- A form of mental retardation generally caused by an extra chromosome. The
child's IQ is usually less than 50 and his or her physical characteristics are
distinctive, most notably slanted eyes.
- A common form of mental retardation caused by a
chromosomal abnormality; formerly called mongolism. Two types are
recognized, based on the nature of the chromosomal aberration: the translocation
type and the nondisjunction type. Physical findings include widely spaced
eyes with slanting openings, small head with flattened occiput, lax joints,
flabby hands, small ears, and congenitial anomalies of the heart.
Source: Edgerton, Jane E. 1994. American Psychiatric Glossary, 7th Edition.
Washington, DC: American Psychiatric Press
See also chromosome 21.