Down syndrome

Down syndrome is a genetic disorder with duplication of some or all parts of chromosome 21. The other name for this disorder is trisomy 21. Each person has 23 pairs of chromosomes in their cells that make up the genetic constitution and determine a person's physical and mental attributes. Any changes or derangements in the normal makeup of chromosomes can lead to genetic diseases resulting in physical symptoms. Trisomy 21 presents with varying features, including delays in physical growth, intellectual disability with an IQ level of 50, and distinct facial features. It can be diagnosed during pregnancy. It has no cure. However, special care and education can improve the quality of life. 

Each parent of a person contributes one chromosome for each pair to make a total of 23 pairs of chromosomes. In down syndrome, an abnormality occurs during the division of chromosome 21, resulting in the total or partial copying of chromosome 21. This extra genetic material attributes to the characteristic features of down syndrome. Three mechanisms can cause this. 95% of the time, it is caused by an extra copy of chromosome 21, making up to 3 copies of chromosome 21 in all cells. The other rare mechanism is called mosaic, in which only some cells of a human have an extra copy. The 3^rd mechanism is called translocation, in which some part of chromosome 21 is attached to any other chromosome and not on chromosome 21. 

One of the most common genetic diseases in humans is Down syndrome accounting for 1 case per 1000 births globally every year. In the USA, it occurs in around 1.4 births per 1000 cases. 

Maternal age has been thought to increase the risk of having a baby with down syndrome. The more is the age, the more the probability. It has now been found that a father’s age may also be a risk factor. 

The specific features of a down syndrome baby are;

·         Small head and a small flat face with flat facial features

·         Low set small ears

·         Epicanthal folds

·         Upward-slanting eyes

·         Protruding tongue

·         Short neck

·         Short hands with a single palmar crease

Apart from the physical characteristics, other organ systems are also affected due to down syndrome;

·         Delayed growth and development

·         Congenital heart defects

·         Recurrent respiratory infections

·         Hearing and vision problems

·         Gastrointestinal problems (duodenal atresia, hirschprungs disease)

·         Dry skin

·         Premature aging

·         Leukemia (blood cancer)

During pregnancy, screening tests for down syndrome are offered to all women during prenatal visits. The screening tests may show only the likelihood of a mother carrying a down baby. If the result of these tests is positive, you will be offered confirmatory tests that can confirm the presence of a Down syndrome baby. These tests may have some adverse effects and risks. You would be given a chance to discuss the benefits, risks, and outcomes of these tests with your doctor.  The screening tests include;

 1) Blood tests that measure the levels of some hormones and chemicals that can indicate the chances of a down baby.

2) Nuchal translucency test, which identifies more than normal amount of fluid accumulation behind the baby’s neck through an ultrasound scan, pointing towards a risk of a down baby.

More specific diagnostic tests during pregnancy include;

Chorionic villus sampling (CVS): This test is usually performed between 10 and 13 weeks of pregnancy and involves taking a small sample of cells from the placenta and checking for fetal chromosomes.  

Amniocentesis: In this test, a small amount of amniotic fluid, present in the amniotic cavity that surrounds the fetus, is aspirated through a needle and analyzed for the chromosomes. It is performed after 15 weeks of pregnancy. 

After a baby is born, a diagnosis can be made by specific facial features. For confirmation, a test called chromosomal karyotype can be performed on the baby’s blood sample to check for an extra copy of chromosome 21.

Once the diagnosis is confirmed, some tests may need to be performed to evaluate the baby for all the organs systems that might be affected by down syndrome like;

·         Complete blood count

·         Bone marrow examination (to check for leukemia)

·         eye examination

·         Tests for hearing

·         Echocardiography to look for congenital heart disease

·         Ultrasound scan of the abdomen

·         X-ray chest for respiratory infections

·         Somnography to diagnose sleep apnea

·         Thyroid profile to look for thyroid disorders.

Some other disorders that need to be checked for while making a diagnosis include;

·         Congenital hypothyroidism

·         Robertsonian trisomy 21

·         Zellweger syndrome

·         Trisomy 18

The treatment of down syndrome centers around providing physical, mental, and therapeutic support to help you and your baby cope with life in an improved way. You may need to consult a team of healthcare providers, including family physicians and specialists (cardiologist, pulmonologist, endocrinologist, etc.), depending on the organ system requiring treatment.

The core concerns to be taken care of include;

·         Monitoring of Growth

·         Monitoring and providing support for cognitive development

·         Providing vaccinations

·         Providing speech therapy

·         Physiotherapy to improve muscle movements and strengths

·         Behavioral counseling to combat the emotional challenges

·         Consultation with consultants when the other organs are involved like heart problems, respiratory infections, thyroid disorders, hearing and vision problems, Alzheimer's, etc. 

Down syndrome comes with many emotional and physical challenges that need to be tackled with care. Regular screening for physical ailments is recommended to avoid complications. With proper care, one can expect to live for around 50 to 60 years. Some patients are able to attend school just like normal kids, while some may require schools for people with special needs. In the USA, around 20% of people with down syndrome are able to work and earn independently. Death may occur early in life due to complications related to the heart.  

Care and support have to be started early in life to lead a healthy and prosperous life;

·         You may need to enroll your baby as early as 3 years of age in programs available to help with motor, social, and language skills.

·         Try to enroll your baby in a school.

·         Try to be involved in other social and leisure community activities.

·         Help your baby learn basic self-help skills like changing clothes and keeping themselves clean.

·         Be ready to provide any behavioral support for emotional challenges, especially during the transition to adulthood.

·         With all the support and help, down baby can have a bright and happy future.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 17, 2023.

References

Facts about Down Syndrome | CDC

https://www.cdc.gov/ncbddd/birthdefects/downsyndrome.html#:~:text=What%20is%20Down%20Syndrome%3F,is%20born%20with%2046%20chromosomes.

Down Syndrome: MedlinePlus

https://medlineplus.gov/downsyndrome.html