Klinefelter's syndrome

Klinefelter's syndrome
Classification and external resources

47,XXY
ICD-10 Q98.0-Q98.4
ICD-9 758.7
eMedicine ped/1252
MeSH D007713

Klinefelter syndrome, 46/47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome.[1] Because of the extra chromosome, individuals with the condition are usually referred to as "XXY Males", or "47, XXY Males".[2]

In humans, Klinefelter syndrome is the most common sex chromosome disorder in males[3] and the second most common condition caused by the presence of extra chromosomes. The condition exists in roughly 1 out of every 500-650 males[4][5] but many of these people may not show symptoms. Other mammals also have the XXY syndrome, including mice.[6]

Principal effects include hypogonadism and reduced fertility. A variety of other physical and behavioural differences and problems are common, though severity varies and many boys and men with the condition have few detectable symptoms.

The syndrome was named after Dr. Harry Klinefelter, who in 1942 worked with Fuller Albright at Massachusetts General Hospital in Boston, Massachusetts and first described it in the same year.[7]

Contents

Signs and symptoms

Affected males are sometimes infertile, or may have reduced fertility. Advanced reproductive assistance is sometimes possible.[8] Some degree of language learning or reading impairment may be present,[9] and neuropsychological testing often reveals deficits in executive functions, although these deficits can often be successfully ameliorated through early intervention.[10][4] There may also be delays in motor development which can be addressed through occupational therapy.[11] In adults, possible characteristics vary widely and include little to no signs of affectedness, a lanky, youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue).[12] Gynecomastia is present to some extent in about a third of affected individuals, a slightly higher percentage than in the XY population. About 10% of XXY males have gynecomastia noticeable enough that they may choose to have cosmetic surgery.[13]

The term hypogonadism in XXY symptoms is often misinterpreted to mean "small testicles" or "small penis". In fact, it means decreased testicular hormone/endocrine function. Because of this (primary) hypogonadism, individuals will often have a low serum testosterone level but high serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels.[14] Despite this misunderstanding of the term, however, it is true that XXY men may also have microorchidism (i.e. small testicles).[14]

The more severe end of the spectrum of symptom expression is also associated with an increased risk of germ cell tumors, male breast cancer,[15] and osteoporosis,[5] risks shared to varying degrees[16] with females. In contrast to these potentially increased risks, it is currently thought that rare X-linked recessive conditions occur less frequently in XXY males than in normal XY males, since these conditions are transmitted by genes on the X chromosome, and people with two X chromosomes are typically only carriers rather than affected by these X-linked recessive conditions.

There are many variances within the XXY population, just as in the most common 46,XY population. While it is possible to characterise 47,XXY males with certain body types, that in itself should not be the method of identification as to whether or not someone has 47,XXY. The only reliable method of identification is karyotype testing.

Diagnosis

A karyotype is used to confirm the diagnosis. In this procedure, a small blood sample is drawn. White blood cells are then separated from the sample, mixed with tissue culture medium, incubated, and checked for chromosomal abnormalities, such as an extra X chromosome.

Diagnosis can also be made prenatally via chorionic villus sampling or amniocentesis, tests in which fetal tissue is extracted and the fetal DNA is examined for genetic abnormalities. A 2002 literature review of elective abortion rates found that approximately 58% of pregnancies in the United States with a diagnosis of Klinefelter syndrome were terminated.[17]

Cause

The extra X chromosome is retained because of a nondisjunction event during meiosis I (gametogenesis). Nondisjunction occurs when homologous chromosomes, in the case the X and Y sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome. Fertilizing a normal (X) egg produces an XXY offspring. The XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in about 1 in 500 live male births.[5]

Another mechanism for retaining the extra X chromosome is through a nondisjunction event during meiosis II in the female. Nondisjunction will occur when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. An XX egg is produced which, when fertilized with a Y sperm, yields XXY offspring.

In mammals with more than one X chromosome, the genes on all but one X chromosome are not expressed; this is known as X inactivation. This happens in XXY males as well as normal XX females.[18] However, in XXY males, a few genes located in the pseudoautosomal regions of their X chromosomes, have corresponding genes on their Y chromosome and are capable of being expressed.[19]

The first published report of a man with a 47,XXY karyotype was by Patricia A. Jacobs and Dr. J.A. Strong at Western General Hospital in Edinburgh, Scotland in 1959.[20] This karyotype was found in a 24-year-old man who had signs of Klinefelter syndrome. Dr. Jacobs described her discovery of this first reported human or mammalian chromosome aneuploidy in her 1981 William Allan Memorial Award address.[21]

Variations

The 48, XXYY (male) syndrome occurs in 1 in 18,000–40,000 births and has traditionally been considered to be a variation of Klinefelter syndrome. XXYY tetrasomy is no longer generally considered a variation of KS, although it has not yet been assigned an ICD-10 code.

