Kline-felter syndrome

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Kline-felter syndrome is a genetic disorder found in males adding an extra X chromosme to the normal male karyotype. These individuals are usuallly refered to as 47,XXY males. In some cases the extra X chromosome is distrubuted unevenly throughout the body, this is refered to as mosaic Klinefelter syndrome. In even more rare cases the male with Klinefelter syndrome can have the karyotype 48, XXXY 48, XXYY or even 49, XXXXY[1]. The extra X chromosome can either come from the sperm or the egg during fertilisation or even added during the early stages of development[2].

This karyotype is usually present in only 1:500 to 1:1000 live births but is the most common sex chromosome aneuploidy in males. The phenotype of the disorder is usually only presented after maturation.

The most common symptoms of Kline-felter syndrome are sterility, hypergonadism, mild mental impairment and enlargment of the breasts[3]. Other symptoms can include delayed puberty, weak bones and a risk of certain cancers including breast and bone cancers. 


  1. Mayo Clinic Staff (2013) Klinefelter syndrome, Mayo Clinic. Klinefelter syndrome Causes - Diseases and Conditions - Mayo Clinic. Available at: http://www.mayoclinic.org/diseases-conditions/klinefelter-syndrome/basics/causes/con-20033637 (Accessed: 25 November 2014).
  2. Andrology Australia (2014) Klinefelter’s syndrome, Andrology Australia. Klinefelter’s syndrome. Available at: https://www.andrologyaustralia.org/reproductive-problems/klinefelters-syndrome/ (Accessed: 25 November 2014).
  3. [Daniel L. Hartl. (2012) Genetics: analysis of genes and genomes, 8th edition, Burlington, MA : Jones and Bartlett Learning]
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