Trisomy 18

Title

Other Names:

Chromosome 18 trisomy; 18 trisomy; Edwards syndrome; Chromosome 18 trisomy; 18 trisomy; Edwards syndrome; Trisomy 16-18 (formerly); Trisomy E (formerly) See More

Categories:

Congenital and Genetic Diseases; Digestive Diseases; Eye diseases; Congenital and Genetic Diseases; Digestive Diseases; Eye diseases; Kidney and Urinary Diseases See More

Summary Summary

Trisomy 18 is a chromosome disorder characterized by having 3 copies of chromosome 18 instead of the usual 2 copies. Signs and symptoms include severe intellectual disability; low birth weight; a small, abnormally shaped head; a small jaw and mouth; clenched fists with overlapping fingers; congenital heart defects; and various abnormalities of other organs. Trisomy 18 is a life-threatening condition; many affected people die before birth or within the first month of life. Some children have survived to their teenage years, but with serious medical and developmental problems. Most cases are not inherited and occur sporadically (by chance).^[1]^[2]

Last updated: 7/7/2015

Symptoms Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms	Other Names	Learn More: HPO ID
80%-99% of people have these symptoms
Atrial septal defect	An opening in the wall separating the top two chambers of the heart	0001631
Broad forehead	Increased width of the forehead Wide forehead [ more ]	0000337
Cachexia	Wasting syndrome	0004326
Camptodactyly of finger	Permanent flexion of the finger	0100490
Cognitive impairment	Abnormality of cognition Cognitive abnormality Cognitive defects Cognitive deficits Intellectual impairment Mental impairment [ more ]	0100543
Cryptorchidism	Undescended testes Undescended testis [ more ]	0000028
Deviation of finger		0004097
Dolichocephaly	Long, narrow head Tall and narrow skull [ more ]	0000268
Global developmental delay		0001263
High forehead		0000348
Hypertelorism	Wide-set eyes Widely spaced eyes [ more ]	0000316
Hypertonia		0001276
Intrauterine growth retardation	Prenatal growth deficiency Prenatal growth retardation [ more ]	0001511
Low-set, posteriorly rotated ears		0000368
Microretrognathia		0000308
Muscular hypotonia	Low or weak muscle tone	0001252
Narrow face	Decreased breadth of face Decreased width of face [ more ]	0000275
Narrow mouth	Small mouth	0000160
Narrow palate	Narrow roof of mouth	0000189
Narrow pelvis bone		0003275
Omphalocele		0001539
Pointed helix	Spock's ear	0100810
Prominent occiput	Prominent back of the skull Prominent posterior skull [ more ]	0000269
Short nose	Decreased length of nose Shortened nose [ more ]	0003196
Short stature	Decreased body height Small stature [ more ]	0004322
Triangular face	Face with broad temples and narrow chin Triangular facial shape [ more ]	0000325
Underdeveloped supraorbital ridges		0009891
Ventricular septal defect		0001629
30%-79% of people have these symptoms
Abnormal toenail morphology	Abnormality of the toenail Abnormality of the toenails [ more ]	0008388
Abnormality of female internal genitalia		0000008
Abnormality of the fontanelles or cranial sutures		0000235
Abnormality of the hip bone	Abnormality of the hips	0003272
Anal atresia	Absent anus	0002023
Bilateral single transverse palmar creases		0007598
Blepharophimosis	Narrow opening between the eyelids	0000581
Choanal atresia	Blockage of the rear opening of the nasal cavity Obstruction of the rear opening of the nasal cavity [ more ]	0000453
Cleft palate		0000175
Congenital diaphragmatic hernia		0000776
Delayed skeletal maturation	Delayed bone maturation Delayed skeletal development [ more ]	0002750
Epicanthus	Eye folds Prominent eye folds [ more ]	0000286
Esophageal atresia		0002032
Hydronephrosis		0000126
Microcephaly	Abnormally small skull Decreased circumference of cranium Decreased size of skull Reduced head circumference Small head circumference [ more ]	0000252
Non-midline cleft lip		0100335
Oligohydramnios		0001562
Webbed neck	Neck webbing	0000465
5%-29% of people have these symptoms
Abnormality of retinal pigmentation		0007703
Abnormality of the lower limb	Lower limb deformities	0002814
Abnormality of the ribs	Rib abnormalities	0000772
Anencephaly		0002323
Aplasia/Hypoplasia of the corpus callosum		0007370
Arnold-Chiari malformation		0002308
Cataract	Clouding of the lens of the eye Cloudy lens [ more ]	0000518
Cyclopia	Cyclops eye Single central eye [ more ]	0009914
Glaucoma		0000501
Holoprosencephaly		0001360
Iris coloboma	Cat eye	0000612
Microcornea		0000482
Microphthalmia	Abnormally small eyeball	0000568
Postaxial hand polydactyly	Extra little finger Extra pinkie finger Extra pinky finger [ more ]	0001162
Spina bifida		0002414

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Do you have more information about symptoms of this disease? We want to hear from you.

