Chromosome 18, Tetrasomy 18p
National Organization for Rare Disorders, Inc.
- Tetrasomy, Short Arm of Chromosome 18
Chromosome 18, Tetrasomy 18p is a very rare chromosomal disorder in which the short arm of the 18th chromosome (18p) appears four times (tetrasomy) rather than twice in cells of the body. Individuals with a normal chromosomal make-up (karyotype) have two 18th chromosomes, both of which have a short arm ("18p") and a long arm ("18q"). However, in individuals with Chromosome 18, Tetrasomy 18p, four short arms (18ps) are present in cells of the body rather than the normal two.
The symptoms of Chromosome 18, Tetrasomy 18p may vary from case to case. Many affected individuals may have abnormalities of the head and facial (craniofacial) area; malformations of the spine, hands, and/or feet; neuromuscular abnormalities, such as increased muscle tone (hypertonia), increased reflex reactions (hyperreflexia), and difficulty coordinating movement; kidney (renal) malformations; and/or additional physical abnormalities. In addition, children and adults with Chromosome 18, Tetrasomy 18p often exhibit moderate to severe mental retardation, limitations in speech, and/or behavioral abnormalities. In most cases, Chromosome 18, Tetrasomy 18p is the result of a spontaneous (de novo) genetic change (mutation) early in embryonic development that occurs for unknown reasons (sporadic).
Children's Craniofacial Association
13140 Coit Road
Dallas, TX 75240
Support Organization for Trisomy 18, 13, and Related Disorders
2982 S. Union Street
Rochester, NY 14624-1926
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
1825 K Street NW, Suite 1200
Washington, DC 20006
P.O. Box 751112
Limekiln, PA 19535
Chromosome Disorder Outreach, Inc.
P.O. Box 724
Boca Raton, FL 33429-0724
National Kidney Foundation
30 East 33rd Street
New York, NY 10016
Chromosome 18 Registry & Research Society
7155 Oakridge Drive
San Antonio, TX 78229
NIH/National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
UNIQUE - Rare Chromosome Disorder Support Group
P.O. Box 2189
Surrey, CR3 5GN
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
Tetrasomy 18p Canada
14 Deeth Drive, Unit A
Ontario, M9P 2J7
Email: Lorrine@tetrasomy18p.ca, Velvet@tetrasomy18p.ca
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Last Updated: 4/10/2009
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