All Children's Hospital Logo

Health Information Library

Parents > A to Z > D > A to Z: Down Syndrome
A to Z: Down Syndrome

A to Z: Down Syndrome

May also be called: Trisomy 21

Down syndrome (DS) is a condition in which extra genetic material causes delays in the way a child develops, mentally and physically.

More to Know

Normally a baby inherits genetic information from its parents in the form of 46 chromosomes: 23 from each parent. In most cases of Down syndrome, a child gets an extra number 21 chromosome — for a total of 47 chromosomes. This extra genetic material is responsible for the physical features and developmental delays of Down syndrome.

It is not known why Down syndrome happens, but scientists do know that women age 35 and older have a higher risk of having a child with the condition, and the risk increases with age.

Some characteristic features of people with Down syndrome include a flat facial profile, an upward slant to the eyes, small stature, low muscle tone, and a single deep crease across the palm. Most children with DS reach developmental milestones later than other kids, but the degree to which a person is affected by DS can vary greatly.

Most, but not all, people with DS will experience other significant health problems related to Down syndrome such as congenital heart defects; respiratory, vision, and hearing problems; Alzheimer's disease; childhood leukemia; and thyroid disorders. Fortunately, many of these conditions are treatable.

Keep in Mind

People with Down syndrome have varying degrees of intellectual difficulties, but they are quite capable of developing loving relationships and have many talents to share. Medical advances also allow people with DS to live longer, fuller lives than ever before.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.

Related Articles
P    All About Genetics
T    Babysitting: Caring for Kids With Special Needs
P    Disciplining Your Child With Special Needs
P    Down Syndrome
K    Down Syndrome
P    FAQs: Prenatal Tests
P    Financial Planning for Kids With Special Needs
P    Genetic Testing
K    Kids With Special Needs
P    Sending Your Child With Special Needs to Camp
P    Support for Parents of Kids With Special Needs
K    What Is an Intellectual Disability?
P    What Is the Multiple Marker Test?
P    When Your Baby Has a Birth Defect
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995-2015 KidsHealth® All rights reserved. Images provided by iStock, Getty Images, Corbis, Veer, Science Photo Library, Science Source Images, Shutterstock, and

Additional Info

Pocket Doc Mobile App
Maps and Locations (Mobile)
Programs & Services
For Health Professionals
For Patients & Families
Contact Us
Find a Doctor

All Children's Hospital
501 6th Ave South
St. Petersburg, FL 33701
(727) 898-7451
(800) 456-4543

Use Normal Template
© 2015 All Children's Hospital - All Rights Reserved