Chromosome 18p duplication

Title

Other Names:

Duplication 18p; Trisomy 18p; 18p duplication; Duplication 18p; Trisomy 18p; 18p duplication; 18p trisomy; Partial trisomy 18p See More

Categories:

Congenital and Genetic Diseases

Summary Summary

Trisomy 18p is a rare chromosomal abnormality in which there are three copies of the p arm of chromosome 18 in each cell, rather than the usual two copies. As a quick review, chromosomes are structures that hold our DNA. Our DNA contains the instructions, called genes, which tell our bodies how to develop and function. Each chromosome has a constriction, called the "centromere", at one point along its length dividing it into a shorter arm which is called the p (petite) arm and a longer arm, called the q arm. We have two copies of each chromosome, one copy inherited from our mother and the other copy from our father. Therefore, people typically have two copies of chromosome 18, one from mom and one from dad, and thus two copies of the p arm of chromosome 18. (Click here to read more about chromosomes.)

Trisomy 18p has rarely been reported. According to Mabboux et al. (2007) only 21 cases have been documented in the medical literature.^[1] The signs and symptoms vary greatly from person to person and is characterized by mental retardation, foot or hand anomalies and craniofacial anomalies. Treatment is based on the specific findings present.^[1]

Last updated: 7/16/2009

Symptoms Symptoms

According to Rodríguez (2007) et al., all the cases of trisomy 18p show a noncharacteristic facial appearance and a mental development ranging from normal to moderate impairment.^[2]

Examples of Cases:

Taylor et al. (1975) - female with no physical or mental abnormalities
Takeda et al. (1989) - female without mental retardation
Wolff et al. (1991) - mother and daughter were of normal intelligence and had a short pinky finger on both of their hands
Moog et al. (1994) - mother and son; mother had developmental delay and learning disabilities and son had moderate mental retardation and slight craniofacial anomalies
Li et al. (1998) - male with developmental delay, hypotonia (low muscle tone) and minor physical abnormalities

Some have suggested that several of the cases of trisomy 18p reported in the medical literature of people with signs and symptoms represent cases in which other chromosomal abnormalities not yet identified may explain the signs and symptoms present, suggesting that pure trisomy 18p results in little, if any, signs and symptoms.^[1]^[3] As more advanced techniques for identifying chromosomal abnormalities become available, we will learn more about the signs and symptoms associated with trisomy 18p. It is possible that some cases of trisomy 18p are being missed because they do not have any signs and symptoms and are of normal intelligence.^[1]

Last updated: 7/16/2009

Treatment Treatment

Because the presence and severity of signs and symptoms vary from person to person, treatment will also vary. It is important to work with the person's health care provider to determine the appropriate medical management plan.

Last updated: 7/16/2009

Organizations Organizations

Nonprofit support and advocacy groups bring together patients, families, medical professionals, and researchers. These groups often raise awareness, provide support, and develop patient-centered information. Many are the driving force behind research for better treatments and possible cures. They can direct people to research, resources, and services. Many groups also have experts who serve as medical advisors. Visit their website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD. Suggest an organization to add.

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: info@chromodisorder.org
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

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

The National Human Genome Research Institute, part of the National Institutes of Health (NIH), has developed a fact sheet on chromosome abnormalities, which may be helpful to you. To read this information, visit the link.

MedlinePlus, the National Library of Medicine Web site designed to direct you to information and resources that help you research your health questions, provides further information about chromosomes. Click on the link.
Genetics Home Reference (GHR) contains information on Chromosome 18p duplication. This website is maintained by the National Library of Medicine.

General Information

The National Human Genome Research Institute, part of the National Institutes of Health (NIH), has developed a fact sheet on chromosome abnormalities, which may be helpful to you. To read this information, visit the link.

MedlinePlus, the National Library of Medicine Web site designed to direct you to information and resources that help you research your health questions, provides further information about chromosomes. Click on the link.

In-Depth Information

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 Chromosome 18p duplication. 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

What are some of the signs or symptoms associated with trisomy 18p? What are some of the behavioural characteristics of this syndrome if any? What are some treatment options for an adolescent with this syndrome, ASD (autism spectrum disorder), and no intellectual disability displaying challenging behaviours? See answer

References References

Mabboux P, Brisset S, Aboura A, Pineau D, Kourbi V, Joannidis S et al. Pure and Complete Trisomy 18p Due to a Supernumerary Marker Chromosome Associated with Moderate Mental Retardation. American Journal of Medical Genetics Part A. 2007;
Rodríguez L, Liehr T, Mrasek K, Mansilla E, Martínez-Fernández ML, Garcia A, Martínez-Frías ML. Small Supernumerary Chromosome Marker Generating Complete and Pure Trisomy 18p, Characterized by Molecular Cytogenetic Techniques and Review. American Journal of Medical Genetics Part A. 2007;
Schinzel A. Catalogue of Unbalanced Chromosome Aberrations in Man. New York: Walter de Gruyter; 2001;

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