Males with Klinefelter syndrome may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Mosaicism 47,XXY/46,XX with clinical features suggestive of Klinefelter syndrome is very rare. Thus far, only about 10 cases have been described in literature.[22]

Treatment

The genetic variation is irreversible. Testosterone treatment is an option for some individuals who desire a more masculine appearance and identity.[23] Often individuals that have noticeable breast tissue or hypogonadism experience depression and/or social anxiety because they are outside of social norms. This is academically referred to as psychosocial morbidity.[24] At least one study indicates that planned and timed support should be provided for young men with Klinefelter syndrome to ameliorate current poor psychosocial outcomes.[24]

By 2010 over 100 successful pregnancies have been reported using IVF technology with surgically removed sperm material from men with Klinefelter syndrome.[25]

See also

References

  1. ^ 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. pp. 179. ISBN 0-7216-0187-1. 
  2. ^ Bock, Robert (August 1993). "Understanding Klinefelter Syndrome: A Guide for XXY Males and their Families". NIH Pub. No. 93-3202. Office of Research Reporting, NICHD. http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm. Retrieved 2007-04-07. 
  3. ^ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. p 549. ISBN 0721629210.
  4. ^ a b The Focus Foundation. X & Y Variations. thefocusfoundation.org
  5. ^ a b c "Klinefelter Syndrome". Health Information. National Institute of Health and Human Development. 2007-02-19. http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm. Retrieved 2007-03-24.  and "Klinefelter syndrome". Genetics Home Reference. National Library of Medicine. 2006. http://ghr.nlm.nih.gov/condition%3Dklinefeltersyndrome. Retrieved 2007-03-24.  both provide statistical estimates.
  6. ^ Russell, Liane Brauch (9 June 1961). "Genetics of Mammalian Sex Chromosomes MOUSE STUDIES THROW LIGHT ON THE FUNCTIONS AND ON THE OCCASIONALLY ABERRANT BEHAVIOR OF SEX CHROMOSOMES". Science 133 (3467): 1795–1803. doi:10.1126/science.133.3467.1795 
  7. ^ Klinefelter, HF Jr; Reifenstein, EC Jr; Albright, F. (1942). "Syndrome characterized by gynecomastia, aspermatogenesis without a-Leydigism and increased excretion of follicle-stimulating hormone". J Clin Endocrinol Metab 2 (11): 615–624. doi:10.1210/jcem-2-11-615 . Klinefelter, HF (1986). "Klinefelter syndrome: historical background and development". South Med J 79 (45): 1089–1093. doi:10.1097/00007611-198609000-00012. PMID 3529433  talks about the history of the development of the literature.
  8. ^ Denschlag, Dominik, MD; Clemens, Tempfer, MD; Kunze, Myriam, MD; Wolff, Gerhard, MD; Keck, Christoph, MD (October 2004). "Assisted reproductive techniques in patients with Klinefelter syndrome: A critical review". Fertility and Sterility 82 (4): 775–779. doi:10.1016/j.fertnstert.2003.09.085. PMID 15482743 
  9. ^ Graham, JM Jr; Bashir, AS; Stark, RE; Silbert, A; Walzer, S (June 1988). "Oral and written language abilities of XXY boys: implications for anticipatory guidance". Pediatrics 81 (6): 795–806. PMID 3368277 
  10. ^ Boone KB; Swerdloff RS; Miller BL et al. (May 2001). "Neuropsychological profiles of adults with Klinefelter syndrome". J Int Neuropsychol Soc 7 (4): 446–56. doi:10.1017/S1355617701744013. PMID 11396547. 
  11. ^ Samango-Sprouse, CA. "Expansion of the phenotypic profile of the young child with XXY." Pediatric Endocrinology Reviews. (2010): 160-68
  12. ^ Abstract of Klinefelter, HF (1986). "Klinefelter syndrome: historical background and development". South Med J 79 (9): 1089–1093. doi:10.1097/00007611-198609000-00012. PMID 3529433  provides information on microorchidism (small testes), hypogonadism (infertility/sterility and androgen hormone function) and gynecomastia. Bock, Robert (August 1993). "Understanding Klinefelter Syndrome: A Guide for XXY Males and Their Families". NIH Pub. No. 93-3202. Office of Research Reporting, NICHD. http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm. Retrieved 2007-03-28.  offers substantive information about body type and appearance until a more rigorous source is found/supplied.
