Definition: a chromosomal dysgenesis syndrome consisting of a variable constellation of abnormalities caused by triplication or translocation of chromosome 21. The abnormalities include mental retardation, retarded growth, flat hypoplastic face with short nose, prominent epicanthic skin folds, small low-set ears with prominent antihelix, fissured and thickened tongue, laxness of joint ligaments, pelvic dysplasia, broad hands and feet, stubby fingers, and transverse palmar crease. Lenticular opacities and heart disease are common. The incidence of leukemia is increased and Alzheimer disease is almost inevitable by age 40 years.
Synonym(s): trisomy 21 syndrome
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