Down’s Syndrome is a type of mental retardation caused by an extra chromosome, resulting in a moderate to severe level of general retardation. Measurable intelligence quotients could range from 20 to 55.
First described by J. Langdon-Down in 1866, this syndrome was initially called mongolism due to the resemblance in facial appearance to members of the Mongolian race. Later it was discovered that the syndrome is caused by an extra chromosome (no. 21) which triples instead of pairing. Known as trisomy 21, or Down’s syndrome after the discoverer, this leaves 47 chromosomes instead of the normal 46. While we know that this extra chromosome is responsible for Down’s syndrome, we do not yet know how it has its effect.
This widely known, common form of retardation is the result of cell division and is not inherited. Either parent may contribute the chromosome. It is known that the occurrence of this syndrome increases from about 1 in every 1,000 births to mothers age 20 years, to 25 per 1,000 births for women age 35, to about 88 per 1,000 births to mothers age 49.
It is not clear why the mother’s age is associated with the syndrome. It is possible that the mother’s eggs, which are all present at her birth, have been exposed to more environmental agents or stresses. Perhaps hormonal changes in midlife influence the process.
There is little evidence to show that the father’s age is involved. If so, it is not significant until the father is in the mid-fifties.
Down’s syndrome is characterized by almond-shaped eyes that slant upward, a small nose with a low bridge, and a furrowed tongue that protrudes because the mouth is small and has a low roof. The head may be flattened in the back. The ears are small and sometimes the tops are folded a little. The nose is also flattened and wide. The child is often short. These children are often born with heart problems, a susceptibility to colds and pneumonia, and more susceptibility to Alzheimer’s disease as they age. Less than 60% of Down’s syndrome children live more than 5 years after birth. The approximate life span of the remainder is 35 to 40 years.
Down’s syndrome children are usually good-natured, happy, affectionate, socially well adjusted, and playful. They can usually do most things that any young child can do, such as walking, talking, dressing themselves, and being toilet trained. However, they do these things a little later than other children. Considerable care is necessary for many of these individuals. While some are capable of learning normal skills to contribute in various jobs and some marry, most are too retarded to live alone responsibly.