I once had a set of twins coming to my clinic. One twin was developing normally, and the other twin had Down Syndrome and then developed Autism at the age of four four. Recent studies find that 7 to 10 percent of children with Down Syndrome also have Autism.
In 1959 the genetic basis of Down Syndrome was found to be trisomy 21 in 95 percent of the cases and the extra chromosome is usually maternal in origin. People with Down Syndrome are depicted in ancient art; so apparently the disorder has been around for a long time. In 1866 Dr. John Langdon Down wrote about the facial similarities of many of his patients with mental retardation using a racial description (Mongol), which unfortunately stayed around for nearly a century. Once the genetic basis of the disorder was known,the terminology changed and now the correct terminology is to refer to them as persons with trisomy 21 or a person with Down Syndrome. See http://www.nas.com/downsyn/trumble.html for a detailed discussion of Down Syndrome.
Women older than forty or mothers who already have a child with Down Syndrome are more likely to give birth to babies with Down Syndrome, and routinely undergo amniocentesis at sixteen weeks. Taking into account surgical and spontaneous abortions the incidence of Down’s is approximately one in every eight hundred births. Younger mothers who do not undergo amniocentesis deliver the majority of Down’s babies because they don’t get tested. A new test, which combines blood tests and an ultrasound, is 90 percent accurate in the first trimester and can be done four to six weeks earlier than the standard Triple Test.
Why some children with Down Syndrome develop autism and other do not is not known.
See Case History # 15 in Little Bubba's Not Ready for Nashville Yet at http://www.aba4autism.com
