Laboratory Studies

Prenatal and postnatal diagnostic testing

Klinefelter syndrome may be diagnosed prenatally from fetal cytogenetic analyses performed on chorionic villi or amniocytes. Noninvasive prenatal tests (NIPT) that analyze cell-free fetal DNA circulating in maternal blood are also available.^{[41, 42]}

If Klinefelter syndrome is not diagnosed prenatally, a patient with 47,XXY karyotype may demonstrate various subtle, age-related clinical signs that would prompt diagnostic testing. These include the following^[34]:

Infants - Hypospadias, small phallus, cryptorchidism (undescended testes)
Toddlers - Developmental delay (especially expressive language skills), hypotonia
Elementary school–aged boys - Language delay (especially expressive language skills), learning disabilities, delayed social development, pervasive developmental disorder (PDD-NOS), mild autism spectrum disorder, attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD)
Older boys and adolescent males - Tall stature; delayed or incomplete pubertal development with eunuchoid body habitus; gynecomastia; small, firm testes; sparse body hair
Adults - Testicular failure, significantly diminished or absent sperm count and/or breast malignancy, dental problems, delay in vocational success, anxiety and/or depression, mood disorders

Karyotype analysis on peripheral blood lymphocytes, the XCAT-KS buccal swab test, fluorescence in-situ hybridization (FISH), and microarrays are options for postnatal diagnostic testing.

The 47,XXY karyotype is found in 80-90% of males who are diagnosed with Klinefelter syndrome. About 10% of patients have mosaicism (more than one cell line): 46,XY/47,XXY; 46,XY/48,XXXY; and 47,XXY/48,XXXY. Remaining cases include karyotype variants such as 48,XXYY; 48,XXXY; 49,XXXYY; and 49,XXXXY. About 1% of cases are due to a structurally abnormal X in addition to a normal X and Y, such as 47,X,i(Xq)Y and 47,X,del(X)Y.

Androgen receptor gene quantitative real-time polymerase chain reaction (AR-qPCR) technique

This is a simple and reliable screening method for the diagnosis of patients with Klinefelter syndrome or other chromosomal disorders involving an aberrant number of X chromosomes.^[43]

The screening method determines the copy number assessment of the androgen receptor (AR) gene, located at Xq11.2-Xq12.

Gonadal function

From childhood with progression to early puberty, the pituitary-gonadal function observed is within normal limits for 47,XXY males.^[44]

At midpuberty and later, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations rise to hypergonadotropic levels, inhibin B levels fall until they are undetectable, and testosterone levels are at low or low-normal levels after an initial increase. Hence, most adult males with Klinefelter syndrome have hypergonadotropism with varying degrees of androgen deficiency.^[44]

Hormone testing

A complete hormonal evaluation includes plasma levels of FSH, LH, testosterone, estradiol, prolactin, and insulinlike growth factor (IGF)–1. Young males (aged 12-14 years) tend to have high plasma FSH, LH, and estradiol levels and low plasma testosterone levels.

Forty-seven percent of men with Klinefelter syndrome have adrenal steroidogenic deficiency, so cortisol levels should be routinely measured.^[45]

Serum osteocalcin levels are decreased and the hydroxyl-proline:creatinine ratio is increased, reflecting decreased formation and increased resorption of bone.

Urinary gonadotropins are increased due to abnormal Leydig cell function.

Administration of human chorionic gonadotropin (hCG) will increase testosterone levels in men with Klinefelter syndrome, but the response is diminished when compared with the unaffected male population.

Routine bone density screening

Bone density screening is recommended because androgen deficiency significantly increases the risk of osteopenia and osteoporosis.

Hypercoagulability screening

Men with Klinefelter syndrome have an increased risk of deep vein thrombosis and pulmonary embolism. Consider screening men with 47,XXY or other sex chromosomal aneuploidies for genetic mutations that lead to hypercoagulability states.^[6]

Imaging Studies

Echocardiography is performed to assess for mitral valve prolapse.

Radiography is performed to assess for bone density, radioulnar synostosis, and dental concerns (taurodontism).

