Down syndrome
Down syndrome (also written as Down's syndrome) 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 1862. Down named the condition mongolism because the external appearance of its sufferers resembled that of the Mongolian race (one of the five racial classifications commonly used at the time). 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 are (not all of them affect every individual):
- 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 are evidences that people with Down syndrome have higher resistance to cancer.
Down syndrome is an universal phenomemon, affecting all nationalities. Although the greatest risk factor 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.
