WHAT IS DOWN SYNDROME?

Down syndrome is a genetic condition which is the most commonly occurring chromosomal condition. It occurs in 1 out of every 691 births and affects people of all races and economic levels.

Typically, babies receive 23 chromosomes from their mother and 23 from their father. A baby with Down syndrome, for unknown reasons, will have three copies of the 21st chromosome instead of two. That is why Down syndrome is also called Trisomy 21. Every cell will contain 47 instead of the typical 46 chromosomes.

There are also two other forms of Down syndrome which are quite rare – mosaic and translocation. This extra genetic material will affect a baby's development, however, the baby has also inherited many physical and personality characteristics from his/her parents as well. A definitive diagnosis can only be made with a karyotype, which is a visual display of a baby's chromosomes. In the United States there are approximately 350,000 individuals living with Down syndrome. These individuals are active, vital members of their families and communities. A life with Down syndrome is a life well worth living.

TYPES OF DOWN SYNDROME

There are three types of Down syndrome. People often can’t tell the difference between each type without looking at the chromosomes because the physical features and behaviors are similar.

Trisomy 21

About 95% of people with Down syndrome have Trisomy 21. With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.

Translocation Down syndrome

This type accounts for a small percentage of people with Down syndrome (about 3%). This occurs when an extra part or a whole extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21.

Mosaic Down syndrome:

This type affects about 2% of the people with Down syndrome. Mosaic means mixture or combination. For children with mosaic Down syndrome, some of their cells have 3 copies of chromosome 21, but other cells have the typical two copies of chromosome 21. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer features of the condition due to the presence of some (or many) cells with a typical number of chromosomes.

FACTS ABOUT DOWN SYNDROME

Information from the National Down Syndrome Society

  • Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome

  • There are three types of Down syndrome: trisomy 21 (nondisjunction) accounts for 95% of cases, translocation accounts for about 4%, and mosaicism accounts for about 1%

  • Down syndrome is the most commonly occurring chromosomal condition. Approximately one in every 700 babies in the United States is born with Down syndrome – about 6,000 each year

  • Down syndrome occurs in people of all races and economic levels

  • The incidence of births of children with Down syndrome increases with the age of the mother. But due to higher fertility rates in younger women, 80% of children with Down syndrome are born to women under 35 years of age

  • People with Down syndrome have an increased risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer’s disease, childhood leukemia and thyroid conditions. Many of these conditions are now treatable, so most people with Down syndrome lead healthy lives

  • A few of the common physical traits of Down syndrome are: low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees or not at all

  • Life expectancy for people with Down syndrome has increased dramatically in recent decades – from 25 in 1983 to 60 today

  • People with Down syndrome attend school, work, participate in decisions that affect them, have meaningful relationships, vote and contribute to society in many wonderful ways

  • All people with Down syndrome experience cognitive delays, but the effect is usually mild to moderate and is not indicative of the many strengths and talents that each individual possesses

  • Quality educational programs, a stimulating home environment, good health care and positive support from family, friends and the community enable people with Down syndrome to lead fulfilling and productive lives