Histologic Findings

In prepubertal boys with Klinefelter syndrome, testicular biopsies may reveal preservation of seminiferous tubules with reduced numbers of germ cells; Sertoli and Leydig cells appear normal.^[44]

Testicular biopsies of adult males with Klinefelter syndrome are characterized by extensive fibrosis and hyalinization of the seminiferous tubules and hyperplasia of the interstitium; however, the tubules may show residual foci of spermatogenesis. Histologic findings may include small, firm testes with seminiferous tubular hyalinization; sclerosis; and atrophy with focal hyperplasia of mostly degenerated Leydig cells. Germ cells are markedly deficient or absent.^[44]

In Klinefelter syndrome males with mosaicism, a progressive degeneration and hyalinization of seminiferous tubules occurs following puberty, despite the presence of normal-sized testes and spermatogenesis at puberty.

Histology of gynecomastic breasts reveals hyperplasia of interductal tissue.

Treatment & Management

Klinefelter HF Jr, Reifenstein EC Jr, Albright F. Syndrome characterized by gynecomastia aspermatogenesis without a-Leydigism and increased excretion of follicle-stimulating hormone. J Clin Endocr Metabl. 1942. 2:615-24.
Jacobs PA, Strong JA. A case of human intersexuality having possible XXY sex-determining mechanism. Nature. 1959. 2:164-67.
Visootsak J, Graham JM Jr. Klinefelter syndrome and other sex chromosomal aneuploidies. Orphanet J Rare Dis. 2006 Oct 24. 1:42. [QxMD MEDLINE Link]. [Full Text].
Schiff JD, Palermo GD, Veeck LL, Goldstein M, Rosenwaks Z, Schlegel PN. Success of testicular sperm extraction [corrected] and intracytoplasmic sperm injection in men with Klinefelter syndrome. J Clin Endocrinol Metab. 2005 Nov. 90 (11):6263-7. [QxMD MEDLINE Link].
Damani MN, Mittal R, Oates RD. Testicular tissue extraction in a young male with 47,XXY Klinefelter's syndrome: potential strategy for preservation of fertility. Fertil Steril. 2001 Nov. 76(5):1054-6. [QxMD MEDLINE Link].
Paduch DA, Fine RG, Bolyakov A, Kiper J. New concepts in Klinefelter syndrome. Curr Opin Urol. 2008 Nov. 18(6):621-7. [QxMD MEDLINE Link].
Wikstrom AM, Painter JN, Raivio T, Aittomaki K, Dunkel L. Genetic features of the X chromosome affect pubertal development and testicular degeneration in adolescent boys with Klinefelter syndrome. Clin Endocrinol (Oxf). 2006 Jul. 65(1):92-7. [QxMD MEDLINE Link].
Ramasamy R, Ricci JA, Palermo GD, Gosden LV, Rosenwaks Z, Schlegel PN. Successful fertility treatment for Klinefelter's syndrome. J Urol. 2009 Sep. 182(3):1108-13. [QxMD MEDLINE Link].
Giedd JN, Clasen LS, Wallace GL, et al. XXY (Klinefelter syndrome): a pediatric quantitative brain magnetic resonance imaging case-control study. Pediatrics. 2007 Jan. 119(1):e232-40. [QxMD MEDLINE Link]. [Full Text].
van Rijn S, de Sonneville L, Swaab H. The nature of social cognitive deficits in children and adults with Klinefelter syndrome (47,XXY). Genes Brain Behav. 2018 Feb 6. [QxMD MEDLINE Link].
Seo JT, Lee JS, Oh TH, Joo KJ. The clinical significance of bone mineral density and testosterone levels in Korean men with non-mosaic Klinefelter's syndrome. BJU Int. 2007 Jan. 99(1):141-6. [QxMD MEDLINE Link].
