The National Institutes of Health (NIH) describes Down Syndrome as “a set of mental and physical symptoms that result from having an extra copy of Chromosome 21.” According to the NIH, a normal fertilized egg has 23 pairs of chromosomes. In individuals with Down Syndrome, the extra Chromosome 21 causes the body and brain to develop abnormally. Down Syndrome is also known as Trisomy 21, because of the existence of three copies of Chromosome 21 instead of two.
Characteristics of Down Syndrome. Down Syndrome falls into the category of Intellectual and Developmental Disabilities (IDD), any disability that limits intellectual ability and adaptive behaviors. Most individuals that have Down Syndrome have IQs that fall in the moderate range of IDDs. Keep in mind that Down Syndrome characteristics range from mild to severe. Those with the disorder have slower mental and physical development than those without it.
Mosaic Down Syndrome (MDS). A small percentage of those with Down Syndrome only have the extra copy of Chromosome 21 in some of the body’s cells. This is referred to as Mosaic Down Syndrome. Those with MDS may have none of the symptoms associated with Down Syndrome, all of the symptoms or some of the symptoms.
Translocation Down Syndrome (TDS). Those with TDS, instead of having three copies of Chromosome 21, have two full copies and part of a third attached to another chromosome. This disorder usually occurs in early fetal development. Those with TDS display the same symptoms as those with Down Syndrome.
Physical signs of Down Syndrome. Common physical signs of Down Syndrome, according to the NIH, include the following.
- A flat face with an upward slant to the eye
- Short neck
- Abnormally shaped ears
- A deep crease in the palm of the hand
- White spots on the iris of the eye
- Loose ligaments and poor muscle tone
- Small feet and small hands
Health risks associated with Down Syndrome. Those with Down Syndrome are more likely to also have other health complications, including the following.
- Congenital heart disease
- Intestinal problems or celiac disease
- Hearing problems
- Eye problems
- Thyroid dysfunction
- Skeletal problems
Down Syndrome currently has no cure. With early intervention, however, those with Down Syndrome can live productive lives.