Klinefelter's syndrome

Klinefelter's syndrome

ICD10 = ICD10|Q|98|0|q|90-ICD10|Q|98|4|q|90
ICD9 = ICD9|758.7

Caption = 47,XXY
MedlinePlus =
eMedicineSubj = ped
eMedicineTopic = 1252
MeshID = D007713

Klinefelter's syndrome, 47,XXY or XXY syndrome is a condition caused by a chromosome aneuploidy. Affected individuals have at least two X chromosomes and at least one Y chromosome.cite book |author=Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. |title=Robbins and Cotran pathologic basis of disease |publisher=Elsevier Saunders |location=St. Louis, Mo |year=2005 |pages=179 |isbn=0-7216-0187-1 |oclc= |doi= |accessdate=]

The principal effects are development of small testicles and reduced fertility. A variety of other physical and behavioral differences and problems are common, though severity varies and many boys and men with the condition have few detectable symptoms. The second most common extra chromosome condition, it is named after Dr. Harry Klinefelter, an endocrinologist at Massachusetts General Hospital, Boston, Massachusetts, who first described it in 1942.Citation| last = Klinefelter | first = HF Jr | last2 = Reifenstein | first2 = EC Jr | last3 = Albright | title = Syndrome characterized by gynecomastia, aspermatogenesis without a-Leydigism and increased excretion of follicle-stimulating hormone | journal = J Clin Endocrinol Metab | volume = 2 | pages = 615–624 | date = 1942 | year = 1942 | pmid = . Citation| last = Klinefelter | first = HF | title = Klinefelter's syndrome: historical background and development | journal = South Med J | volume = 79 | issue = 45| pages = 1089–1093 | date = 1986 | year =1986 | pmid = 3529433 talks about the history of the development of the literature.] The condition exists in roughly 1 out of every 500 males.cite web| title = Klinefelter Syndrome | work = Health Information | publisher = National Institute of Health and Human Development | date = 2007-02-19 | url = http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm | format = HTML | accessdate = 2007-03-24 and cite web | title = Klinefelter syndrome | work = Genetics Home Reference | publisher = National Library of Medicine | year = 2006 | url = http://ghr.nlm.nih.gov/condition%3Dklinefeltersyndrome | format = HTML | accessdate = 2007-03-24 both provide statistical estimates.] Because of the extra chromosome, individuals with the condition are usually referred to as "XXY Males", or "47, XXY Males".cite web |url=http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm |title=Understanding Klinefelter Syndrome: A Guide for XXY Males and Their Families |last=Bock |first=Robert |accessdate=2007-04-07 |date = 1993 August |year = 1993 | month = August |format=HTML |work=NIH Pub. No. 93-3202|publisher=Office of Research Reporting, NICHD]

igns and symptoms

Affected males are almost always effectively sterile, although advanced reproductive assistance is sometimes possible.Citation|last = Denschlag|first = Dominik, MD|last2 = Clemens|first2 = Tempfer, MD|last3 = Kunze|first3 = Myriam, MD|last4 = Wolff|first4 = Gerhard, MD|last5 = Keck|first5 = Christoph, MD|title = Assisted reproductive techniques in patients with Klinefelter syndrome: A critical review|journal = Fertility and Sterility|volume = 82|issue = 4|pages = 775–779|date = October 2004|year = 2004|doi = 10.1016/j.fertnstert.2003.09.085] Some degree of language learning impairment may be present,Citation|last = Graham |first = JM Jr|last2 = Bashir |first2 = AS|last3 = Stark |first3 = RE|last4 = Silbert |first4 = A|last5 = Walzer |first5 = S|title = Oral and written language abilities of XXY boys: implications for anticipatory guidance|journal = Pediatrics|volume = 81|issue = 6|pages = 795–806|date = June 1988|year = 1988|pmid = 3368277 ] and neuropsychological testing often reveals deficits in executive functions [cite journal |author=Boone KB, Swerdloff RS, Miller BL, "et al" |title=Neuropsychological profiles of adults with Klinefelter syndrome |journal=J Int Neuropsychol Soc |volume=7 |issue=4 |pages=446–56 |year=2001 |month=May |pmid=11396547 |doi= |url=] . 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).Abstract of Citation|last = Klinefelter |first = HF |title = Klinefelter's syndrome: historical background and development|journal = South Med J |volume = 79 |issue = 9|pages = 1089–1093 |date = 1986 |year = 1986 |pmid = 3529433 provides information on microorchidism (small testes), hypogonadism (infertility/sterility and androgen hormone function) and gynecomastia. cite web |url=http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm |title=Understanding Klinefelter Syndrome: A Guide for XXY Males and Their Families |last=Bock |first=Robert |accessdate=2007-03-28 |date = 1993 August |year = 1993 | month = August |format=HTML |work=NIH Pub. No. 93-3202|publisher=Office of Research Reporting, NICHD offers substantive information about body type and appearance until a more rigorous source is found/supplied.] Gynecomastia is present to some extent in about a third of affected individuals, a slightly higher percentage than in the XY population, but only about 10% of XXY males' gynecomastia is noticeable enough to require surgery.cite web |url=http://www.nichd.nih.gov/publications/pubs/klinefelter.cfm#xadol|title=Understanding Klinefelter Syndrome: A Guide for XXY Males and Their Families, Adolescence section |last=Bock |first=Robert |accessdate=2007-03-29 |date = 1993 August |year = 1993 | month = August |format=HTML |work=NIH Pub. No. 93-3202|publisher=Office of Research Reporting, NICHD describes statistical occurrence of gynecomastia and surgical treatment.]

