What is Down Syndrome?

Down syndrome is a condition in which an individual is born with 47 chromosomes as a result of the failure of the 21st chromosome pair to separate due to reasons that are not clearly determined.
Due to this difference, individuals experience some problems in mental and physical development. In addition, heart and lung infections, stomach problems, vision and hearing disorders may occur in children.

Causes of Down Syndrome?

Each individual cell consists of 23 pairs of chromosomes. One of the chromosomes in each pair comes from the mother and the other from the father. Down syndrome occurs when 21 chromosomes fail to separate during fertilization and remain double. As a result, a cell with 24 chromosomes instead of 23 is formed. While normally there should be 46 chromosomes, individuals with Down syndrome are born with 47 chromosomes. This causes various differences. Down syndrome occurs as a result of a genetic difference. Although studies are ongoing, the cause of this difference is not yet known for certain. Although Down syndrome is a genetic difference, it is not hereditary.
The most important thing to know is that Down syndrome is not a disease but a genetic difference.

What are the symptoms of Down syndrome?

Down syndrome symptoms can be specific to each individual. It often causes physical, cognitive and behavioral changes. The most frequently used methods are physical examination and genetic testing.

Physical Symptoms of Down Syndrome

• Little hands and feet
• Having a single symian line on the palm
• Short
• poor muscle tone
• Too much space between the big toe and the second toe
• nuchal translucency
• Blunt and short fingers
• flat nasal bone
• Slightly slanted almond eyes

In addition, babies with Down syndrome experience difficulty in sucking and loose muscles after birth. Newborn jaundice is common in these babies. Chromosome analysis is performed by taking blood from the suspected baby.

Cognitive and Behavioral Symptoms Seen in Down Syndrome

• Lagging behind in language development and speaking ability
• Delays in gross motor development such as sitting, crawling and walking
• Delays in fine motor development
• Sleep problems and stubbornness
• Delays in emotional and social behavior

Types of Down Syndrome

There are 3 types of Down syndrome. These are Trisomy21, mosaic and translocation type.
TRISOMY21
It is caused by an excess of the 21st chromosome during cell division. Since chromosome failure occurs after fertilization, all cells in these individuals have 47 chromosomes. It is the most common type of Down syndrome with a prevalence of 90-95% in the world.

Translocation of Ti̇p

In the translocation type, a part of chromosome 21 breaks off and attaches to another chromosome (for example, chromosome 14). Individuals have 46 chromosomes but have genetic information for 47 chromosomes. Since there are 3 chromosomes 21 in this type, individuals have the characteristics of Trisomy21. It is the second most common type in the world with 3-5%.

Mozai̇k Tiṗp

In the mosaic type, not all cells have 47 chromosomes because the inability to divide occurs before fertilization. The number of cells with 47 chromosomes is less than the number of cells with 46 chromosomes. The number of cells with 47 chromosomes is proportional to the effects of Down syndrome. Mosaic type is the rarest type in the world with 2-4%.

Diagnostic Methods, How is Down Syndrome Diagnosed?

It can be detected during pregnancy, although not definitely, with screening tests and examinations performed during pregnancy. The first signs of Down syndrome can be seen with ultrasonography and blood tests performed in the 11th and 14th weeks of pregnancy. Fetal length, nuchal translucency, etc. are determined by ultrasonography. Symptoms such as these are being tried to be detected. Two proteins called PAPP-A and bHCG are checked in the mother’s blood. This test, known as the dual test, has an 85% chance of detecting Down syndrome.