Down Syndrome

Down syndrome is a genetic disorder caused by an extra chromosome. It is the most common cause of intellectual disability. Down syndrome was named after the physician John Langdon Down, who published the first description of these patients in 1866. According to the Centers for Disease Control and Prevention, about 6,000 new cases of Down syndrome are identified each year in the United States. Prevalence rates of Down syndrome are reported to be 1 in 691 live births. This entry further describes Down syndrome and discusses its etiology, then looks at the health and medical concerns and issues with learning and development that are characteristic of Down syndrome.