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 hypogonadism, patients will often have a low serum testosterone level but high serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels.cite web| last = Leask | first = Kathryn | title = Klinefelter syndrome | work = National Library for Health, Specialist Libraries, Clinical Genetics | publisher = National Library for Health | month = October | year = 2005 | url = http://www.library.nhs.uk/genepool/ViewResource.aspx?resID=104897 | format = HTML | accessdate = 2007-04-07 ] Despite this misunderstanding of the term, however, it is true that XXY men often also have "microorchidism" (i.e. small testicles).

The more severe end of the spectrum of symptom expression is also associated with an increased risk of germ cell tumors, breast cancer,Citation|last = Hultborn |first = R|last2 = Hanson |first2 = C|last3 = Kopf |first3 = I|last4 = Verbiene |first4 = I|last5 = Warnhammar |first5 = E|last6 = Weimarck |first6 = A |title = Prevalence of Klinefelter's syndrome in male breast cancer patients |journal = Anticancer Res.|volume = 17 |issue = 6D |pages = 4293–4297 |date = 1997 Nov-Dec |year = 1997|pmid = 9494523] and osteoporosis, risks shared to varying degreesFor instance, while Citation|last = Hultborn |first = R|last2 = Hanson |first2 = C|last3 = Kopf |first3 = I|last4 = Verbiene |first4 = I|last5 = Warnhammar |first5 = E|last6 = Weimarck |first6 = A |title = Prevalence of Klinefelter's syndrome in male breast cancer patients |journal = Anticancer Res.|volume = 17 |issue = 6D |pages = 4293–4297 |date = 1997 Nov-Dec |year = 1997|pmid = 9494523 shows a 50-fold increased risk of developing breast cancer versus normal males, study of the [http://seer.cancer.gov/csr/1975_2003/ SEER Cancer Statistics Review (CSR)] databases available at the [http://www.cancer.gov/ 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.] with females. Additionally, medical literature shows some individual case studies of Klinefelter's syndrome coexisting with other disorders, such as pulmonary disease, varicose veins, diabetes mellitus, and rheumatoid arthritis, but possible correlations between Klinefelter's and these other conditions are not well characterized or understood.Fact|date=May 2008

In contrast to these potentially increased risks, it is currently thought that rare X-linked recessive conditions occur even 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.


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.


The extra X chromosome is retained because of a nondisjunction event during meiosis (sex cell division). 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.

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.Chow J, Yen Z, Ziesche S, Brown C (2005). "Silencing of the mammalian X chromosome". Annu Rev Genomics Hum Genet 6: 69-92. PMID 16124854] A few genes located in the pseudoautosomal regions, however, have corresponding genes on the Y chromosome and are capable of being expressed.Blaschke RJ, Rappold G (2006). The pseudoautosomal regions, SHOX and disease. "Curr Opin Genet Dev". Jun; 16:233-9. PMID 16650979] These triploid genes in XXY males may be responsible for symptoms associated with Klinefelter's syndrome.Fact|date=March 2007

