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49, XXXXY syndrome


49, XXXXY syndrome

49, XX XXxY syndrome
Classification and external resources
ICD-9-CM 758.81
DiseasesDB 32552

49, XXXXY syndrome is an extremely rare, aneuploidic sex chromosomal abnormality; its frequency is approximately 1 out of 85,000 to 100,000 males.[1][2]


  • Pathophysiology 1
  • Effects 2
  • See also 3
  • References 4
  • External links 5


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,[3] or a variant of it.[1]

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%.[4]

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.[4]

Much like Down syndrome the mental effects of 49, XXXXY syndrome vary. Impaired speech and behavioral problems are typical.[5] 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:

See also


  1. ^ a b What is XXXXY syndrome? Retrieved March 26, 2008.
  2. ^ Visootsak J, Graham JM (2006). "Klinefelter syndrome and other sex chromosomal aneuploidies". Orphanet J Rare Dis 1: 42.  
  3. ^ 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.  
  4. ^ a b c article on 49, XXXXY syndrome. Retrieved 26 March 2008.
  5. ^ 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.  

External links

  • [1] Brain morphological abnormalities in 49,XXXXY syndrome: A pediatric magnetic resonance imaging study
  • 49,XXXXY
  • 49 XXXXY at the National Organization of Rare Diseases
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