Down or Down's, Syndrome

   Down's syndrome, or Down syndrome, is a disorder caused by chromosome abnormalities that develop during germ-cell formation. If the affected ovum or sperm takes part in fertilization, the fetus will exhibit the syndrome. Characteristics include moderate to severe mental deficiency, slow physical development, stocky build, short hands, and flattened facial features.

   The syndrome was first described in 1866 by Dr. John Langdon Haydon Down (1828-1896), born in London and for many years a fellow of the Royal College of Physicians. The disorder had been called mongolism because of the Asian characteristics of eyes that appear to slant, but Down's name was later given to this disorder. In 1959 a French biologist, Jerome Lejeune, established that the production of a germ cell with an extra chromosome 21 is the most common cause of Down's syndrome.

   The possibility of this happening is more likely in the firstborn of an older mother, over forty years of age. Chromosome 21 is the smallest human chromosome, but its genes are of great importance not only in Down's syndrome but in cancer and Alzheimer's disease. People suffering from Down's syndrome may, with recent developments in medicine, live to about fifty years of age, but such individuals do not ordinarily become self-supporting. They are, nevertheless, often unusually sociable and affectionate.