What Is Down Syndrome?
Down syndrome is a genetic condition that causes mild to serious physical and developmental problems.
People with Down syndrome are born with an extra chromosome. Chromosomes are bundles of genes, and your body relies on having just the right number of them. With Down syndrome, this extra chromosome leads to a range of issues that affect you both mentally and physically.
Down syndrome is a lifelong condition. Although it can’t be cured, doctors know more about it now than ever. If your child has it, getting the right care early on can make a big difference in helping them live a full and meaningful life.
Each person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe. Some people are healthy while others have significant health problems such as serious heart defects.
Children and adults with Down syndrome have distinct facial features. Though not all people with Down syndrome have the same features, some of the more common features include:
- Flattened face
- Small head
- Short neck
- Protruding tongue
- Upward slanting eye lids (palpebral fissures)
- Unusually shaped or small ears
- Poor muscle tone
- Broad, short hands with a single crease in the palm
- Relatively short fingers and small hands and feet
- Excessive flexibility
- Tiny white spots on the colored part (iris) of the eye called Brushfield’s spots
- Short height
Infants with Down syndrome may be average size, but typically they grow slowly and remain shorter than other children the same age.
Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.
Types of Down Syndrome
There are three types of Down syndrome:
- Trisomy 21. This is by far the most common type, where every cell in the body has three copies of chromosome 21 instead of two.
- Translocation Down syndrome. In this type, each cell has part of an extra chromosome 21, or an entirely extra one. But it’s attached to another chromosome instead of being on its own.
- Mosaic Down syndrome. This is the rarest type, where only some cells have an extra chromosome 21.
You can’t tell what type of Down syndrome someone has just by how they look. The effects of all three types are very similar, but someone with mosaic Down syndrome may not have as many symptoms because fewer cells have the extra chromosome.
Down Syndrome Diagnosis
A doctor may suspect Down syndrome in a newborn based on the baby’s appearance. That can be confirmed by a blood test called a karyotype test that lines up the chromosomes and will show if there’s an extra chromosome 21.
Down Syndrome Screening in Pregnancy
Routine tests done during pregnancy can check if it’s likely your baby has Down syndrome. If those results are positive, or if you’re at high risk, you may choose to have additional, more invasive tests to be certain.
In the first trimester, you may have:
- Blood tests. Your doctor will measure the levels of a protein called PAPP-A and a hormone called hCG in your blood. Anything out of the normal range could mean a problem with the baby. If you’re at high risk for Down syndrome, they may also look for DNA from the baby in your blood, which they can examine for chromosome abnormalities.
- Ultrasound. Your doctor will look at a picture of your baby and measure the folds of tissue at the back of their neck. Babies with Down syndrome tend to have extra fluid there.
In the second trimester, you may have:
- Blood tests. Either a triple or quad-screen test measures other substances in your blood, including the protein AFP and the hormone estriol. Those levels, combined with the results from the first trimester tests, give your doctor a good estimate of the chances your baby has Down syndrome.
- Ultrasound. When your baby is more developed, an enhanced ultrasound can show some of the physical features of Down syndrome.
Other kinds of tests can diagnose Down syndrome before your baby is born by checking a sample of their DNA for an extra chromosome 21:
- Chorionic villus sampling (CVS). This can be done during the first trimester, using cells taken from the placenta.
- Amniocentesis. Fluid is taken from the amniotic sac surrounding the baby, usually during the second trimester.
- Percutaneous umbilical blood sampling (PUBS). This is also done in the second trimester using blood removed from the umbilical cord.
Down Syndrome Treatments
There’s no specific treatment for Down syndrome. But there is a wide range of physical and developmental therapies designed to help people with Down syndrome reach their full potential. The earlier you start them, the better. Each child will have different needs. Yours may benefit from:
- Physical, occupational, and speech therapy
- Specialized education services
- Social and recreation activities
- Programs that offer job training and teach self-care skills
You’ll also work closely with your child’s doctor to watch for and manage any health problems associated with the condition.
When to see a doctor
Children with Down syndrome usually are diagnosed before or at birth. However, if you have any questions regarding your pregnancy or your child’s growth and development, talk with your doctor.