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Definition
Down syndrome commonly referred to as `Trisomy 21' is a chromosome abnormality, generally due to an extra copy of the 21st chromosome. This syndrome usually, though not always, results in mental retardation and other conditions.
What is Down syndrome?
Down syndrome is a genetic condition that causes delays in physical and intellectual development. It is one of the most common genetic birth defects, affecting approximately 1 out of every 660 births, occurring irrespective of race, religion and socio-economic status. Individuals with Down syndrome have 47 chromosomes instead of the usual 46. Chromosomes are thread like structures composed of DNA and other proteins. They are present in every cell of the body and carry the genetic information needed for a cell to develop.
Children with Down syndrome have widely recognized characteristic appearances. The head may be smaller than normal and abnormally shaped. They have prominent facial features including slanting eyes, a protruding tongue and a flattened nose. Their hands are generally short and broad with broad fingers. Retardation of growth and development is typical and most affected children never reach average adult height.
Symptoms/ Warning Signs
- Decreased muscle tone at birth
- Separated sutures (joints between the bones of the skull)
- Asymmetrical or odd shaped skull
- Round head with flat area at the back of the head
- Small skull
- Upward slanting eyes, unusual for ethnic group
- Small mouth with protruding tongue
- Broad short hands
- Single crease on palms
- Retarded growth and development
- Brushfield's Spots of the iris (an abnormality in the colored part of the eye)
Parents who have already had a baby with Down syndrome, mothers or fathers who have a re-arrangement involving chromosome 21, and mothers over 35 years of age are at greatest risk of having a baby with Down syndrome. The risk of Down syndrome increases with age, from about 1 to 1250 for a woman at age 25, to 1 - 1000 at the age 30, to 1-400 at the age 35 and 1-100 at the age 40.
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