Rovenský J. Rheumatic diseases and Klinefelter's syndrome. Autoimmun Rev. 2006 Nov. 6(1):33-6. [QxMD MEDLINE Link].
Vorona E, Zitzmann M, Gromoll J, Schuring AN, Nieschlag E. Clinical, endocrinological, and epigenetic features of the 46,XX male syndrome, compared with 47,XXY Klinefelter patients. J Clin Endocrinol Metab. 2007 Sep. 92(9):3458-65. [QxMD MEDLINE Link]. [Full Text].
Close S, Fennoy I, Smaldone A, Reame N. Phenotype and Adverse Quality of Life in Boys with Klinefelter Syndrome. J Pediatr. 2015 Sep. 167 (3):650-7. [QxMD MEDLINE Link].
Carlomagno F, Pozza C, Tenuta M, et al. Testicular Microvascular Flow Is Altered in Klinefelter Syndrome and Predicts Circulating Testosterone. J Clin Endocrinol Metab. 2022 Jan 1. 107 (1):e236-45. [QxMD MEDLINE Link]. [Full Text].
Skakkebaek A, Moore PJ, Chang S, Fedder J, Gravholt CH. Quality of life in men with Klinefelter syndrome: the impact of genotype, health, socioeconomics, and sexual function. Genet Med. 2018 Feb. 20 (2):214-22. [QxMD MEDLINE Link].
Paduch DA, Bolyakov A, Cohen P, Travis A. Reproduction in men with Klinefelter syndrome: the past, the present, and the future. Semin Reprod Med. 2009 Mar. 27(2):137-48. [QxMD MEDLINE Link].
Sokol RZ. It's not all about the testes: medical issues in Klinefelter patients. Fertil Steril. 2012 Aug. 98(2):261-5. [QxMD MEDLINE Link].
Robinson A, Bender BG, Linden MG, Salbenblatt JA. Sex chromosome aneuploidy: the Denver Prospective Study. Birth Defects Orig Artic Ser. 1990. 26(4):59-115. [QxMD MEDLINE Link].
Visootsak J, Aylstock M, Graham JM Jr. Klinefelter syndrome and its variants: an update and review for the primary pediatrician. Clin Pediatr (Phila). 2001 Dec. 40(12):639-51. [QxMD MEDLINE Link].
Graham JM Jr, Bashir AS, Stark RE, Silbert A, Walzer S. Oral and written language abilities of XXY boys: implications for anticipatory guidance. Pediatrics. 1988 Jun. 81 (6):795-806. [QxMD MEDLINE Link].
Skakkebaek A, Moore PJ, Pedersen AD, et al. The role of genes, intelligence, personality, and social engagement in cognitive performance in Klinefelter syndrome. Brain Behav. 2017 Mar. 7 (3):e00645. [QxMD MEDLINE Link]. [Full Text].
Boks MP, de Vette MH, Sommer IE, et al. Psychiatric morbidity and X-chromosomal origin in a Klinefelter sample. Schizophr Res. 2007 Jul. 93(1-3):399-402. [QxMD MEDLINE Link].
Völkl TM, Langer T, Aigner T, Greess H, Beck JD, Rauch AM, et al. Klinefelter syndrome and mediastinal germ cell tumors. Am J Med Genet A. 2006 Mar 1. 140(5):471-81. [QxMD MEDLINE Link].
Boada R, Janusz J, Hutaff-Lee C, Tartaglia N. The cognitive phenotype in Klinefelter syndrome: a review of the literature including genetic and hormonal factors. Dev Disabil Res Rev. 2009. 15(4):284-94. [QxMD MEDLINE Link].
Hong DS, Reiss AL. Cognitive and neurological aspects of sex chromosome aneuploidies. Lancet Neurol. 2014 Mar. 13(3):306-18. [QxMD MEDLINE Link].
Lee YS, Cheng AW, Ahmed SF, Shaw NJ, Hughes IA. Genital anomalies in Klinefelter's syndrome. Horm Res. 2007. 68(3):150-5. [QxMD MEDLINE Link].
