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Down syndrome
(doun)
a congenital condition characterized by physical malformations and some degree of mental retardation. Another name for the condition is trisomy 21 syndrome, because it is concerned with a defect in chromosome 21. Specific causes are often not known. There is a relatively high incidence in children of mothers in the older childbearing
age, especially older than age 40. In a minority of cases, there may be a genetic component. Affected children show several
and sometimes all of the following physical characteristics: a small, flattened skull; a short, flat-bridged nose; wide-set
eyes with epicanthi; a protruding tongue that is furrowed and lacks a central fissure; short, broad hands; feet with a wide gap between the first
and second toes; and a little finger that curves inward. The muscles are hypotonic and there is excessive mobility of the joints; the genitalia are often underdeveloped; and congenital heart defects sometimes occur.
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