Down syndrome (DS) is a condition in which extra genetic material causes delays in the way a child develops, and often leads to mental retardation. It affects 1 in every 800 babies born.
The symptoms of Down syndrome can vary widely from child to child. While some kids with DS need a lot of medical attention, others lead very healthy and independent lives.
Though Down syndrome can't be prevented, it can be detected before a child is born. The health problems that can go along with DS can be treated, and there are many resources within communities to help kids and their families who are living with the condition.
What are the signs and symptoms of Down syndrome?
Even though people with Down syndrome may have some physical and mental features in common, symptoms of Down syndrome can range from mild to severe. Usually, mental development and physical development are slower in people with Down syndrome than in those without the condition.
Mental retardation is a disability that causes limits on intellectual abilities and adaptive behaviors (conceptual, social, and practical skills people use to function in everyday lives). Most people with Down syndrome have IQs that fall in the mild to moderate range of mental retardation. They may have delayed language development and slow motor development.
What are the genetic changes related to Down syndrome?
Down syndrome is related to chromosome 21.
Most cases of Down syndrome result from trisomy 21, which means each cell in the body has three copies of chromosome 21 instead of the usual two copies. The extra genetic material disrupts the normal course of development, causing the characteristic features of Down syndrome. Although the connection between Down syndrome and Alzheimer disease is unclear, researchers believe that an extra copy of a particular gene on chromosome 21, the APP gene, may account for the increased risk.
A small percentage of Down syndrome cases occur when only some of the body's cells have an extra copy of chromosome 21. These cases are called mosaic Down syndrome.
Although uncommon, Down syndrome also can occur when part of chromosome 21 becomes attached (translocated) to another chromosome before or at conception. Affected people have two copies of chromosome 21, plus extra material from chromosome 21 attached to another chromosome. These cases are called translocation Down syndrome.
Some common physical signs of Down syndrome include:
There are a variety of other health conditions that are often seen in people who have Down syndrome, including:
Health Problems Are Common
Babies with Down syndrome tend to develop more slowly than other babies do. They may start walking later than other babies. About half are born with heart defects, which means there is something different with the way their hearts developed. Usually, these problems can be corrected by surgery.
Some babies also may have problems in their stomachs or a blockage in their intestines that prevents them from digesting food properly. Kids with Down syndrome are more likely to get infections that affect their lungs and breathing. When they do get infections, they often last longer. They may have eye or ear problems or digestion problems like constipation. Some may develop leukemia, a type of cancer. Each person with Down syndrome is different and may have one, several, or all of these problems.
We've mentioned a little about the features people with Down syndrome often have. In addition to the eyes and face, they may have small or misshapen ears, a large space between the big toe and the second toe, and a crease that goes across the palms of their hands. It's important to note, though, that not all people with Down syndrome look alike or have all these features.
What does a child with Down syndrome look like?
A child with Down syndrome may have eyes that slant upward and small ears that may fold over a little at the top. The child's mouth may be small, making the tongue appear large. The nose also may be small, with a flattened nasal bridge. Some babies with Down syndrome have short necks and small hands with short fingers. Having less muscle tone, they may appear somewhat? floppy?.
The child or adult with Down syndrome is often short and has unusual looseness of the joints. Most children with Down syndrome have some, but not all, of these features.