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What is Down Syndrome?

  • Down syndrome is a genetic condition that occurs when an individual has a full or partial extra copy of chromosome 21.

  • Dr John Langdon Down first identified individuals with similar traits in 1866.  In 1961 the World Health Organization recognized the genetic condition and it was named Down syndrome after Dr. Down.

  • There are three types of Down syndrome: Trisomy 21 which accounts for 95% of cases, translocation which accounts for about 4% and mosaicism accounts for about 1%.

  • Down syndrome is the most commonly occurring chromosomal condition. One in every 691 babies in the United States is born with Down syndrome and there are more than 400,000 people living with Down syndrome in the United States.

  • 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. With increases in medical treatment options, most individuals with Down syndrome live long and healthy lives.

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

  • 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.

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

  • 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.

  • For more information about medical issues relating to Down syndrome, visit

  • Additional resources:

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