Causes of Down Syndrome Disorder

Down syndrome picture

Learn about the most common causes of Down syndrome babies including Trisomy 21, Mosaic and Translocation. The different types of Down syndrome all involve an extra copy of the chromosome 21, but each has a unique variation of which cells contain the extra copy.

This is likely the reason that physical and behavioral characteristics can vary from one child to another. There will also be a different combination of medical conditions that result from the disorder.

The three genetic causes of Down syndrome include:

  • Trisomy 21: This is the most common type of Down syndrome that you are probably most familiar with. This type accounts for more than 90 percent of cases due to there being three reproductions of chromosome 21 instead of only two that occurs in all cells. This is due to atypical cell division in the sperm or egg cell during development.
  • Mosaic: This type has only some cells with an additional chromosome 21. This assortment of normal and abnormal cells is due to irregular cell division that occurs after fertilization.
  • Translocation: This type is uncommon and occurs when only part of chromosome 21 becomes joined to another chromosome, either before or at conception. Children with this type will have the usual two copies of chromosome 21, but they also have extra material from chromosome 21 bonded to the translocated chromosome.

Despite knowing this information you may still be asking what causes down syndrome with respect to the body creating an extra chromosome 21. Currently, scientific research does not support the theory that environmental factors or the parents' activities before or during pregnancy are causes of a Down syndrome infant, but there is an increased risk with advanced maternal age.

There is also an increased risk when either a mother or father is the carrier of a translocated chromosome, which accounts for about one third of cases. The risk of this occurring is approximately 3% when fathers are the carrier and 10-15% when mothers are the carrier. However, most cases are random occurrences.

Regardless of the causes of Down Syndrome, treatment is generally the same based on whatever symptoms are displayed. For children with speech delays, a picture exchange communication system may be used as well as sign language. Parents and professionals may also find the information on my page with positive behavior supports to be helpful for behavioral problems.

Recent studies are showing that treatment based on nutritional interventions may prevent or substantially decrease typical associated symptoms. I feel this is just one more indicator that when it comes to working with children that have developmental disorders, nutrition is an extremely important aspect of treatment.

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1. Mayo Clinic Staff. (2009). Down Syndrome: Causes. 10-11-10.

2. National Down Syndrome Society. What causes down syndrome?. 3-21-11.