or trisomy 21
Congenital disorder caused by an extra chromosome (trisomy) on the chromosome 21 pair.
Those with the syndrome may have broad, flat faces; up-slanted eyes, sometimes with epicanthal folds (whence its former name, mongolism); mental retardation (usually moderate); heart or kidney malformations; and abnormal fingerprint patterns. Many persons with Down syndrome can live and work independently or in a sheltered environment, but they age prematurely and have a short (55-year) life expectancy. The risk of bearing a child with the disorder increases with the mother's age; it can be detected in the fetus by amniocentesis .