Health Encyclopedia



Chromosome 18 Ring

National Organization for Rare Disorders, Inc.


It is possible that the main title of the report Chromosome 18 Ring is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Ring 18
  • r 18
  • Ring Chromosome 18

Disorder Subdivisions

  • None

General Discussion

Chromosome 18 Ring is a rare disorder in which there is loss (deletion) of genetic material from one or both ends of the 18th chromosome and joining of the chromosomal ends to form a ring. Associated symptoms and findings may vary greatly in range and severity from case to case, depending upon the amount and location of lost genetic material and other factors. A ring may also be formed without the loss of any genetic material. However, many individuals with the disorder are affected by mental retardation; low muscle tone (hypotonia); growth retardation; repeated infections during the first years of life; and/or malformations of the skull and facial (craniofacial) region. Such craniofacial features often include an unusually small head (microcephaly), widely spaced eyes (ocular hypertelorism), and/or vertical skin folds that cover the eyes' inner corners (epicanthal folds). Chromosome 18 Ring is usually caused by spontaneous (de novo) errors very early in the development of the embryo that appear to occur randomly for unknown reasons (sporadically).


Children's Craniofacial Association

13140 Coit Road

Suite 517

Dallas, TX 75240


Tel: (214)570-9099

Fax: (214)570-8811

Tel: (800)535-3643



March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

Tel: (914)997-4488

Fax: (914)997-4763

Tel: (888)663-4637



The Arc

1825 K Street NW, Suite 1200

Washington, DC 20006

Tel: (202)534-3700

Fax: (202)534-3731

Tel: (800)433-5255

TDD: (817)277-0553




P.O. Box 751112

Limekiln, PA 19535


Tel: (702)769-9264

Fax: (702)341-5351

Tel: (888)486-1209



Chromosome Disorder Outreach, Inc.

P.O. Box 724

Boca Raton, FL 33429-0724


Tel: (561)395-4252

Fax: (561)395-4252



Chromosome 18 Registry & Research Society

7155 Oakridge Drive

San Antonio, TX 78229

Tel: (210)657-4968

Fax: (210)657-4968



Ear Anomalies Reconstructed: Atresia/Microtia Support Group

72 Durand Road

Maplewood, NJ 07040


Tel: (973)761-5438

Fax: (973)378-8930


NIH/National Eye Institute

31 Center Dr

MSC 2510

Bethesda, MD 20892-2510

United States

Tel: (301)496-5248

Fax: (301)402-1065



NIH/National Institute on Deafness and Other Communication Disorders

31 Center Drive, MSC 2320

Communication Avenue

Bethesda, MD 20892-3456

Tel: (301)402-0900

Fax: (301)907-8830

Tel: (800)241-1044

TDD: (800)241-1105



UNIQUE - Rare Chromosome Disorder Support Group

P.O. Box 2189


Surrey, CR3 5GN

United Kingdom

Tel: 4401883330766

Fax: 4401883330766



Craniofacial Foundation of America

975 East Third Street

Chattanooga, TN 37403

Tel: (423)778-9176

Fax: (423)778-8172

Tel: (800)418-3223



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223


For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site or email

Last Updated:  4/10/2009

Copyright  1993, 2001, 2003, 2009 National Organization for Rare Disorders, Inc.

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