  13. ^ Bock, Robert (August 1993). "Understanding Klinefelter Syndrome: A Guide for XXY Males and Their Families, Adolescence section". NIH Pub. No. 93-3202. Office of Research Reporting, NICHD. http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm#xadol. Retrieved 2007-03-29.  describes statistical occurrence of gynecomastia and surgical treatment.
  14. ^ a b Leask, Kathryn (October 2005). "Klinefelter syndrome". National Library for Health, Specialist Libraries, Clinical Genetics. National Library for Health. http://www.library.nhs.uk/genepool/ViewResource.aspx?resID=104897. Retrieved 2007-04-07. 
  15. ^ Hultborn, R; Hanson, C; Kopf, I; Verbiene, I; Warnhammar, E; Weimarck, A (1997 November–December). "Prevalence of Klinefelter syndrome in male breast cancer patients". Anticancer Res. 17 (6D): 4293–4297. PMID 9494523 
  16. ^ For instance, while Hultborn, R; Hanson, C; Kopf, I; Verbiene, I; Warnhammar, E; Weimarck, A (1997 November–December). "Prevalence of Klinefelter syndrome in male breast cancer patients". Anticancer Res. 17 (6D): 4293–4297. PMID 9494523  shows a 50-fold increased risk of developing breast cancer versus normal males, study of the SEER Cancer Statistics Review (CSR) databases available at the National Cancer Institute reveal that female relative risk of breast cancer incidence compared to normal males is around a 100 to 200-fold increase, which indicates XXY males may not be as much at risk statistically as normal females are.
  17. ^ Caroline Mansfield, Suellen Hopfer, Theresa M. Marteau (1999). "Termination rates after prenatal diagnosis of Down syndrome, spina bifida, anencephaly, and Turner and Klinefelter syndromes: a systematic literature review". Prenatal Diagnosis 19 (9): 808–812. doi:10.1002/(SICI)1097-0223(199909)19:9<808::AID-PD637>3.0.CO;2-B. interscience.wiley.com, PMID 10521836 This is similar to 90% results found by David W. Britt, Samantha T. Risinger, Virginia Miller, Mary K. Mans, Eric L. Krivchenia, Mark I. Evans (1999). "Determinants of parental decisions after the prenatal diagnosis of Down syndrome: Bringing in context". American Journal of Medical Genetics 93 (5): 410–416. doi:10.1002/1096-8628(20000828)93:5<410::AID-AJMG12>3.0.CO;2-F. PMID 10951466
  18. ^ Chow J, Yen Z, Ziesche S, Brown C (2005). "Silencing of the mammalian X chromosome". Annu Rev Genomics Hum Genet 6: 69–92. doi:10.1146/annurev.genom.6.080604.162350. PMID 16124854. 
  19. ^ Blaschke RJ, Rappold G (2006). "The pseudoautosomal regions, SHOX and disease. Curr Opin Genet Dev". Jun; 16 (3): 233–9. doi:10.1016/j.gde.2006.04.004. PMID 16650979. 
  20. ^ Jacobs PA, Strong JA (January 31, 1959). "A case of human intersexuality having a possible XXY sex-determining mechanism". Nature 183 (4657): 302–3. doi:10.1038/183302a0. PMID 13632697. 
  21. ^ Jacobs PA (September 1982). "The William Allan Memorial Award address: human population cytogenetics: the first twenty-five years". Am J Hum Genet 34 (5): 689–98. PMC 1685430. PMID 6751075. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1685430. 
  22. ^ Velissariou V, Christopoulou S, Karadimas C, Pihos I, Kanaka-Gantenbein C, Kapranos N, Kallipolitis G, Hatzaki A. (2006). "Rare XXY/XX mosaicism in a phenotypic male with Klinefelter syndrome: case report". Eur J Med Genet 49 (4): 331–337. doi:10.1016/j.ejmg.2005.09.001. PMID 16829354. 
  23. ^ "Androgen deficiency and replacement therapy in men".
  24. ^ a b Simm PJ, Zacharin MR (April 2006). "The psychosocial impact of Klinefelter syndrome--a 10 year review". J. Pediatr. Endocrinol. Metab. 19 (4): 499–505. PMID 16759035. 
  25. ^ Fullerton G, Hamilton M, Maheshwari A. (2010). "Should non-mosaic Klinefelter syndrome men be labelled as infertile in 2009?". Hum Reprod. 2010 Mar;25(3):588–97. Epub 2010 Jan 19. 25 (3): 588–97. doi:10.1093/humrep/dep431. PMID 20085911. 

Further reading

External links

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