Down Syndrome (Trisomy 21)
Watch Video
Down syndrome (also known as trisomy 21) is a genetic disorder caused most often by a meiotic nondisjunction of chromosome 21. It may also be caused by a Robertsonian translocation--or less commonly by mosaicism. It is characterized by a number of clinical findings, such as epicanthal folds, a simian crease, brushfield spots, and more.