Chromosome 18, Monosomy 18p

Important
It is possible that the main title of the report Chromosome 18, Monosomy 18p 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.

Synonyms

Short Arm 18 Deletion Syndrome
18p Deletion Syndrome
18p- Syndrome
Del(18p) Syndrome
Monosomy 18p Syndrome

Disorder Subdivisions

None

General Discussion

Chromosome 18, Monosomy 18p is a rare chromosomal disorder in which all or part of the short arm (p) of chromosome 18 is deleted (monosomic). The disorder is typically characterized by short stature, variable degrees of mental retardation, speech delays, malformations of the skull and facial (craniofacial) region, and/or additional physical abnormalities. Associated craniofacial defects may vary greatly in range and severity from case to case. However, such features commonly include an unusually small head (microcephaly); a broad, flat nose; a "carp-shaped" mouth; large, protruding ears; widely spaced eyes (ocular hypertelorism); and/or other abnormalities. Rarely (i.e., in about 10 percent of cases), Monosomy 18p may be associated with holoprosencephaly, a condition in which the forebrain (prosencephalon) fails to divide properly during embryonic development. Holoprosencephaly may result in varying degrees of mental retardation, other neurologic findings, and/or extremely variable midline facial defects, such as the presence of a single, central front tooth (maxillary incisor); closely spaced eyes (hypotelorism); an abnormal groove in the upper lip (cleft lip); incomplete closure of the roof of the mouth (cleft palate); and/or, in severe cases, absence of the nose and/or cyclopia. Cyclopia is characterized by fusion of the eye cavities (orbits) into a single cavity containing one eye.

In some individuals with Monosomy 18p, additional physical abnormalities may be present. Such findings commonly include a short, webbed neck; a broad chest with widely spaced nipples; relatively small hands and feet; and/or an unusually small penis (micropenis) and/or undescended testes (cryptorchidism) in affected males.

Monosomy 18p 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).
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Resources

Children's Craniofacial Association
13140 Coit Road
Suite 307
Dallas, TX 75240
USA
Tel: 2145709099
Fax: 2145708811
Tel: 8005353643
Email: csmith@ccakids.com
Internet: http://www.ccakids.com

Support Organization for Trisomy 18, 13, and Related Disorders
2982 South Union Street
Rochester, NY 14624-1926
Fax: (585)594-1957
Tel: (800)716-7638
Email: barbv@trisomy.org
Internet: http://www.trisomy.org

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)428-7100
Fax: (914)997-4763
Tel: (888)663-4637
Email: Askus@marchofdimes.com
Internet: http://www.marchofdimes.com

The Arc (a national organization on mental retardation)
1010 Wayne Ave
Suite 650
Silver Spring, MD 20910
Tel: (301)565-3842
Fax: (301)565-3843
Tel: (800)433-5255
TDD: (817)277-0553
Email: info@thearc.org
Internet: http://www.thearc.org/

AboutFace USA
PO Box 158
South Beloit, IL 61080
USA
Tel: 8884861209
Email: info@AboutFaceUSA.org
Internet: http://www.aboutfaceusa.org

Chromosome Deletion Outreach, Inc.
P.O. Box 724
Boca Raton, FL 33429-0724
USA
Tel: 5613954252
Fax: 5613954252
Email: info@chromodisorder.org
Internet: http://www.chromodisorder.org

Chromosome 18 Registry & Research Society
7155 Oakridge Drive
San Antonio, TX 78229
Tel: (210)657-4968
Fax: (210)657-4968
Email: office@chromosome18.org
Internet: http://www.chromosome18.org

American Heart Association
National Center
7272 Greenville Avenue
Dallas, TX 75231-4596
Tel: (214)373-6300
Fax: (214)373-0268
Tel: (800)242-8721
Email: inquire@heart.org
Internet: http://www.americanheart.org

Craniofacial Foundation of America
975 East Third Street
Chattanooga, TN 37403
Tel: (423)778-9192
Fax: (423)778-8172
Tel: (800)418-3223
Email: farmertm@erlanger.org
Internet: http://www.craniofacialcenter.com

Independent Holoprosencephaly Support Site
Web Site on the Internet

Email: hpe@att.net
Internet: http://hpe.home.att.net

Holoprosencephaly Support Group
70 Ciphook Road
Linford
Bordon
Hertfordshire, Intl GU35 0PG
United Kingdom
Tel: (01420) 473-065

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ® (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html

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 www.rarediseases.org or email orphan@rarediseases.org
Last Updated: 5/1/2003
Copyright 1989, 1990, 2001, 2003 National Organization for Rare Disorders, Inc.

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