrome, or a combination of symptoms that have a common cause. Down syndrome is not inherited genetically.

 

 

Down Syndrome Statistics / Prevalence

According to statistics, one in every eight hundred children worldwide is born with Down syndrome. People with Down Syndrome can be found everywhere, anywhere in the world, in any ethnic, cultural or social group.

 

 

Who diagnosed and described Down Syndrome

In 1866, the English physician John Langdon Down first described the characteristic feature of this syndrome, which was later renamed Down Syndrome.

In 1959, the French geneticist and pediatrician Jerome Lejeune discovered that in the case of Down syndrome, the 21st pair of chromosomes contained an extra chromosome. Accordingly, each cell consists of 47 chromosomes instead of 46. On chromosome 21, instead of two, three chromosomes are laid out, so it is otherwise called free trisomy or trisomy 21 (trisomy or trebling).

 

 

What is a chromosome?

The chromosome is part of the cell nucleus. Genes are located along its entire length, which contains information containing the hereditary traits of the organism and through which this information is passed from one generation to another.  Humans have 46 chromosomes in each cell, 23 pairs in which one chromosome is maternal and the other is paternal.  

 

 

Forms of Down syndrome

 

Trisomy 21 is the most common form and is found in 95%. There are two more other forms of Down syndrome:

•             Translocation, which occurs in 3-4% of cases. In this case, extra chromosome 47 is not "free" and goes to any other chromosome.

•             Mosaicism, which is very rare and is found in 1-2%. At this time, some cells contain 47 chromosomes and some contain a normal number of chromosomes - 46.

 

 

Signs of Down Syndrome

It is the above, additional genetic material that creates the characteristic feature of Down syndrome and is found in 47-82% of cases:

•             Indirect eyelid wrinkle (epicanthic fold)

•             Flat profile of the face (lunar shape)

•             Different shape of the ear canal (small, wrinkled ear attached to the skull)

•             Flat back of head, head (brachycephaly)

•             Open mouth with access to the corners of the lip

•             Macroglossia (large tongue)

•             Narrow high domed palate (Gothic palate)

•             Dysplasia of the middle phalanx of the fifth finger, clinodactylya (5th finger’s bent)

•             Transverse crease of the palm

•              Hypermobility of joints

•             Sandalwood wrinkle on the ankle

•             Separately standing big toe

•             Hypotension (impaired muscle tone)

•             Small white spots on the colored membrane of the eye (brushfield spots) 

 

Down syndrome is often characterized by intellectual disorders, which can be mild or moderate. However, every person with Down Syndrome is an individual, a unique person who may or may not have the listed signs / characteristics at different frequencies and degrees.

 

 

The question is often asked, how does an extra chromosome appear in a cell? 

It is believed that the presence of an extra chromosome is the result of an incorrect division of the cell, when the division of germ cells, ovum  or sperm (meiosis) does not cause the 21st pair of chromosomes to be separated from each other. Then, when two 21 chromosomes “stick" to each other, a trisomy zygote is formed after fertilization (zygote-fertilized ovum).

The cause of trisomy has been the subject of study by geneticists / scientists for many years. Numerous theories were discussed, none of which were proven. The reason why chromosome pairs do not separate from each other and why the process of cell division is disrupted is still unknown and has been the subject of research for more than a century.

Mothers often think that various viral infections, pathologies, medications, or abnormalities transmitted during pregnancy have caused a chromosomal change in the fetus, when in fact the ovum or sperm already contained extra chromosomes in the 21st pair before fertilization!

The birth rate is higher among young women. Births of children with Down syndrome are common in this age group. In general, the likelihood of developing genetic disorders increases with age.  The age of the parent is only a risk factor and not a direct cause! 

For a link between parental age and Down syndrome, see the following link: 

 

https://www.cdc.gov/ncbddd/birthdefects/downsyndrome.html#ref

 

 

Life expectancy

The development of medicine has radically changed the pre-existing condition. The introduction of laboratory and instrumental research has enabled physicians to detect and eliminate health problems and diseases in a timely manner. In recent years, the main cause of death has been inability to diagnose, lack of surgery and antibiotic therapy.

Today, the life expectancy of people with Down Syndrome has increased significantly, which has been facilitated by proper and timely medical supervision and increasing access to the medical services they need. As a result, life expectancy is about 60 years. This means that life expectancy is the same as the average in the general population. Numerous people have reached even 80 years.

For more information follow the link:

https://academic.oup.com/eurpub/article/17/2/221/435114

 

 

development

People with Down Syndrome, like all of us, have different abilities about which a certain part of society does not have enough information. There are a number of old, erroneous opinions. Their capabilities have been significantly changed and enhanced through the involvement of family members, early development assistance, and community integration. People with Down Syndrome learn and develop at their own pace. Today, children with Down Syndrome go to public kindergartens and schools to learn to read and write. They can swim, draw, dance, play, sing and more. They can lead independent lives, study and work, succeed in sports and the arts. Many of them get married and spend time with dignity in a circle of loved ones.

It should be noted that awareness rising has significantly reduced the incidence of newborn abandonment by parents due to Down syndrome.

 

 

Diagnosis of Down syndrome

There are prenatal (pregnancy) screening tests, which are conducted in the first and second trimesters of pregnancy, so-called double and triple test. The possible risk of chromosomal abnormalities in the fetus is assessed taking into account the blood plasma analysis of pregnant women, ultrasound examination and the age of the mother.

None of the screening tests have a final diagnostic value or an accurate diagnosis is made based on them. In case of changes found in the results of the study, the obstetrician-gynecologist, geneticist determines whether the pregnant woman needs further research, chorionic villus sampling (CVS) and amniocentesis. It should be noted that these methods are associated with certain risks, such as spontaneous abortion.

As for the diagnosis of the postnatal period, cytogenetic examination is performed after the birth of the child: Chromosome analysis or karyotype determination.