DOWN'S SYNDROME

Definition

Down's syndrome is the most common and readily identifiable chromosomal condition associated with mental retardation. It is caused by a chromosomal abnormality: for some unexplained reason, an accident in cell development results in 47 instead of the usual 46 chromosomes. This extra chromosome changes the orderly development of the body and brain. In most cases, the diagnosis of down's syndrome is made according to results from a chromosome test administered shortly after birth.

Incidence

Approximately 4,000 children with down's syndrome are born in the U.S. each year, or about 1 in every 800 to 1,000 live births

Individuals with down's syndrome are usually smaller than their non-disabled peers, and their physical as well as intellectual development is slower.

Besides having a distinct physical appearance, children with down's syndrome frequently have specific health-related problems. A lowered resistance to infection makes these children more prone to respiratory problems. Visual problems such as crossed eyes and far- or nearsightedness are higher in those with down's syndrome, as are mild to moderate hearing loss and speech difficulty.

Approximately one third of babies born with down's syndrome have heart defects, most of which are now successfully correctable. Some individuals are born with gastrointestinal tract problems that can be surgically corrected.

Just as in the normal population there is a wide variation in mental abilities, behavior, and developmental progress in individuals with down's syndrome. Their level of retardation may range from mild to severe, with the majority functioning in the mild to moderate range. Due to these individual differences, it is impossible to predict future achievements of children with down's syndrome.