Common Questions About Down syndrome
What are trisomies and what causes Down syndrome?
The term "trisomy" is used to describe the presence of three chromosomes, rather than the usual pair of chromosomes. For example, if a baby is born with three #21 chromosomes, rather than the usual pair, the baby would be said to have "trisomy 21." Trisomy 21 is also known as Down syndrome. Other examples of trisomy include trisomy 18 and trisomy 13. Again, trisomy 18 or trisomy 13 simply means there are three copies of the #18 chromosome (or of the #13 chromosome) present in each cell of the body, rather than the usual pair.
What is Down syndrome?
Down syndrome is a genetic disorder that includes a combination of birth defects, including some degree of mental retardation, characteristic facial features and, often, heart defects, visual and hearing impairment, and other health problems. The severity of all of these problems varies greatly among affected individuals. Down syndrome is one of the most common genetic birth defects, affecting approximately one in 800 to 1,000 babies. In this country, there are more than 350,000 individuals with Down syndrome, according to the National Down Syndrome Society. Life expectancy among adults with Down syndrome is about 55 years, though average lifespan varies. The name "Down syndrome" comes from the physician, Dr. Langdon Down, who first described the collection of findings in 1866. It was not until 1959 that the cause of Down syndrome (the presence of an extra #21 chromosome) was identified.
What types of problems do children with Down syndrome typically have?
• About 40 to 50 percent of babies with Down syndrome have heart defects. Some defects are
minor and may be treated with medications, while others may require surgery.
• About 10 percent of babies with Down syndrome are born with intestinal malformations that
require surgery.
• More than 50 percent have some visual or hearing impairment. Common visual problems
include crossed eyes, near- or farsightedness, and cataracts.
• Children with Down syndrome may have hearing loss due to fluid in the middle ear, a nerve
defect, or both.
•Children with Down syndrome are at increased risk of thyroid problems and leukemia. They
also tend to have many colds, as well as bronchitis and pneumonia.
• Fewer than 10 percent will have severe mental retardation.