Chromosome 15 Ring
National Organization for Rare Disorders, Inc.
It is possible that the main title of the report Chromosome 15 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.
Chromosome 15 Ring results from loss (deletion) of genetic material from both ends of the 15th chromosome and a joining of the ends to form a ring. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as "p" and a long arm identified by the letter "q." Chromosomes are further subdivided into bands that are numbered.
In individuals with Chromosome 15 Ring, the variability of associated symptoms and findings may depend upon the amount and location of genetic material lost from the 15th chromosome, the stability of the ring chromosome during subsequent cellular divisions, or other factors. Evidence suggests that the clinical features seen in Chromosome 15 Ring appear to result from deletions of genetic material from the long arm (q) of chromosome 15 (known as "monosomy 15q"), with the ring chromosome typically replacing a normal 15th chromosome. In addition, in some cases, only a certain percentage of an individual's cells may contain Chromosome 15 Ring, while other cells may have a normal chromosomal makeup (a finding known as "chromosomal mosaicism"), potentially affecting the variability of associated symptoms and findings.
In most cases, Chromosome 15 Ring appears to be caused by spontaneous (de novo) errors very early in embryonic development. In such cases, the parents of the affected child usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality. However, there have been rare cases in which a parent of an affected individual also has Chromosome 15 Ring. In such instances, the chances are greater of having another child with the chromosomal abnormality. In addition, a few cases have been reported in which Chromosome 15 Ring has been the result of a "balanced translocation" in one of the parents. Translocations occur when regions of certain chromosomes break off and are rearranged, resulting in shifting of genetic material and an altered set of chromosomes. If a chromosomal rearrangement is balanced, meaning that it consists of an altered but balanced set of chromosomes, it is usually harmless to the carrier. However, such a chromosomal rearrangement may be associated with an increased risk of abnormal chromosomal development in the carrier's offspring.
Chromosomal analysis and genetic counseling are typically recommended for parents of an affected child to help confirm or exclude the presence of Chromosome 15 Ring, potential mosaicism, or a balanced translocation in one of the parents.
Many individuals with Chromosome 15 Ring have some features similar to those associated with Russell-Silver syndrome (RSS), which is a genetic disorder characterized by growth deficiency and short stature, distinctive facial abnormalities, and other features. (For further information, please see the "Related Disorders" section below.) In some of these cases, genetic analysis has indicated that the prenatal and postnatal growth retardation associated with Chromosome 15 Ring (and potentially suggestive of RSS) may result from deletion of a gene known as the insulin-like growth factor I receptor (IGF1R) gene, which has been mapped to the long arm of chromosome 15 (15q25-q26).
Human Growth Foundation
997 Glen Cove Avenue
Glen Head, NY 11545
Children's Craniofacial Association
13140 Coit Road
Dallas, TX 75240
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Arc (a national organization on mental retardation)
1010 Wayne Ave
Silver Spring, MD 20910
PO Box 751112
Las Vegas, NV 89136
Chromosome Disorder Outreach, Inc.
P.O. Box 724
Boca Raton, FL 33429-0724
Little People of America, Inc.
250 El Camino Real
Tustin, CA 92780
IDEAS (IsoDicentric 15 Exchange, Advocacy and Support)
P.O. Box 674
Fayetteville, NY 13066
American Heart Association
7272 Greenville Avenue
Dallas, TX 75231-4596
UNIQUE - Rare Chromosome Disorder Support Group
P.O. Box 2189
Surrey, Intl CR3 5GN
Tel: 44 0 1883 330766
Fax: 44 0 1883 330766
Craniofacial Foundation of America
975 East Third Street
Chattanooga, TN 37403
MUMS National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
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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