Trisomy 18
(Edwards Syndrome)

Trisomy 18 Facts*

*Trisomy 18 facts Medically Edited by: Melissa Conrad Stöppler, MD

Trisomy 18 is a rare genetic condition that causes severe intellectual impairment and birth defects in babies who are afflicted with the disorder. Trisomy 18 is also known as Edwards syndrome.
About 1 in 5,000 newborns has trisomy 18. Approximately 80% of babies who have the condition are female.
About 90% to 95% of babies who are born with the condition will not live past one year of age.
Trisomy 18 results from having three copies of chromosome 18 instead of two.
Mosaic trisomy 18 refers to a condition in which only some cells carry an extra copy of chromosome 18.
Most cases of trisomy 18 are not inherited. Trisomy 18 often results when a random error causes a sperm or egg cell to gain an extra copy of chromosome 18.

Trisomy 18 Overview»

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Glossary

Trisomy 18 (Edwards Syndrome) Topic Guide

Definition of Trisomy 18

Trisomy 18 syndrome: There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.

SOURCE:
MedTerms.com. Trisomy 18 Syndrome.

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