Abstract
Down syndrome, also called Down’s syndrome (DS), is the most common chromosomal condition associated with intellectual disability and is characterized by a variety of additional clinical findings. It occurs in approximately 1 of 800 births worldwide. In the United States, DS accounts for approximately 500 live births annually, and more than 200,000 persons are living with the disorder. The original description of the syndrome, in 1866, has been attributed to John Langdon Down, a physician from Cornwall, England. More than 90 years later, the chromosomal cause was delineated and the condition was named Down syndrome.
The potential for the development and socialization of persons with DS has been increasingly realized, and early support for affected children and their families is widely implemented, although disparity in access to health care and other supportive resources still exists. There is considerable phenotypic variation among patients, and intellectual disability is more commonly moderate but ranges from mild to severe, whereas social function is often high relative to the cognitive impairment. There are also differences in the incidence and presentation of DS according to ethnic background and geographic region.
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