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Syndactyly
Syndactyly

Trisomy 18
Definition:
Trisomy 18 is a syndrome associated with the presence of a third (extra) number 18 chromosome.

Alternative Names:
Edwards syndrome

Causes, incidence, and risk factors:
Trisomy 18 is a relatively common syndrome affecting approximately 1 out of 3,000 live births and affecting girls more than three times as often as boys. Multiple abnormalities are associated with the presence of an extra number 18 chromosome, many which are not compatible with more than a few months of life. Few infants survive beyond the first year.

Common findings include low birth weight, mental retardation, low-set ears, malformed ears, small jaw (micrognathia), hand abnormalities, congenital heart disease, hernias, and cryptorchidism. There may be many other abnormalities noted.
Symptoms:
Signs and tests:

Examination of the pregnant woman may show polyhydramnios (extra amniotic fluid). At the birth of the child, an unusually small placenta may be noted.

Physical examination may show an excess of arched type finger print patterns. X-rays may reveal a short breast bone (sternum). Chromosome studies show trisomy 18, partial trisomy, or translocation.
Treatment:
Treatment is supportive, but life-sustaining measures are not recommended.
Support Groups:
Support Organization for Trisomy 18, 13 and Related Disorders (SOFT)
2982 S Union St
Rochester, NY 14624
Phone: 716-594-4621
Toll-Free: 1-800-716-7638
Website: http://www.trisomy.org/http://www.trisomy.org
Expectations (prognosis):
The abnormalities of trisomy 18 are generally not compatible with more than a few months of life. Fifty percent of the affected infants do not survive beyond the first week of life. More than 10 children have survived to teenage years, but usually with marked handicaps.
Complications:
Complications depend on the specific abnormalities that affect the infant.
Calling your health care provider:
Call your health care provider and genetic counselor if you have had a child with Trisomy 18 and you plan to have another child.
Prevention:
Intrauterine diagnosis of trisomy 18 is possible with an amniocentesis and chromosome studies on amniotic cells. Parents who have a child with translocational trisomy 18 should have chromosome studies, because they are at increased risk for another child with trisomy 18.
Review Date: 11/4/2001
Reviewed By: David G. Brooks, M.D., Ph.D., Division of Medical Genetics, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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