Down syndrome

Down syndrome, also called trisomy 21, is a genetic disorder caused by all or part of a third copy of chromosome 21. It is associated with developmental delays, mild to moderate intellectual disability, and characteristic physical features. It can be identified during pregnancy through screening and diagnostic testing, or after birth through observation and genetic testing. Education, care, and regular health screening can support quality of life.

Also known as

Trisomy 21

Cause

All or part of a third copy of chromosome 21

Common genetic form

Trisomy 21, an extra chromosome 21 in all cells