Down syndrome
Down syndrome (also written as Down's syndrome, technical name Trisomy 21[1]) is a genetic disorder caused by an extra copy of chromosome 21. The greatest risk factor for having a child with Down syndrome is increased maternal (and, to a lesser extent, paternal) age.
The name comes from British physician John Langdom Down, who described the syndrome in his 1862 paper, "Observations on an Ethnic Classification of Idiots". Down conjectured that the syndrome was a "degeneracy" of caucasians to mongols (the mongolian race was one of the five racial classifications commonly used at the time), and the term mongolism was inpired by his paper. Currently, the terms "mongolism" and "mongoloid" are considered offensive.
The most important medical aspect of Down syndrome is mental retardation. Individuals with Down syndrome have mild to severe mental retardation. It is impossible to reliably predict what the eventual level of function of a child with Down syndrome will be.
Other characteristics of Down syndrome (not all of which affect every individual who has Down's) are :
- Single transverse palmar crease
- Epicanthic folds and oblique eye opening
- Smaller limbs
- Weak muscle tone
- Enlarged, protruding tongue
- Congenital heart defect
- Gastroesophageal reflux disease
- Otitis and hearing deficits
- Sleep apnea
- Thyroid hormone problems
- Leukemia
- Early onset Alzheimer's disease
There is some evidence that people with Down syndrome are at higher risk than others of developing leukemia, but lower risk of developing other cancers[2].
The greatest risk factor in is increased maternal age, the majority of children with Down syndrome are born to mothers under the age of 35, because the vast majority of children as a whole are born to younger mothers.
