|Down's syndrome or (US) Down syndrome|
|a. pathol Former name: mongolism, Technical name: trisomy 21 a condition caused by the presence of an extra copy of chromosome 21 resulting in learning difficulties and physical differences, such as shorter stature|
|b. (as modifier): a Down's syndrome baby|
|Down syndrome or (US) Down syndrome|
|Down syndrome (doun) or Down's Syndrome (doun) Pronunciation Key
A congenital disorder caused by the presence of an extra 21st chromosome. People with down syndrome have mild to moderate mental retardation, short stature, and a flattened facial profile. The syndrome is named after its discoverer, British physician John Langdon Haydon Down (1828-1896).