Down syndrome is a condition in which a person has an extra chromosome, or an extra piece of one. That extra genetic material changes how a baby's body and brain develop, and it can bring both mental and physical challenges over a lifetime. People with Down syndrome may share some looks and behaviors, but each person's abilities are their own.
What causes it
Chromosomes are tiny packages inside cells that hold your genes. Genes carry DNA, the information that shapes how you look and how your body works.
People with Down syndrome have an extra copy of chromosome 21, or sometimes an extra copy of part of it. An extra copy of a chromosome is called a trisomy, which is why Down syndrome is also called trisomy 21.
It is usually not inherited. It happens by chance: an error as cells divide early in the fetus's development. Why it happens, and how many factors are involved, is not known for certain. One factor that raises the chance is the mother's age — women 35 and older are more likely to have a baby with Down syndrome.
Signs and symptoms
Symptoms differ from person to person, and the same person may face different problems at different stages of life. People with Down syndrome usually have mild to moderate intellectual disability, and development is often delayed — a child may start talking later than other children, for example.
Common physical signs include:
- a flat face and eyes that slant up
- a short neck
- small hands and feet
- poor muscle tone and loose joints
Other health problems
Many people with Down syndrome have the common physical signs and are otherwise healthy. Some have one or more birth defects or other health problems, among the more common:
- hearing loss and ear infections
- sleep apnea, in which breathing stops again and again during sleep
- eye diseases
- heart defects present at birth
- digestive problems
- problems with the upper spine
- obesity
How it is diagnosed
Down syndrome can be checked for during pregnancy or after birth. In pregnancy there are two basic kinds of test:
| Test | What it tells you |
|---|---|
| Prenatal screening | Whether the baby has a higher or lower chance of Down syndrome. A result suggesting it needs a further test to be sure |
| Prenatal diagnostic | Whether the baby has Down syndrome, by checking the chromosomes in a sample of cells. These carry a small risk of miscarriage, so they are often done only after a screening result points that way |
After birth, a provider may make a first diagnosis from the physical signs and confirm it with a karyotype test, which looks for an extra chromosome in a sample of the baby's blood.
Treatment and support
There is no single standard treatment. Care is built around each person's physical and intellectual needs, strengths and limits.
- Early in life, services aim to help children reach their full potential: speech, occupational and physical therapy, usually through each state's early intervention program.
- At school, children may need extra help or attention, though many learn in regular classes.
- Throughout life, regular medical care matters because of the birth defects and health problems that can come with Down syndrome, sometimes including extra screenings for problems that are more common in people who have it.
Sources
Based on "Down Syndrome", MedlinePlus, U.S. National Library of Medicine, drawing on the Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from medlineplus.gov
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