MONDAY, DAY 1
WEEK 37
CHILDREN AND ADOLESCENTS
The British physician John Langdon Down (1828–1896) was a man far ahead of his time. Not only did he argue for the higher education of women, but he was also passionate about the humane treatment of the mentally handicapped. In fact, Down went on to become the medical superintendent of a mental institution in Surrey. While there, he described the physical features of a “mongoloid” disorder, which included mental retardation, flattened facial features, upward-slanting eyes, a small head, and unusually shaped ears. This condition went on to be named, in his honor, Down syndrome.
Even though Down first identified the condition in 1866, the genetic cause was not discovered until nearly a century later. In 1951, a French geneticist named Jérôme-Jean-Louis-Marie Lejeune (1926–1994) found that people with the disorder had an extra copy of chromosome 21.
Today, researchers know there are three ways for a child to wind up with that extra chromosome. In about 90 percent of Down syndrome cases, the sperm or egg cell experiences abnormal division, resulting in three copies of chromosome 21—called trisomy 21—in every cell in the body. With mosaic Down syndrome, the cells experience abnormal division after fertilization; these children have some cells with the extra chromosome 21, but not all. The last, and most uncommon, form occurs when part of chromosome 21 becomes attached to another chromosome. This form is called translocation Down syndrome.
Children with Down syndrome suffer from mental retardation, as well as a heightened risk of heart defects, leukemia, weakened immune systems, and dementia. Modern science and earlier intervention have increased the average life span of people with Down syndrome dramatically. In the early 20th century, most babies with the condition didn’t live past age 10. Today, however, people with Down syndrome frequently live to age 50 and beyond.