Down Syndrome
Down Syndrome is a chromosomal disorder that results in mild to severe learning disabilities and physical symptoms that include a small skull, extra folds of skin under the eyes, and a flattened nose bridge. Muscle tone throughout the body is usually low. The condition was formerly known as “mongolism” because the features of people with Down syndrome were thought to resemble those of Mongolian Asians. This term is now considered offensive and inappropriate and is no longer used.
Two other chromosomal abnormalities cause Down syndrome and occur in about 2 to 3 percent of all cases. The first, translocation, takes place when a child inherits a small, extra piece of the 21st chromosome that is attached to another chromosome. If, in addition to the translocation, two normal 21st chromosomes are also present, the person will have some of the features of Down syndrome. If there is only one normal 21st chromosome, the person will not display symptoms but the children may inherit Down syndrome. Mosaic Down syndrome results from a second type of chromosomal abnormality in which only some cells in the body have an extra chromosome.
There is no cure for Down syndrome. However, prenatal tests are available to identify fetuses with the disorder. Gynecologists recommends that the so-called triple-screen blood test be offered to all pregnant women. This test measures the levels of three chemicals in the blood of the pregnant woman to indicate the baby's risk of Down syndrome. If the risk is high, amniocentesis, a procedure for removing a sample of the amniotic fluid surrounding the fetus, is administered to confirm the findings from the blood tests. Fetal cells are present in the amniotic fluid and can be checked for the presence of the chromosomal disorder.
Two other chromosomal abnormalities cause Down syndrome and occur in about 2 to 3 percent of all cases. The first, translocation, takes place when a child inherits a small, extra piece of the 21st chromosome that is attached to another chromosome. If, in addition to the translocation, two normal 21st chromosomes are also present, the person will have some of the features of Down syndrome. If there is only one normal 21st chromosome, the person will not display symptoms but the children may inherit Down syndrome. Mosaic Down syndrome results from a second type of chromosomal abnormality in which only some cells in the body have an extra chromosome.
There is no cure for Down syndrome. However, prenatal tests are available to identify fetuses with the disorder. Gynecologists recommends that the so-called triple-screen blood test be offered to all pregnant women. This test measures the levels of three chemicals in the blood of the pregnant woman to indicate the baby's risk of Down syndrome. If the risk is high, amniocentesis, a procedure for removing a sample of the amniotic fluid surrounding the fetus, is administered to confirm the findings from the blood tests. Fetal cells are present in the amniotic fluid and can be checked for the presence of the chromosomal disorder.
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