49, XXXXY syndrome
|49, XX XXY syndrome|
|Classification and external resources|
As its name indicates, a person with the syndrome has one Y chromosome and four X chromosomes on the 23rd pair, thus having 49 chromosomes rather than the normal 46. As is common with aneuploidy disorders, 49, XXXXY syndrome is often accompanied by mental retardation. It can be considered a form of Klinefelter syndrome, or a variant of it.
It is genetic, but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The probability of inheriting the disease is about 1%.
The individuals with this syndrome are males, but 49, XXXXX also exists with similar characteristics as the female version.
Aneuploidy is often fatal, but in this case there is "X-inactivation" where the effect of the additional gene dosage due to the presence of extra X chromosomes is greatly reduced.
Much like Down syndrome the mental effects of 49, XXXXY syndrome vary. Impaired speech and behavioral problems are typical. Those with 49, XXXXY syndrome tend to exhibit infantile secondary sex characteristics with sterility in adulthood and have some skeletal anomalies. Skeletal anomalies include:
The effects also include:
- Cleft palate
- Club feet
- Respiratory conditions
- Short or/and broad neck
- Low birth weight
- Hyperextensible joints
- Short stature
- Narrow shoulders
- Coarse features in older age
- Epicanthal folds
- Gynecomastia (rare)
- Muscular hypotonia
- Hypoplastic genitalia
- Congenital heart defects
- A very round face in infancy
- What is XXXXY syndrome? Retrieved March 26, 2008.
- Visootsak J, Graham JM (2006). "Klinefelter syndrome and other sex chromosomal aneuploidies". Orphanet J Rare Dis 1: 42. doi:10.1186/1750-1172-1-42. PMC 1634840. PMID 1762147.
- Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. p. 179. ISBN 0-7216-0187-1.
- Webspawner.com article on 49, XXXXY syndrome. Retrieved 26 March 2008.
- Visootsak J, Rosner B, Dykens E, Tartaglia N, Graham JM (June 2007). "Behavioral phenotype of sex chromosome aneuploidies: 48,XXYY, 48,XXXY, and 49,XXXXY". Am. J. Med. Genet. A 143A (11): 1198–203. doi:10.1002/ajmg.a.31746. PMID 17497714.
-  Brain morphological abnormalities in 49,XXXXY syndrome: A pediatric magnetic resonance imaging study
- 49,XXXXY Syndrome.com
- 49 XXXXY at the National Organization of Rare Diseases