Skip Navigation

Down Syndrome: Overview

Skip sharing on social media links

Down syndrome is a set of cognitive and physical symptoms that result from having an extra chromosome 21 or an extra piece of that chromosome. It is the most common chromosomal cause of mild to moderate intellectual disabilities. People with Down syndrome also have some distinct physical features, such as a flat-looking face, and they are at risk for a number of other health conditions.

Understanding Down syndrome and other intellectual and developmental disabilities is part of the reason the NICHD was established. Today, the Institute continues to lead research on the causes, progression, treatment, and management of Down syndrome, as well as on conditions and diseases that are associated with the syndrome.

​​​ arrow pointing left For more information about this topic, select the Condition Information, Research Information, Clinical Trials, or Resources and Publications link in the menu on the left.

Common Name

  • Down syndrome

Medical or Scientific Names

  • Down syndrome
  • Trisomy 21
  • 47,XX,+21
  • 47,XY,+21
BOND National Institues of Health Home Home Division of Intramural Population Health Research