Last updated: 7/2/2018

Do you have updated information on this disease? We want to hear from you.

Cause Cause

In most cases, trisomy 18 is caused by having 3 copies of chromosome 18 in each cell in the body, instead of the usual 2 copies. The extra genetic material from the 3rd copy of the chromosome disrupts development, causing the characteristic signs and symptoms of the condition.

About 5% of people with trisomy 18 have 'mosaic trisomy 18' (when there is an extra copy of the chromosome in only some of the body's cells). The severity of mosaic trisomy 18 depends on the number and locations of cells with the extra copy.

Very rarely, an extra piece of chromosome 18 is attached to another chromosome; this is called translocation trisomy 18, or partial trisomy 18. If only part of the long (q) arm of chromosome 18 is present in 3 copies, the features may be less severe than in people with full trisomy 18.^[1]

Last updated: 1/30/2012

Inheritance Inheritance

Most cases of trisomy 18 are not inherited and occur randomly due to errors in the formation of eggs or sperm. If an egg or sperm gains an extra copy of chromosome 18 during cell division and contributes to a pregnancy, the embryo will have an extra chromosome 18 (trisomy) in each cell of the body.

Mosaic trisomy 18 (when some body cells have trisomy 18 and some have a normal chromosome make-up), is also typically not inherited. Mosaic trisomy 18 is also due to an error in cell division, but the error occurs early in embryonic development. About 5% of affected people have a mosaic form of trisomy 18.

Partial trisomy 18 (when only part of chromosome 18 is present in 3 copies) can be inherited. An unaffected parent can carry a rearrangement of genetic material between chromosome 18 and another chromosome. This rearrangement is called a balanced translocation because there is no extra or missing genetic material. However, a person with a balanced translocation has an increased risk with each pregnancy to have a child with trisomy 18.^[1]

Last updated: 7/7/2015

Research Research

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

ClinicalTrials.gov lists trials that are related to Trisomy 18. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Organizations Organizations

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Chromosome 18 Registry & Research Society
7155 Oakridge Drive
San Antonio, TX 78229
Telephone: 210-657-4968
E-mail: Office@Chromosome18.org
Website: http://www.chromosome18.org/
Chromosome Disorder Outreach
PO Box 724
Boca Raton, FL 33429
Telephone: 561-395-4252
E-mail: https://chromodisorder.org/contact/
Website: http://www.chromodisorder.org
Hope For Trisomy
PO Box 921
Springtown, TX 76082
Toll-free: 866-977-6637
E-mail: info@trisomyhelp.org
Website: http://www.hopefortrisomy.org
Support Organization for Trisomy 18, 13, and Related Disorders (SOFT)
c/o Barb Vanherreweghe
2982 South Union Street
Rochester, NY 14624
Toll-free: 800-716-SOFT (7638)
Telephone: 585-594-4621
E-mail: barbsoft@rochester.rr.com
Website: http://www.trisomy.org/index.php
Trisomy 18 Foundation
4491 Cheshire Station Plaza
Suite 157
Dale City, VA 22193
E-mail: T18info@trisomy18.org
Website: http://www.trisomy18.org/site/PageServer

Do you know of an organization? We want to hear from you.

Living With Living With

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources

The Social Security Administration has included this condition in their Compassionate Allowances Initiative. This initiative speeds up the processing of disability claims for applicants with certain medical conditions that cause severe disability. More information about Compassionate Allowances and applying for Social Security disability is available online.

Learn More Learn More

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

Genetics Home Reference (GHR) contains information on Trisomy 18. This website is maintained by the National Library of Medicine.
MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
The Merck Manual for health care professionals provides information on Trisomy 18.
The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
PubMed is a searchable database of medical literature and lists journal articles that discuss Trisomy 18. Click on the link to view a sample search on this topic.

GARD Answers GARD Answers

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

My son and his wife were told the baby she carries has Edwards syndrome. Does this mean if she gets pregnant again, any future child will have this condition as well? Will she be able to have a normal child? See answer
I lost a baby to Edwards syndrome. Are my surviving children at risk for any problems as a result? See answer

Have a question? Contact a GARD Information Specialist.

References References

Trisomy 18. Genetics Home Reference. March, 2013; http://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 8/23/2015.
Haldeman-Englert C. Trisomy 18. MedlinePlus. August 2011; http://www.nlm.nih.gov/medlineplus/ency/article/001661.htm. Accessed 1/17/2012.
Trisomy 18. Genetics Home Reference (GHR). January 2009; http://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 1/17/2012.

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