Down syndrome is a genetic disorder that causes physical problems and intellectual disabilities. It is most often caused by the presence of an extra copy of chromosome number 21. This condition is called Trisomy 21.
Each person born with Down syndrome is different. Some have health problems. These could include heart disease, hearing problems, or problems with their intestines. Many begin treatment for medical issues early and live full, healthy, productive lives.
There are many signs and symptoms of Down syndrome. Some people have different symptoms than others. Some have different problems at different points in their lives. Many people with Down syndrome share a distinct appearance. Common physical signs include:
- Upward, slanting eyes.
- Flattened facial features.
- Protruding tongue.
- Short neck.
- Small head, ears, and mouth.
- Broad hands with short fingers.
- Decreased muscle tone.
Because of some of these physical features, children with Down syndrome often develop at a slower rate. This includes when they learn to roll over, sit, stand, and walk. They do reach these milestones, but it takes them longer. Physical issues in areas such as the heart, brain, and GI tract can cause health problems.
In addition to physical signs, people with Down syndrome often have problems with thinking and learning. These problems include:
- Short attention span.
- Poor judgment.
- Impulsive behavior.
- Slow learning.
- Delayed language and speech.
While these kinds of problems are common, they are rarely severe.
Down syndrome is caused by a problem during cell division. This results in extra genetic material. The extra genetic material causes the features and problems of Down syndrome. There are 3 types of Down syndrome:
- Trisomy 21. In this form, the cell division issue happens during the development of the sperm or the egg. This gives the child three copies of chromosome 21 instead of the normal two copies. Up to 95% of people with Down syndrome have Trisomy 21.
- Mosaic Down syndrome. Some cells have an extra copy of chromosome 21 because of abnormal cell division in the embryo. This form is rare. Only 1% of Down syndrome cases are Mosaic.
- Translocation Down syndrome. Translocation (or shift) occurs before or at conception when part of chromosome 21 attaches onto another chromosome. It is the only form of Down syndrome that can be passed down from parent to child. This can happen even if the parent shows no symptoms of Down syndrome.
There are factors that increase your risk of having a child with Down syndrome:
- Advanced maternal age. The older the woman is, the older her eggs are. Older eggs are more likely to divide abnormally. At age 35, your risk of having a baby with Down syndrome is about 1 in 350. At age 40, the risk is 1 in 100. By age 45, your risk is 1 in 30.
- Already having a child with Down syndrome. If you have a baby with Down syndrome, you have a 1 in 100 chance of having another one.
- Being a carrier of a chromosomal abnormality. Both men and women can carry the translocation abnormality. If you are a carrier, you risk passing it on to your child.
- None of the screenings can diagnose Down syndrome. They only indicate that your risk of having a baby with Down syndrome is higher. Some women test positive in the screen but have perfectly healthy babies.
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