Health Encyclopedia

Trisomy 18

Definition

Trisomy 18 is a genetic disorder associated with the presence of extra material from chromosome 18.

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. It is three times more common in girls than boys. The syndrome is caused by the presence of an extra material from chromosome 18. The extra material interferes with normal development.

Symptoms

Clenched hands
Crossed legs (preferred position)
Heart disease (congenital)
Hole, split, or cleft in the iris (coloboma)
Kidney problems
Low birth weight
Low-set ears
Mental deficiency
Separation between the left and right side of the rectus abdominis muscle (diastasis recti)
Small head (microcephaly)
Small jaw (micrognathia)
Umbilical hernia or inguinal hernia
Underdeveloped fingernails
Undescended testicle
Unusual shaped chest (Pectus carinatum)

Signs and tests

Examination of the pregnant woman may show an unusually large uterus and extra amniotic fluid. An unusually small placenta may be seen when the baby is born.

Physical examination of the infant may show unusual finger print patterns. X-rays may show a short breast bone. Chromosome studies show trisomy 18, partial trisomy, or translocation.

There are often signs of congenital heart disease, such as:

Tests may also show kidney problems, including:

Treatment

Medical management of children with Trisomy 18 is planned on a case-by-case basis and depends on the individual circumstances of the patient.

Support Groups

Support Organization for Trisomy 18, 13 and Related Disorders (SOFT) - www.trisomy.org
Trisomy 18 Foundation - www.trisomy18.org

Expectations (prognosis)

Fifty percent of infants with this condition do not survive beyond the first week of life. Some children have survived to teenage years, but with serious medical and developmental problems.

Complications

Complications depend on the specific defects and symptoms.

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

Prenatal diagnosis of trisomy 18 is possible with an amniocentesis or chorionic villus sampling and chromosome studies on amniotic cells. Parents who have a child with translocational trisomy 18 and want additional children should have chromosome studies, because they are at increased risk to have another child with trisomy 18.

Review Date:7/2/2007
Reviewed By:Brian Kirmse, MD, Mount Sinai School of Medicine, Department of HumanGenetics, New York, NY. Review provided by VeriMed Healthcare Network.

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