Chromosomal disorders

The story of DNA

Human hereditary information is coded in the chemical language of deoxyribonucleic acid (DNA). DNA is stored in the structures of the cell nucleus, in the chromosomes. Any nucleus of a healthy human cell contains 46 chromosomes arranged in pairs (23 chromosomes coming from the father and 23 originating from the mother). To facilitate identification, individual chromosomal pairs are designated by numbers from 1 to 22. The last pair of chromosomes is made up of sex chromosomes. They are labelled as X and Y. If a XX pair is present, the individual is female, in the case of a male we find an XY pair.

In every single healthy cell, there are 46 chromosomes arranged in pairs. Sometimes, however, there occurs a random error of division and instead of a pair of chromosomes, there is a triplet present in the cell – in such a case we talk of trisomy or a chromosome may be missing in the pair, and then we are looking in a case of monosomy. Any change in the number of chromosomes may have a serious impact on the further development of the fetus. Similarly, a random error may result in the loss (deletion) or multiplication (duplication) of a specific part of the chromosome, causing subchromosomal aberration.

Trisomy – random division error

Trisomy is not a genetic disorder with family history inherited from ancestors. It is almost always a new error that occurs in the early stages of embryonic development. The risk of trisomy increases with the age of the future mother. The best-known trisomy is trisomy 21, causing the so-called Down syndrome Trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome) are significantly less frequent. Sex chromosome (X and Y) number disorders are common, too. The risk of this particular disorder is investigated by trisomy test XY.

Approximate age risk for women concerning the childbirth for a child with Down syndrome

1 in 1,000

women aged

1 in 100

women aged

1 in 10

women aged

Which chromosomal
disorders do we test?

Chromosomal disorders can cause a large number of diseases with a serious clinical picture and poor prognosis. Our tests investigate the most frequently found chromosomal disorders.

Down syndrome – trisomy 21

The cause of Down syndrome is trisomy 21 – a disease caused by the redundant chromosome 21. Only two-thirds of pregnancies with detected Down syndrome end in normal delivery. Approximately 30% of these pregnancies result in spontaneous miscarriage. The disease has a serious impact on overall growth and thriving of the child, as well as the formation of the body proportions. It is associated with a characteristic facial expression and a disorder of mental and psychological functions of varying degrees. Immune, circulatory or gastrointestinal disorders represent another common complication. Children with trisomy 21 require special medical care depending on the extent of the disability. However, in some cases, Down syndrome can be milder and allows the patient to live a long life.

Edwards syndrome (trisomy 18)

Edwards syndrome develops as a result of trisomy of chromosome 18. The consequences of this chromosomal disorder are severe – the baby is born with a low birth weight, has an abnormally shaped head, small jaw, small mouth, and suffers from frequent cleft lips and palate. The newborn has difficulty breathing, eating, and cardiac disorders may also be associated. The prognosis is very unfavorable. Pregnancies associated with Edwards syndrome are accompanied by a high rate of abortion and most live newborns do not survive for more than 1 year.

Patau syndrome – trisomy 13

If there occurs trisomy of chromosome 13, we are looking at a case of Patau syndrome. Trisomy 13 is a severe genetic disease that can affect all organs in the body, including the brain, heart and kidneys. Babies may be born with a cleft palate and deformed limbs. Newborns with this birth defect have very little chance of survival. Pregnancies with Patau syndrome are characterized by a high risk of spontaneous miscarriage or stillbirth.

Test overview