What is Down syndrome?
Down syndrome affects many families every year. How Down syndrome may display in each child can depend on individual factors, including what type of Down syndrome the child has.
People with Down syndrome have an extra chromosome, or extra genes. People are generally born with 46 chromosomes, but babies born with Down syndrome will have one more.
This health condition was first accurately described by an English doctor, John Langdon Down, in 1866. Many works of art, literature, and medical records had mentioned or tried to describe the condition.
However, Down was the first person credited with pinpointing the actual condition, rather than just its characteristics. For this reason, Down is commonly known as the "father" of Down syndrome and is credited with its name.
Today, one in 700 babies in the United States are born with Down syndrome, or about 6,000 babies per year.
While this health condition can affect how your child will develop physically and mentally, children with Down syndrome can lead healthy, fulfilling lives overall.
Signs and symptoms of Down syndrome
Down syndrome is also called Trisomy 21.
This is because each person is typically born with 23 pairs of chromosomes — receiving 23 from each parent. When a child is born with Down syndrome, they have an extra copy of chromosome 21 in each cell in their body.
The extra trisomy leads to a number of effects on both physical and mental development.
Physical signs
Each child with Down syndrome will be unique, and may experience some or all of the following physical traits:
- Flat appearance of the face, particularly the nose
- Short neck
- Smaller ears
- Eyes that turn up in the corners
- Smaller hands and feet
- White spots on their eyes’ irises
- One line across the palm of their hands
- Smaller pinky fingers
- Less muscle tone
- Shorter stature, both for children and adults
- A tendency to have the tongue outside the mouth
Mental signs
If your child has Down syndrome, he or she may have troubles with speech, including being slower to speak than other children their age.
They may need help in school due to developmental issues, though many children with Down syndrome attend school within regular classes. Children with Down syndrome do have an IQ, or measure of intelligence, in the lower range.
How Down syndrome may display in each child can depend on individual factors, including what type of Down syndrome the child has.
Types of Down syndrome
There are three main types of Down syndrome: Trisomy 21, translocation, and mosaicism.
Trisomy 21
The most common type of Down syndrome, Trisomy 21 accounts for about 95% of all people with the condition. People with Trisomy 21 have three copies of chromosome 21, rather than two.
Translocation Down syndrome
People with translocation Down syndrome may have an extra full or partial copy of chromosome 21, but it is attached to another chromosome. This type is seen in about 3% of all cases.
Mosaic Down syndrome
This type accounts for about 2% of all cases of Down syndrome. A mosaic is a compilation of many things, and a person with mosaic Down syndrome will have a copy of trisomy 21 in some cells of the body, but possibly not all cells.
This means they may not display as many characteristics typical of the health condition. However, Down syndrome widely varies from person to person, so not all people with the mosaic type will necessarily see fewer symptoms.
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Causes of Down syndrome
Though most people know that Down syndrome is the result of an extra chromosome, the exact cause of the condition and what contributes to it remains unknown.
No conclusive research shows that factors before or during pregnancy, environmental factors, or genetic factors contribute to the development of Down syndrome.
Maternal age at the time of pregnancy is one factor that is linked to the presence of Down syndrome in babies. Women who get pregnant when they are 35 or older are at higher risk of having a child with Down syndrome.
Women younger than 35 account for the majority of babies. Because of this, younger women account for 80% of all pregnancies affected by this condition.
Diagnosing Down syndrome
Parents who think their child may have Down syndrome may notice the slanting eyes, flat-appearing face, or low muscle tone. Babies with Down syndrome may seem floppy in activity, and they may take longer to hit developmental milestones. These can include sitting up, crawling, or walking.
Typically, doctors will perform either a screening test or a diagnostics test to check for Down syndrome in your unborn baby.
Screening tests
A screening test can help expectant parents rule out the possibility of Down syndrome.
Previously, testing was only recommended if risk factors or a genetic history of birth defects were present. Today, doctors recommend giving the option of screening and diagnostic testing to people who are pregnant.
Diagnostic tests
While screening tests can check for Down syndrome risks, a diagnostic test can tell you whether your unborn baby actually has the condition. These tests are invasive, however, as they are performed within your uterus.
Diagnostic tests carry a small risk of miscarriage. For this reason, it is best to consult a doctor about the different tests and options you may have available.
Treatments for Down syndrome
Treatments can be far-ranging for people with Down syndrome, since the condition varies. Most sources agree that early intervention and education about the condition is key.
Babies born with Down syndrome may need immediate treatment after birth for a number of reasons. Some may be born with heart conditions, for example.
Depending on the child, they may need help with developmental abilities throughout their life. This can include help from an occupational therapist, help with regulating their diet, or help in school.
Speech therapy can help improve speaking abilities, and physical therapy helps boost muscle health and strength. Other possible therapies include emotional and behavioral therapies. Prescription medications have few documented results showing safety or how effective they are.
Because Down syndrome can lead to hearing loss or other hearing issues, assistive devices may also be useful.
In addition to treatments, parents who have a child with Down syndrome can access a number of national resources. They can also connect with other families who have members with this health condition through the Down Syndrome Registry.