- Down's syndrome
- a condition resulting from a genetic abnormality in which an extra chromosome is present (there are three no. 21 chromosomes instead of the usual two), giving a total of 47 chromosomes rather than the normal 46. The chances of having a Down's child are higher with increasing maternal age. Affected individuals share certain clinical features, including a characteristic flat facial appearance with slanting eyes (as in Mongolian races, which gave the former name, mongolism, to the condition), broad hands with short fingers and a single crease across the palm, malformed ears, eyes with a speckled iris (Brushfield spots), short stature, and hypotonia. Many individuals also have a degree of mental handicap, although the range of ability is wide and some individuals are of normal intelligence. Associated abnormalities, including heart defects (which affect about 40% of Down's children), intestinal malformation, deafness, and squints, may also be present.prenatal diagnosis of Down's syndrome can be obtained by amniocentesis, chorionic villus sampling, the triple marker test, and nuchal thickness scanning; the condition can be confirmed by chromosomal analysis. Down's syndrome can also occur as a result of chromosomal re-arrangement (translocation) and as part of a mosaicism. Medical name: trisomy 21.J. L. H. Down (1828-96), British physician
Medical dictionary. 2011.