After the declaration of 21 March as the World Down Syndrome Day by the United Nations, various awareness activities are organized around the world.
Down Syndrome is a chromosomal abnormality. While the number of chromosomes in an ordinary human body is 46, the number of chromosomes in individuals with Down Syndrome is 47. It occurs when an extra chromosome is included in the 21st chromosome pair as a result of incorrect division during cell division. For this reason, Down Syndrome is also known as Trisomy 21.
In the formation of Down Syndrome; There is no difference in country, nationality, socio-economic status. The only factor known to cause Down Syndrome is the age of pregnancy, the risk increases as the gestational age progresses. In our country, prenatal mothers are informed about fetal anomalies such as Down Syndrome and screening tests and USG examinations for chromosomal disorders, and necessary guidance is provided. It occurs on average one in every 800 births. There are around 6 million individuals with Down Syndrome all over the world.
There are 21 types of Down Syndrome: Trisomy 3, Translocation and Mosaic. The diagnosis of Down Syndrome is made immediately or shortly after birth. Some physical features seen in Down Syndrome; slanted small eyes, flat nose, short fingers, curled little finger, thick nape, single line on the palm, the big toe being wider than the other fingers are typical.
Individuals with Down Syndrome are more prone to certain disorders. For this reason, it is important that health checks are carried out without interruption and on time. The physical and mental development of babies with Down Syndrome is slower than their peers. However, they can successfully adapt to social life with appropriate education programs.
What Are the Symptoms of Down Syndrome?
Although individuals with Down syndrome may look alike, each may have different personal and physical characteristics. They usually have mild to moderate mental retardation and start speaking later than their peers.
Similar physical characteristics of individuals with Down syndrome can be listed as follows:
- A flat nose bridge and a flat face
- upward slanting eyes
- short neck
- Small and low set ears
- large tongue prone to protruding
- Eye white spots, also known as Brushfield spots
- small hands and feet
- Single line on palm (Simian line)
- Loose muscle tone (hypotonia) and loose joints
- Short stature in both childhood and adulthood
Developmental delay in mental and social skills in children with Down syndrome; It can cause impulsive behavior, poor judgment, shortened attention span, and slow learning.
What are Down Syndrome Types?
Down syndrome types may not be distinguished from each other without genetic analysis. There are three types:
- Trisomy 21: 95% of cases are of this type. Each cell in the body has three copies of chromosome 21.
- Translocation Down Syndrome: The mechanism in approximately 3% of individuals with this syndrome is translocation. In this type, either part or all of the extra chromosome 21 is attached to another chromosome. The extra chromosome 21 is not free.
- Mosaic Down Syndrome: It is the least common type. 2% of individuals with Down syndrome are mosaic. Mosaic means mixture or combination. In this case, some of the cells in the body carry two copies of the 21st chromosome as they should, while some cells have an extra 21st chromosome. It has similar features to other types of Down syndrome, but its symptoms are often milder.
What Causes Down Syndrome?
The formation of Down syndrome is multifactorial and is affected by many factors. However, the exact mechanism of formation has not been elucidated.
The most important known risk factor is advanced maternal age. Mothers aged 35 and over are more likely to give birth to a baby with Down syndrome than a young mother. This probability increases with increasing maternal age. A 40-year-old mother is twice as likely to have a baby with Down syndrome than younger mothers. Most mothers of babies with Down syndrome gave birth under the age of 35, this is because the number of births for women under 35 is much higher than for women over 35. Other risk factors are a family history of Down syndrome and a genetic translocation.
How is Down Syndrome Diagnosed?
There are two types of tests to detect Down syndrome during pregnancy. These are screening tests and diagnostic tests. A pregnancy screening test indicates a low or high probability of the baby having Down syndrome. They do not lead to a definitive diagnosis. However, they are more reliable tests for both the safety of the mother and the development of the baby. Diagnostic tests are more successful in detecting Down syndrome, but still do not give precise information. They are risky tests for mother and baby.
Screening Tests
It is tested by measuring the level of certain hormones and substances in the mother's blood and by ultrasound examination. They are commonly known as double, triple and quadruple screening tests. The nuchal translucency of the baby is measured on ultrasound. Screening tests can give false positive or false negative results. In other words, the baby may be born with Down syndrome when the results are normal, or the results may indicate a high risk when the baby is normal.
Dual testing, 11-14 days in the first trimester or just after. done during pregnancy. The nuchal translucency of the baby is measured on ultrasound. The levels of B-HCG and PAPP-A hormones are measured in the blood taken from the mother.
The triple test is done during the second trimester, between week 15 and week 22 of pregnancy. It gives more accurate results when the test is done between the 16th and 18th weeks of pregnancy. B-HCG, AFP (alpha fetoprotein) and estriol (E3) levels are checked in the blood taken from the mother.
Although the quad test gives more accurate results between the 15th and 18th weeks of pregnancy, it is a test that can be performed up to the 22nd week. Inhibin A level is also included in the test in addition to the hormones B-HCG, AFP and Estriol, which are also measured in the triple test.
Diagnostic Tests
Diagnostic testing is often done for confirmation after positive screening test results. Chorionic villus sampling (CVS), amniocentesis and percutaneous umbilical blood sampling (PUBS) are diagnostic tests.
Amniocentesis is done between 16 and 20 weeks of pregnancy. done before and after
In amniocentesis, the risk for mother and baby increases. In the amniocentesis test, a sample is taken from the amniotic fluid around the baby. The epithelial cells of the baby in the amniotic fluid are genetically examined. Chromosomes are counted.
Chorionic villus sampling is done between 10 and 12 weeks of gestation. A sample of the placenta is taken and examined. It stands out because it is the earliest diagnostic test among the diagnostic tests and can provide information in terms of Down syndrome in earlier stages of pregnancy. However, the probability of miscarriage after the procedure is 1-2%.
In percutaneous umbilical blood sampling, examination is made from the blood taken from the baby's umbilical cord. Preferably, it is expected that the pregnant woman will pass the 18th week of pregnancy. It stands out as it can be done at any time in the long process from the 18th week to birth. The most important complication is bleeding.
Is Down Syndrome Genetic?
A complete physical examination is performed in terms of congenital diseases common in Down syndrome. For diagnosis, a genetic analysis known as karyotype analysis is performed by taking blood from the baby. Diagnosis is made by counting 47 chromosomes and seeing three pairs of 21st chromosomes.
What are the Common Health Problems in Down Syndrome?
The frequency of major birth defects in Down syndrome is low. However, some babies may be born with one or more major birth defects and accompanying health problems. Common health problems in Down syndrome are as follows:
- Hearing loss
- Obstructive sleep apnea (temporary cessation of breathing while the person is asleep)
- Ear infections
- Eye diseases (blurred vision, cataracts)
- Congenital hip dislocation
- Leukemia
- Congenital heart diseases (hole in the heart, etc.)
- chronic constipation
- Dementia (memory problems)
- Hypothyroidism (low thyroid function)
- Obesity
- Alzheimer's disease in old age
Individuals with Down syndrome are more prone to infection. They can frequently have urinary tract infections, skin infections and upper respiratory tract infections.
Is There a Cure for Down Syndrome?
There is no cure for Down syndrome. However, it is possible to help the person and his/her family with sociocultural support and appropriate education programs. The special education program starts when the baby is 2 months old. It is aimed to develop and improve the baby's sensory, social, motor, language and cognitive skills.
It is recommended that you have the necessary screening tests and consult a gynecologist, especially if you are over the age of 35 and are considering pregnancy.