Nathan+W

=**__Down's Syndrome__**=

**__About Down's Syndrome__**
Down's syndrome is an autosomal disorder. The person ends up with 47 chromosomes rather than 46. It is often caused by trisomy 21, which is when each cell in the body has three copies of chromosome 21 rather than the normal two copies. It can also be caused by an estra copy of chromosome 21 in some of the body's cells. This is known as mosiac Down's Syndrome. Down's Syndrome is associated with intellectual disability, bad muscle tone, and characteristic facial appearance. People diagnosed with DS have about a 50% chance of having a heart defect. They also have an increased chance of developing other medical conditions, as described below. DS was named after the British physician John Langdon Down.

This is a list of just some of the characteristics for people with Down's Syndrome:

 * ====Mental retardation====
 * Stunted growth
 * Atypical fingerprints
 * Separation of the abdominal muscles
 * Flexible ligaments
 * Smaller genitalia
 * Eyelid crease
 * Shortened extremities
 * Oval palate
 * Low-set and rounded ears
 * Small teeth
 * Flattened nose
 * Short neck
 * Shortened hands[[image:mccarthyscoolscience/Down_Syndrome_child.jpg width="339" height="398" align="right"]]
 * Congenital heart disease
 * Single transverse palmar crease
 * Brushfield spots

Individuals with DS have different growth parameters than typical individuals. They are often shorter, and have a smaller head circumfrence. For men with DS, the average height is 5 feet and 1 inch. As for women, the average height is 4 feet 9 iches. People with DS also have a higher risk of becoming obese as they age.

__**Life Expectancy**__
Before our generation, parents faced the sad reality that they would be burying their kids with Down's Syndrome. Nowadays, however, the typical life expectancy for kids with Down's Syndrome will surpass the death of the parents. This creates new strains on parents and support workers because now the children with Down's Syndrome must be raised without any parental assistance for some years.
 * Close to 3 quarters of babies with Down's Syndrome will die in utero (before being born).
 * About 15% of babies/infants will die before one year after birth.
 * 35% will die before age 50.
 * The last 50% will die approximately around age 55-65.

The biggest reason victims of DS die before age one is heart problems.

The second biggest leading cause of death of DS victims before age one is digestive system problems.
 * __Esophageal atresia__: When the esophagus comes to a dead end and never connects to the stomach. Therefore no food can be digested.
 * __Transesophageal fistula:__ The esophagus connects to the lungs. Some food or drink may enter the lungs.
 * __Hirschsprung disease__: There is a functional abstruction in the colon. Solid body wastes cannot be eliminated
 * __Duodenal atresia:__ A blockage of the small bowel preventing contents of the stomach from emptying out

These are all health conditions that are present at birth and are the leading causes of DS babies dying within the first year of life.

After the first year, another health concern becomes present: __Luekemia__, cancer of the blood.

IQ is another factor for an earlier death. Strauss D, Eyman carried out research in 1996 that showed the average 1 year old with Down's Syndrome that had an IQ of 45-70 (mild retardation) would live to 55. An average 1 year old with DS that had an IQ of 19 or below (profound mental retardation) would live to about 43 years.

The DS life expectancy has grown greatly in the past 40 years:
 * In 1970, the median DS life expectancy was 12 months.
 * In 2005, it had grown greatly, to 49 years.

**__Other contrubuting factors of Down's syndrome__**
====The age of the mother greatly affects the chance of Down's Syndrome. The older the mother is when she gives birth, the greater the chance of DS. Age is a contributing factor for many other forms of trisomy, such as Klinefelter Syndrome.====
 * 1 in every 1,500 babies born from a 21 year old mother will have DS.
 * For a 49 year old mother, 1 out of every 10 babies will have DS.

You can tell if your baby will have DS before they are born through amniocentesis and chorionic villus sampling. Most women should get tested if they are 35 years or older and pregnant, because age is such a big factor for trisomies.

**__References:__**

 * ====**ACOG patient education amniocentesis and chorionic villus sampling brochure.**====


 * **Gastroenterology. "Down Syndrome Life Expectancy." //History of Down Syndrome and It's Treatment//. Cdadc, 2000. Web. 06 Nov. 2011. [].**


 * **Bukatko, Danuta, and Marvin W. Daehler. "Trisomy 21 (Down Syndrome)." //Child Development: a Thematic Approach//. Boston: Houghton Mifflin, 2004. 81-82. Print.**


 * **"Down Syndrome - Genetics Home Reference." //Genetics Home Reference - Your Guide to Understanding Genetic Conditions//. U.S. National Library of Medicine, 1 Nov. 2011. Web. 06 Nov. 2011. [].**