Down syndrome (also written as Down's syndrome) is a genetic disorder caused by an extra chromossome, the chromossome 21.
The name comes from british physician John Langdom Down, who described the syndrome in 1862. In that time, when racism was considered scientific, Down conjectured that the syndrome was a de-volution (the opposite of evolution) of caucasians to inferior races, in that case, the "mongol race", and named it mongolism (hence, the word "mongoloid"). 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 (but the cases of extreme mental retardation are usually in those that were abandoned).
Other characteristics of Down syndrome are (not all of them affect an individual):
- Single transverse palmar crease
- Eyes that look like those of elves
- Smaller limbs
- Weak muscle tone
- Bigger and protuse tongue
- Congenital heart deffect
- Gastroesophageal reflux disease
- Sleep apnea
- Thyroid hormone problems
There are evidences that people with Down syndrome have higher resistence to cancer.
Down syndrome is an universal phenomemon, affecting all nationalities. It's wrong to call it "a disease", and it's not contagious.