[Guideline] Centre for Women's and Children's Health. Fertility: assessment and treatment for people with fertility problems. 2004 Feb. 216. [Full Text].
Deebel NA, Galdon G, Zarandi NP, et al. Age-related presence of spermatogonia in patients with Klinefelter syndrome: a systematic review and meta-analysis. Hum Reprod Update. 2020 Jan 1. 26 (1):58-72. [QxMD MEDLINE Link].
Salzano A, Arcopinto M, Marra AM, et al. Klinefelter syndrome, cardiovascular system, and thromboembolic disease: review of literature and clinical perspectives. Eur J Endocrinol. 2016 Jul. 175 (1):R27-40. [QxMD MEDLINE Link]. [Full Text].
Zöller B, Ji J, Sundquist J, Sundquist K. High Risk of Venous Thromboembolism in Klinefelter Syndrome. J Am Heart Assoc. 2016 May 20. 5 (5):[QxMD MEDLINE Link].
Chang S, Christiansen CF, Bojesen A, Juul S, Munster AB, Gravholt CH. Klinefelter syndrome and testosterone treatment: a national cohort study on thrombosis risk. Endocr Connect. 2020 Jan. 9 (1):34-43. [QxMD MEDLINE Link]. [Full Text].
Tartaglia N, Ayari N, Howell S, D'Epagnier C, Zeitler P. 48,XXYY, 48,XXXY and 49,XXXXY syndromes: not just variants of Klinefelter syndrome. Acta Paediatr. 2011 Jun. 100(6):851-60. [QxMD MEDLINE Link]. [Full Text].
Visootsak J, Graham JM Jr. Klinefelter syndrome and other sex chromosomal aneuploidies. Orphanet J Rare Dis. 2006 Oct 24. 1:42. [QxMD MEDLINE Link]. [Full Text].
Jacobs PA, Strong JA. A case of human intersexuality having a possible XXY sex-determining mechanism. Nature. 1959 Jan 31. 183(4657):302-3. [QxMD MEDLINE Link].
Thomas NS, Hassold TJ. Aberrant recombination and the origin of Klinefelter syndrome. Hum Reprod Update. 2003 Jul-Aug. 9(4):309-17. [QxMD MEDLINE Link]. [Full Text].
Lowe X, Eskenazi B, Nelson DO, Kidd S, Alme A, Wyrobek AJ. Frequency of XY sperm increases with age in fathers of boys with Klinefelter syndrome. Am J Hum Genet. 2001 Nov. 69(5):1046-54. [QxMD MEDLINE Link]. [Full Text].
Zitzmann M, Depenbusch M, Gromoll J, Nieschlag E. X-chromosome inactivation patterns and androgen receptor functionality influence phenotype and social characteristics as well as pharmacogenetics of testosterone therapy in Klinefelter patients. J Clin Endocrinol Metab. 2004 Dec. 89(12):6208-17. [QxMD MEDLINE Link].
Bojesen A, Gravholt CH. Klinefelter syndrome in clinical practice. Nat Clin Pract Urol. 2007 Apr. 4(4):192-204. [QxMD MEDLINE Link].
Yencilek F, Baykal C. 46 XX male syndrome: a case report. Clin Exp Obstet Gynecol. 2005. 32 (4):263-4. [QxMD MEDLINE Link].
Allyse M, Minear MA, Berson E, et al. Non-invasive prenatal testing: a review of international implementation and challenges. Int J Womens Health. 2015. 7:113-26. [QxMD MEDLINE Link]. [Full Text].
Samango-Sprouse C, Keen C, Sadeghin T, Gropman A. The benefits and limitations of cell-free DNA screening for 47, XXY (Klinefelter syndrome). Prenat Diagn. 2017 May. 37 (5):497-501. [QxMD MEDLINE Link]. [Full Text].
Ottesen AM, Garn ID, Aksglaede L, Juul A, Rajpert-De Meyts E. A simple screening method for detection of Klinefelter syndrome and other X-chromosome aneuploidies based on copy number of the androgen receptor gene. Mol Hum Reprod. 2007 Oct. 13 (10):745-50. [QxMD MEDLINE Link].
