Trisomy 18
Trisomy 18 is a genetic disorder in which a person has a third copy of material from chromosome 18, instead of the usual two copies.
Causes
Trisomy 18 is a somewhat common syndrome. It is three times more common in girls than boys.
The syndrome occurs when there is extra material from chromosome 18. The extra material affects normal development.
Symptoms
- Clenched hands
- Crossed legs
- Feet with a rounded bottom (rocker-bottom feet)
- Low birth weight
- Low-set ears
- Mental delay
- Poorly developed fingernails
- Small head (microcephaly)
- Small jaw (micrognathia)
- Undescended testicle
- Unusual shaped chest (pectus carinatum)
Exams and Tests
An exam during pregnancy may show an unusually large uterus and extra amniotic fluid. There may be an unusually small placenta when the baby is born.
A physical exam of the infant may show unusual fingerprint patterns. X-rays may show a short breast bone. Chromosome studies will show trisomy 18, partial trisomy, or translocation.
Other signs include:
- Hole, split, or cleft in the iris of the eye (coloboma)
- Separation between the left and right side of the abdominal muscle (diastasis recti)
- Umbilical hernia or inguinal hernia
There are often signs of congenital heart disease, such as:
- Atrial septal defect (ASD)
- Patent ductus arteriosus (PDA)
- Ventricular septal defect (VSD)
Tests may also show kidney problems, including:
- Horseshoe kidney
- Hydronephrosis
- Polycystic kidney
Treatment
Treatment of children with trisomy 18 is planned on a case-by-case basis. Which treatments are used depend on the patient's individual condition.
Support Groups
- Support Organization for Trisomy 18, 13 and Related Disorders (SOFT) - www.trisomy.org
- Trisomy 18 Foundation - www.trisomy18.org
Outlook (Prognosis)
Half of infants with this condition do not survive beyond the first week of life. Some children have survived to the teenage years, but with serious medical and developmental problems.
Possible Complications
Complications depend on the specific defects and symptoms.
When to Contact a Medical Professional
Genetic counseling can help families understand the condition, the risks of inheriting it, and how to care for the patient.
Prevention
Tests can be done during pregnancy to find out if the child has this syndrome.
Genetic testing is recommended for parents who have a child with this syndrome and who want to have more children.
Alternative Names
Edwards syndrome
Update Date: 7/8/2012
Updated by: Chad Haldeman-Englert, MD,FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2012, A.D.A.M., Inc. Duplication for commercial use must be authorized in writing by ADAM Health Solutions.
