Down syndrome occurs when a person has three (rather than two) copies of the 21st chromosome. This extra chromosome causes the characteristics associated with Down syndrome. Scientists worldwide are still working to understand how the extra chromosome 21 genes causes an individual to have Down syndrome.
Down syndrome is the most commonly occurring chromosomal condition. About one in every 800 babies is born with Down syndrome.
There are more than 350,000 people living with Down syndrome in the U.S.
Down syndrome affects people of all ages, 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 percent 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 concerns, 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.
The average life expectancy for people with Down syndrome has increased dramatically in recent decades - from 25 in 1983 to 60 today.
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 develop their full potential and lead fulfilling lives.
People with Down syndrome attend school, find work, participate in decisions that affect them, and contribute to society.