Wikstrom AM, Dunkel L. Testicular function in Klinefelter syndrome. Horm Res. 2008. 69(6):317-26. [QxMD MEDLINE Link].
Mantovani V, Dondi E, Larizza D, et al. Do reduced levels of steroid 21-hydroxylase confer a survival advantage in fetuses affected by sex chromosome aberrations?. Eur J Hum Genet. 2002 Feb. 10(2):137-40. [QxMD MEDLINE Link].
Nieschlag E, Ferlin A, Gravholt CH, et al. The Klinefelter syndrome: current management and research challenges. Andrology. 2016 May. 4 (3):545-9. [QxMD MEDLINE Link].
Samango-Sprouse C, Stapleton EJ, Lawson P, et al. Positive effects of early androgen therapy on the behavioral phenotype of boys with 47,XXY. Am J Med Genet C Semin Med Genet. 2015 Jun. 169 (2):150-7. [QxMD MEDLINE Link].
Ross JL, Kushner H, Kowal K, et al. Androgen Treatment Effects on Motor Function, Cognition, and Behavior in Boys with Klinefelter Syndrome. J Pediatr. 2017 Mar 10. [QxMD MEDLINE Link].
Tournaye H, Staessen C, Liebaers I, et al. Testicular sperm recovery in nine 47,XXY Klinefelter patients. Hum Reprod. 1996 Aug. 11(8):1644-9. [QxMD MEDLINE Link]. [Full Text].
Westlander G, Ekerhovd E, Granberg S, Hanson L, Hanson C, Bergh C. Testicular ultrasonography and extended chromosome analysis in men with nonmosaic Klinefelter syndrome: a prospective study of possible predictive factors for successful sperm recovery. Fertil Steril. 2001 Jun. 75 (6):1102-5. [QxMD MEDLINE Link].
Aboulghar H, Aboulghar M, Mansour R, Serour G, Amin Y, Al-Inany H. A prospective controlled study of karyotyping for 430 consecutive babies conceived through intracytoplasmic sperm injection. Fertil Steril. 2001 Aug. 76(2):249-53. [QxMD MEDLINE Link].
Van Opstal D, Los FJ, Ramlakhan S, et al. Determination of the parent of origin in nine cases of prenatally detected chromosome aberrations found after intracytoplasmic sperm injection. Hum Reprod. 1997 Apr. 12(4):682-6. [QxMD MEDLINE Link]. [Full Text].
Bonduelle M, Aytoz A, Van Assche E, Devroey P, Liebars I, VanSteirteghem A. Incidence of chromosomal aberrations in childrenborn after assisted reproduction through intracytoplasmic sperm injection. Hum Reprod. 1998. 13:781-782. [QxMD MEDLINE Link]. [Full Text].
Staessen C, Coonen E, Van Assche E, et al. Preimplantation diagnosis for X and Y normality in embryos from three Klinefelter patients. Hum Reprod. 1996 Aug. 11(8):1650-3. [QxMD MEDLINE Link]. [Full Text].
Estop AM, Munne S, Cieply KM, Vandermark KK, Lamb AN, Fisch H. Meiotic products of a Klinefelter 47,XXY male as determined by sperm fluorescence in-situ hybridization analysis. Hum Reprod. 1998 Jan. 13(1):124-7. [QxMD MEDLINE Link]. [Full Text].
Reubinoff BE, Abeliovich D, Werner M, Schenker JG, Safran A, Lewin A. A birth in non-mosaic Klinefelter's syndrome after testicular fine needle aspiration, intracytoplasmic sperm injection and preimplantation genetic diagnosis. Hum Reprod. 1998 Jul. 13(7):1887-92. [QxMD MEDLINE Link]. [Full Text].
Rosenlund B, Hreinsson JG, Hovatta O. Birth of a healthy male after frozen thawed blastocyst transfer following intracytoplasmic injection of frozen thawed testicular spermatozoa from a man with nonmosaic Klinefelter's syndrome. J Assist Reprod Genet. 2002 Mar. 19(3):149-51. [QxMD MEDLINE Link].
