What Causes Down syndrome?
It has been known for some time that the risk of having a child with Down syndrome increases with advancing age of the mother; i.e., the older the mother, the greater the possibility that she may have a child with Down syndrome. However, most babies with Down syndrome (more than 85 percent) are born to mothers younger than 35 years. It is well known that the extra chromosome in trisomy 21 could either originate in the mother or the father. Most often, however, the extra chromosome comes from the mother.
What are the Different Types of Down syndrome?
The vast majority of children with Down syndrome (approximately 95 percent) have an extra 21 chromosome. Instead of the normal number of 46 chromosomes in each cell, the individual with Down syndrome has 47 chromosomes. This condition is called trisomy 21.
The second type is called translocation since the extra 21 chromosome is attached or translocated on to another chromosome, usually on chromosome 14, 21 or 22. If translocation is found in a child with Down syndrome, it is important to examine the parents’ chromosomes, since in at least one-third of the cases, a parent may be a carrier of the translocation. This form of chromosome error is found in three to four percent of the individuals with Down syndrome.
Another chromosome problem, called mosaicism, is noted in about one percent of individuals with Down syndrome. In this case, some cells have 47 chromosomes and others have 46 chromosomes. Mosaicism is thought to be the result of an error in cell division soon after conception.
How Do Children with Down syndrome Develop?
Children with Down syndrome are usually smaller, and their physical and mental developments are slower than youngsters who do not have Down syndrome. The majority of children with Down syndrome experience a mild to moderate range of cognitive delays. However, some children have very minimal cognitive delays; they may function in the borderline to low average range; others may be severely cognitively delayed. There is a wide variation in mental abilities and developmental progress in children with Down syndrome. Also, their motor development is slow; and instead of walking by 12 to 14 months as other children do, children with Down syndrome usually learn to walk between 15 to 36 months. Language development is also markedly delayed. It is important to note that a caring and enriching home environment, early intervention and integrated education efforts will have a positive influence on the child’s development.
What kind of information can be provided through genetic counseling?
Parents who have a child with Down syndrome have an increased risk of having another child with Down syndrome in future pregnancies. It is estimated that the risk of having another child with Down syndrome is about one in 100 in trisomy 21 and mosaicism. If, however, the child has translocation Down syndrome and if one of the parents is a translocation carrier, then the risk of recurrence increases markedly. The actual risk depends on the type of translocation and whether the translocation is carried by the father or the mother.
What health concerns are often observed in people with Down syndrome?
The child with Down syndrome is in need of the same kind of medical care as any other child. The pediatrician or family physician should provide general health maintenance, immunizations, attend to medical emergencies and offer support and counseling to the family. There are, however, situations when children with Down syndrome need special attention.
60-80% percent of children with Down syndrome have hearing deficits. Therefore, audiologic assessments at an early age and follow-up hearing tests are indicated. If there is a significant hearing loss, the child should be seen by an ear, nose and throat specialist.
Forty to 45% of children with Down syndrome have congenital heart disease. Many of these children will have to undergo cardiac surgery and often will need long term care by a pediatric cardiologist.
Intestinal abnormalities also occur at a higher frequency in children with Down syndrome. For example, a blockage of the food pipe (esophagus), small bowel (duodenum) and at the anus are not uncommon in infants with Down syndrome. These may need to be surgically corrected at once in order to have a normal functioning intestinal tract.
Children with Down syndrome often have more eye problems than other children who do not have this chromosome disorder. For example, three percent of infants with Down syndrome have cataracts. They need to be removed surgically. Other eye problems such as cross-eye (strabismus), near-sightedness, far-sightedness and other eye conditions are frequently observed in children with Down syndrome.
Another concern relates to nutritional aspects. Some children with Down syndrome, in particular those with severe heart disease, often fail to thrive in infancy. On the other hand, obesity is often noted during adolescence and early adulthood. These conditions can be prevented by providing appropriate nutritional counseling and anticipatory dietary guidance.
Down Syndrome Guild of Greater Kansas City
5960 Dearborn Street, Suite 100
Mission, KS 66202
Down syndrome is the most commonly occurring genetic condition at 1 in every 800 births. Down syndrome occurs in people of all races and economic levels. More than 250,000 people in the United States are living with the condition. DSG welcomes approximately 50 new babies each year. Down syndrome is not a disease and people do not suffer from it. They are born with Down syndrome and will have it their whole life. They cannot give it to someone else and they cannot be cured of it.
Common physical traits of Down syndrome include low muscle tone, small stature, almond shaped eyes, and a single deep crease across the center of the palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees or not at all.
People with Down syndrome have an increased risk for certain medical conditions such as congenital heart defects, gastrointestinal issues, respiratory difficulty, hearing and vision problems, Alzheimer's disease, childhood leukemia, and thyroid conditions. However, many of these conditions are now treatable, so most people with Down syndrome lead healthy lives. Life expectancy for people with Down syndrome has increased dramatically in recent decades - from 25 in 1983 to 60 today.
People with Down syndrome experience cognitive delays in the mild to moderate range. It’s important to remember that IQ is not indicative of the many strengths and talents that each individual possesses. Individuals with Down syndrome are achieving at levels we never once thought possible.
Quality educational programs, a stimulating home environment, good health care, and positive support from family, friends and the community enable people with Down syndrome to develop their full potential and lead fulfilling lives. People with Down syndrome are attending college, marrying and working competitively in their communities in increasing numbers.
Myths & Truths
There are a lot of misconcpetions regarding Down syndrome. DSG strives to provide accurate and up to date information to help debunk outdated myths and stereotypes that exist.
Did you know?
People with Down syndrome...
- Are living in their communities with some support
- Are often fully included in school with their typical peers
- Are going to college more frequently
- Are employed as artists, actors, child care workers
- Enjoy healthy relationships and some get married
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