What is Down syndrome?
Down syndrome is a relatively common birth defect caused by the presence of an extra chromosome number 21 (three instead of two number 21 chromosomes, or, trisomy 21). This chromosome abnormality adversely affects both the physical and intellectual development of the individual.
What are some of the features of Down syndrome?
Down syndrome causes mental retardation, a characteristic facial appearance, and multiple malformations. It is associated with a major risk for heart malformations, a lesser risk of duodenal atresia (part of the small intestines is not developed), and a small but still significant risk of acute leukemia.
What is the nature of the chromosome abnormality?
The chromosome abnormality that causes Down syndrome is trisomy 21, an extra copy of chromosome number 21. This means that instead of having the normal 2 copies of chromosome number 21, the person with Down syndrome has 3 copies of chromosome number 21. Confirmation requires a chromosome study (analysis under the microscope of the chromosomes).
A chromosome study is also valuable to rule in or out a translocation (a type of rearrangement) of chromosome 21 that may be heritable in which case it can give rise to more cases of Down syndrome in the family. The evaluation of the Down syndrome baby and the family by a medical geneticist is often useful.
Why is it called Down syndrome?
It probably should not be, but the name has stuck. Down syndrome refers to a 19th century English physician by the name of Langdon Down. Ironically, he was not the first person to describe the condition, he added little to our knowledge of it and, in great error, he attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered obsolete. The most accurate name is probably trisomy 21.
Down syndrome is a relatively common birth defect caused by the presence of an extra chromosome number 21 (three instead of two number 21 chromosomes, or, trisomy 21). This chromosome abnormality adversely affects both the physical and intellectual development of the individual.
What are some of the features of Down syndrome?
Down syndrome causes mental retardation, a characteristic facial appearance, and multiple malformations. It is associated with a major risk for heart malformations, a lesser risk of duodenal atresia (part of the small intestines is not developed), and a small but still significant risk of acute leukemia.
What is the nature of the chromosome abnormality?
The chromosome abnormality that causes Down syndrome is trisomy 21, an extra copy of chromosome number 21. This means that instead of having the normal 2 copies of chromosome number 21, the person with Down syndrome has 3 copies of chromosome number 21. Confirmation requires a chromosome study (analysis under the microscope of the chromosomes).
A chromosome study is also valuable to rule in or out a translocation (a type of rearrangement) of chromosome 21 that may be heritable in which case it can give rise to more cases of Down syndrome in the family. The evaluation of the Down syndrome baby and the family by a medical geneticist is often useful.
Why is it called Down syndrome?
It probably should not be, but the name has stuck. Down syndrome refers to a 19th century English physician by the name of Langdon Down. Ironically, he was not the first person to describe the condition, he added little to our knowledge of it and, in great error, he attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered obsolete. The most accurate name is probably trisomy 21.
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