What Is Down Syndrome? Its Causes, Effects And Prevention

Down syndrome can be described as a genetic disorder, which usually leads to mental retardation and development delays in kids. This condition usually becomes evident to parents and doctors soon after the child is born. Though children that are born with this genetic disorder may be close to their normal height and weight, they tend to be much smaller than the other kids when they begin to grow. With age, there are many other physical, mental and behavioral characteristics of this disorder that also become evident.
Down syndrome can be classified into three different types, Standard or Non-disjunction Down syndrome, Translocation Down Syndrome and Mosaic Down Syndrome.

Of the three types, Mosaicism is the least common, as it is responsible for only 1% to 2% of all the Down syndrome instances.

What Causes Mosaic Down Syndrome?

Our cells have 23 pairs of chromosomes; normally, in all the pairs, one chromosome comes from the father and the other one comes from the mother. Down syndrome occurs in case there is an abnormal division of cells in chromosome 21, the chromosome that is instrumental in the development of this disorder.

In about 90% of the instances, the disorder occurs due to Trisomy 21, where a child has 3 copies of the 21st chromosome in all the cells, instead of two. This type of Down syndrome usually occurs because of abnormal division of cells at the time of egg cell or sperm cell development.

At times, a part of the 21st chromosome gets attached to another chromosome, prior to or at the time of conception. When this happens, the child suffers from Translocation Down Syndrome. Children who have this form of Down syndrome normally have two pairs of chromosome 21. However, they also generally have some extra material from the 21st chromosome attached on the trans-located chromosome. Translocation Down syndrome isn’t very common and constitutes for about 2% to 3% of all Down syndrome cases.

Mosaic Down syndrome is the rarest variation of the disorder and it occurs when a child has some cells with an extra copy of chromosome 21; however, some cells have the normal two copies of chromosome 21. This mosaic of abnormal and normal cells takes places because of abnormal cell division after fertilization. Only about 1% to 2% of all Down syndrome instances are caused by Mosaic Down syndrome.

Effects Of Mosaic Down Syndrome

Children who have Down syndrome usually suffer from several different complications. Some of the possible Down syndrome effects include:

  • Dementia and seizures during the later part of life (before the age of 40).
  • Early menopause (in women).
  • Gastrointestinal blockage.
  • Hearing loss.
  • Infectious diseases like pneumonia, because of poor immunity.
  • Leukemia.
  • Life-threatening heart defects that may require surgery in early infancy.
  • Obesity.
  • Poor vision.
  • Premature aging.
  • Sleep apnea due to soft tissue and skeletal alterations that block the airways.
  • Thyroid problems.

Can Down Syndrome Be Prevented?

Unfortunately, there is no definite way for the prevention of Down syndrome, though people who are at the risk of bearing a child with this disorder should take the advice of a genetic counselor at the time of planning a baby. This also applies to parents who already have a child having Down syndrome.

A genetic counselor will not be able to prevent Down syndrome either, but can help explain the tests available to check for this disorder. It is also important for parents to understand pros and cons of these tests, before deciding to go in for them.

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