Down Syndrome

Down Syndrome

Down Syndrome Or Trisomy 21

It is a chromosomal genetic disorder in which the affected person carries an extra copy of chromosome 21. These individuals have some degree of intellectual disability, characteristic facial features and often, heart defects and other health problems.

What Causes This Problem?

It is a genetic problem in which the person carries an extra copy of chromosome 21. Each person has 23 pairs of chromosomes or 46 in all. Every individual inherits one pair from the mother’s egg and one from the father’s sperm making it a total of 46 chromosomes. Sometimes the egg or sperm may divide incorrectly causing the egg or sperm cell to have an extra chromosome 21. When this abnormal cell joins the egg/ sperm cell then the resulting embryo has 47 chromosomes instead of 46 chromosomes. This type of error accounts for 95% cases of Down syndrome. In the rest of cases it is due to a Robertsonian translocation in the parents wherein a part of long arm of chromosome 21 is attached to another chromosome. The parents may be phenotypically normal, however this form is often transmitted to the offsprings.

What Are The Health Problems Associated In A Child With Down Syndrome?

It is the most common cause of Intellectual disability in children. There is no way to predict the mental development of the child with Down syndrome based on the physical features. Also they are more likely to be affected by-
  • Heart problems : Almost 40 % of babies with Down syndrome have heart defects. These can be minor and just require medication while others are major and and reuire surgery. It is imperative that these children are seen by the paediatric cardiologist and a echocar diogram is done.
  • Intestinal problems : 12% of Down babies are born with intestinal problems which require surgery
  • Visual problems : More than 60% have vision problems such as near or far sightedness, cataracts or crossed eyes. A child should be examined by the paediatric ophthalmologist on a regular basis
  • Hearing problems : About 75% of Down children have some degree of hearing loss. They therefore need to be checked for hearing loss at birth and again within 2 months which needs to be regular to minimise the chances of language development.
  • Frequent infections like colds and ear infections. All standard immunisations need to be done
  • Thyroid problems : 1% of babies are born with congenital hypothyroidism, a hormone deficiency that can affect growth and brain development. This can be treated by oral doses of thyroid hormone. The rest can develop thyroid problems and need to be tested yearly
  • Memory loss : Down children are more likely to develop Alzeimers disease compared to unaffected individuals and at an earlier age
  • Leukemia (blood cancer) : Some children may have more of the above problems but others may have none. Does the risk of having a baby with Downs syndrome increase with age? Down syndrome can affect pregnancy at any age.
The incidence goes up with age but universal screening for Down syndrome is advocated for all pregnant women.

Can Down syndrome be cured?

There is no cure for Down syndrome

What is the risk that parents of a child with Down syndrome will have another affected child?

In general, in each subsequent pregnancy the chance of having another baby with Down syndrome is about 1:100 up to the age of 40. After age 40, the risk is based on mothers age. If however the first child has translocation Down syndrome, the chances of having another child with Down syndrome is greatly increased. It is therfore important to know what genetic form of Down syndrome the baby has.

Can Down syndrome be diagnosed before the child is born?

All pregnant women should be offered a screening test for Down syndrome irrespective of the maternal age. Screening may be done by a maternal blood test done at 11-13 weeks (NT scan) combined with an ultrasound to look in for markers for Downs syndrome (combined first trimester sceening ). Or if the woman comes late to the Doctor then it can be a maternal blood test with the ultrasound done at 15-20 weeks. (Quadruple Test) This screening test helps identify pregnancies that are at a higher than average risk of having a baby with Down syndrome. However the test cannot diagnose Downs syndrome or birth defects. Women with abnormal screening test are offered a diagnostic test such as CVS or Amniocentesis. These tests are highly accurate at diagnosing, or more likely ruling out Down syndrome. More information please contact Indraprastha Apollo Hospitals, Sarita Vihar, Delhi Mathura Road, New Delhi – 110076
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