Down Syndrome Was Not Discovered By Dr. Down
Down syndrome (DS) is a condition due to a chromosome abnormality. The chromosome abnormality leads to impairment of both the physical and intellectual development of the individual.
In 1959, the late French physician Jerome Lejeune and coworkers reported finding an extra chromosome in each of nine children with DS. The extra chromosome in all of the children seemed to be the same-an extra copy of chromosome number 21 . Since having three instead of the normal two chromosomes of a specific type is referred to as trisomy, these children had trisomy 21, now recognized as the cause of DS.
A DS baby has certain characteristic features that may individually be quite subtle but together permit the clinical diagnosis of DS to be made at birth.
These signs of DS include:
There are many, many more minor malformations in DS.
DS is associated with major malformations, too. For example, approximately half of DS children are born with a heart defect, most often a hole between the two sides of the heart. Hirschprung's disease (congenital aganglionic megacolon) which can cause intestinal obstruction occurs more frequently in DS.
DS also carries an increased risk of acute leukemia. This risk is small in absolute terms but is still a significant added risk. The intellectual handicaps in DS are of great importance.
These handicaps may not be immediately evident, but they become increasingly apparent during infancy and early childhood as developmental delay and later in childhood and adulthood as mental retardation.
Very few adults with Down syndrome can lead independent lives because of their mental retardation. It was once thought that nearly all adults with Down syndrome developed Alzheimer's disease (dementia) so that on top of their mental handicap most people with Down syndrome were slated for premature senility. However, it now appears that a much lower proportion, perhaps 20 to 25%, of Down's adults develop dementia. The majority of adults with Down syndrome may thus be spared this fate.
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