Down Syndrome

Also known as: Trisomy 21

What is Down Syndrome?

Normally all cells in the body have 23 pairs of rod-like structures called chromosomes which carry the genetic material (genes) we get from our parents and which control how we look, how we grow and how we will function physically, emotionally and intellectually, etc.

Chromosomal and genetic abnormalities can change all or some of these characteristics. Down syndrome babies/children and adults all have an extra full or partial piece of chromosome 21. It is the commonest chromosomal disorder in the USA.

What causes Down syndrome?

There are 3 types of Down syndrome which result from different mechanisms, all of which result in an extra piece of chromosome 21 in some or all of their cells. While the exact cause is unknown, a mother's age (older than 35 years), and/or there being a sibling with Down syndrome seems to increase the chances for a Down syndrome baby.

What are the signs/symptoms of Down syndrome?

Babies with Down syndrome are usually diagnosed at birth by the presence of a number of physical signs. These include:

• Poor muscle tone
• A single crease across the palm of the hand
• A short neck
• Flat face
• Upward slant of the eyes

They also have a variable degree of intellectual disability. Down syndrome babies frequently have other abnormalities like heart, intestine, ear or lung problems.

What are Down syndrome care options?

While there is no cure for Down syndrome, parents and their pediatrician along with the appropriate specialists, will have a management plan to treat any other physical abnormality, minimize any potential complication and to optimize the physical, intellectual and emotional well-being of the child with a special education program and help with learning, speech, nutrition and movement.

Reviewed by: Parul B Jayakar, MD

This page was last updated on: September 16, 2025 12:20 PM