Down syndrome is a combination of several birth defects that include mental retardation, characteristic facial features and other health problems.
It was named after British doctor John Langdon Down, who identified the condition in the mid-1800s.
In 1959, a professor named Jerome Lejeune discovered that the disorder is chromosomal, with patients having 47 chromosomes instead of the usual 46.
It is one of the most common genetic birth defects, affecting approximately 1 in every 1,000 births, and approximately 350,000 Americans have Down syndrome.
Between 40 and 50 percent of Down syndrome patients are born with heart problems, and more than half will have some form of hearing or visual deficiency.
Patients also have an increased risk of leukemia, thyroid disorders and pneumonia.
What Causes It?
The presence of a third copy of chromosome 21 - called Trisomy 21 - is what causes 95 percent of Down syndrome, though exactly how this occurs is unknown.
Statistically, the risk of having a child with Down syndrome increases with the mother's age, from 1 in 1,250 for women age 25 to roughly 1 in 100 at age 40.
Since it is a genetic disorder, there is no cure for Down syndrome, and there are also no known preventative measures. Some recent studies suggest that pregnant women who take vitamins containing folic acid may reduce the risk of having a child with Down syndrome, but this has not yet been confirmed.
Prenatal testing using amniocentesis can diagnose Down syndrome during pregnancy, but is not usually performed unless the mother has a high risk of having a baby with birth defects. Ultrasound can also detect many cases of Down syndrome.
Life with Downs Syndrome
Since the level of developmental retardation varies widely, with most falling in the mild to moderate range, children with Down syndrome can do many of the things any child can do.
Early intervention and other special programs begin during preschool years to help children develop skills, and many higher-functioning students can be integrated into regular classrooms.
Many with the disorder grow to hold regular jobs and an increasing number of adults live in semi-independent communities or on their own.
People with Down syndrome form friendships, go to work, laugh and marry... just like everyone else.
The life expectancy of someone with Down syndrome in the U.S. is roughly 55 years.