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.cite journal |author=Jacobs PA, Strong JA |month=January 31, |year=1959 |title=A case of human intersexuality having a possible XXY sex-determining mechanism |journal=Nature |volume=183 |issue=4657 |pages=302–3 |pmid=13632697 |doi= 10.1038/183302a0] This karyotype was found in a 24-year-old man who had signs of Klinefelter's syndrome. Dr. Jacobs described her discovery of this first reported human or mammalian chromosome aneuploidy in her 1981 William Allan Memorial Award address.cite journal |author=Jacobs PA |month=September |year=1982 |title=The William Allan Memorial Award address: human population cytogenetics: the first twenty-five years |journal=Am J Hum Genet |volume=34 |issue=5 |pages=689–98 |pmid=6751075 |pmc=1685430]


The genetic variation is irreversible, but its symptoms can be altered or treated in a number of ways, including the use of testosterone treatment. [Androgen deficiency and replacement therapy in men - http://www.mja.com.au/public/issues/180_10_170504/han10513_fm.html]

Inadequately treated hypogonadism in Klinefelter syndrome increases recognized psychosocial morbidity.cite journal |author=Simm PJ, Zacharin MR |title=The psychosocial impact of Klinefelter syndrome--a 10 year review |journal=J. Pediatr. Endocrinol. Metab. |volume=19 |issue=4 |pages=499–505 |year=2006 |month=April |pmid=16759035 |doi= |url=] 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.


The 48, XXYY (male) syndrome occurs 1 in 17,000 births and has traditionally been considered to be a variation of Klinefelter's syndrome. XXYY 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.Velissariou V, Christopoulou S, Karadimas C, Pihos I, Kanaka-Gantenbein C, Kapranos N, Kallipolitis G, Hatzaki A. (July - August 2006). "Rare XXY/XX mosaicism in a phenotypic male with Klinefelter syndrome: case report". " Eur J Med Genet" 49 (4): 331-337. PMID 16829354]

See also

* Intersexuality
* Mosaic (genetics)
* Triple X syndrome
* Turner syndrome
* XXYY syndrome
* XYY syndrome
* True hermaphroditism


External links


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Look at other dictionaries:

  • Klinefelter's syndrome — ☆ Klinefelter s syndrome [klīn′fel΄tərz ] n. [after H. Klinefelter (1912 ), U.S. physician] a congenital disorder of males, caused by the presence of an extra X chromosome and characterized by small testicles and sterility …   English World dictionary

  • Klinefelter's syndrome — /kluyn fel teuhrz/, Pathol. an abnormal condition in which at least one extra X chromosome is present in a male: characterized by reduced or absent sperm production, small testicles, and in some cases enlarged breasts. [named after Harry Fitch… …   Universalium

  • Klinefelter's syndrome — Kline·fel·ter s syndrome klīn .fel tərz also Kline·fel·ter syndrome tər n an abnormal condition in a male characterized by two X chromosomes and one Y chromosome, infertility, smallness of the testes, sparse facial and body hair, and gynecomastia …   Medical dictionary

  • Klinefelter's syndrome — noun syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male • Syn: ↑Klinefelter… …   Useful english dictionary

  • Klinefelter's syndrome — noun Etymology: Harry F. Klinefelter died 1990 American physician Date: 1950 an abnormal condition in a male characterized by usually two X and one Y chromosomes, infertility, smallness of the testicles, sparse facial and body hair, and enlarged… …   New Collegiate Dictionary

  • Klinefelter's syndrome — [ klʌɪnˌfɛltəz] noun Medicine a syndrome affecting males in which the cells have an extra X chromosome, characterized by a tall thin physique, small infertile testes, and enlarged breasts. Origin 1940s: named after the American physician Harry F …   English new terms dictionary

  • Klinefelter's syndrome — a genetic disorder in which there are three sex chromosomes, XXY, rather than the normal XX or XY. Affected individuals are apparently male, but are tall and thin, with small testes, failure of normal sperm production (azoospermia), enlargement… …   The new mediacal dictionary

  • Klinefelter's syndrome — n. (Genetics) XXY syndrome, disorder in males caused by the presence of an extra X chromosome (characterized by small testicles, decreased sperm production, gynecomastia, long legs and mental retardation) …   English contemporary dictionary

  • Klinefelter's syndrome — Human genetic abnormality in which the individual, phenotypically apparently male, has three sex chromosomes (XXY) …   Dictionary of molecular biology

  • Синдром Кляйнфелтера (Klinefelter'S Syndrome) — генетическое нарушение, при котором в организме человека присутствует три половых хромосомы XXY, вместо обычных двух (XX или XY). Данное нарушение поражает исключительно представителей мужского пола; при этом больной выглядит высоким и худым,… …   Медицинские термины

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