Hinney B, Guttenbach M, Schmid M, Engel W, Michelmann HW. Pregnancy after intracytoplasmic sperm injection with sperm from a man with a 47,XXY Klinefelter's karyotype. Fertil Steril. 1997 Oct. 68(4):718-20. [QxMD MEDLINE Link].
Palermo GD, Schlegel PN, Sills ES, et al. Births after intracytoplasmic injection of sperm obtained by testicular extraction from men with nonmosaic Klinefelter's syndrome. N Engl J Med. 1998 Feb 26. 338(9):588-90. [QxMD MEDLINE Link].
Ron-El R, Raziel A, Strassburger D, Schachter M, Bern O, Friedler S. Birth of healthy male twins after intracytoplasmic sperm injection of frozen-thawed testicular spermatozoa from a patient with nonmosaic Klinefelter syndrome. Fertil Steril. 2000 Oct. 74(4):832-3. [QxMD MEDLINE Link].
Crüger D, Toft B, Agerholm I, Fedder J, Hald F, Bruun-Petersen G. Birth of a healthy girl after ICSI with ejaculated spermatozoa from a man with non-mosaic Klinefelter's syndrome. Hum Reprod. 2001 Sep. 16(9):1909-11. [QxMD MEDLINE Link]. [Full Text].
Tachdjian G, Frydman N, Morichon-Delvallez N, et al. Reproductive genetic counselling in non-mosaic 47,XXY patients: implications for preimplantation or prenatal diagnosis: Case report and review. Hum Reprod. 2003 Feb. 18(2):271-5. [QxMD MEDLINE Link]. [Full Text].
Close S, Sadler L, Grey M. In the Dark: Challenges of Caring for Sons with Klinefelter Syndrome. J Pediatr Nurs. 2015 May 30. [QxMD MEDLINE Link].
Aguirre D, Nieto K, Lazos M, et al. Extragonadal germ cell tumors are often associated with Klinefelter syndrome. Hum Pathol. 2006 Apr. 37(4):477-80. [QxMD MEDLINE Link].
Swerdlow AJ, Schoemaker MJ, Higgins CD, Wright AF, Jacobs PA,. Cancer incidence and mortality in men with Klinefelter syndrome: a cohort study. J Natl Cancer Inst. 2005 Aug 17. 97(16):1204-10. [QxMD MEDLINE Link].
van Rijn S, Swaab H. Vulnerability for psychopathology in Klinefelter syndrome: age-specific and cognitive-specific risk profiles. Acta Paediatr. 2011 Jun. 100(6):908-16. [QxMD MEDLINE Link].
Horowitz M, Wishart JM, O'Loughlin PD, Morris HA, Need AG, Nordin BE. Osteoporosis and Klinefelter's syndrome. Clin Endocrinol (Oxf). 1992 Jan. 36 (1):113-8. [QxMD MEDLINE Link].
Campbell WA, Price WH. Venous thromboembolic disease in Klinefelter's syndrome. Clin Genet. 1981 Apr. 19(4):275-80. [QxMD MEDLINE Link].
Bardsley MZ, Falkner B, Kowal K, Ross JL. Insulin resistance and metabolic syndrome in prepubertal boys with Klinefelter syndrome. Acta Paediatr. 2011 Jun. 100(6):866-70. [QxMD MEDLINE Link].
Lahlou N, Fennoy I, Ross JL, Bouvattier C, Roger M. Clinical and hormonal status of infants with nonmosaic XXY karyotype. Acta Paediatr. 2011 Jun. 100 (6):824-9. [QxMD MEDLINE Link].
Herlihy AS, McLachlan RI, Gillam L, Cock ML, Collins V, Halliday JL. The psychosocial impact of Klinefelter syndrome and factors influencing quality of life. Genet Med. 2011 Jul. 13 (7):632-42. [QxMD MEDLINE Link].

Media Gallery

Adolescent male with gynecomastia and Klinefelter syndrome.
Child with Klinefelter syndrome. Other than a thin build and disproportionately long arms and legs, the phenotype is normal.
G-banded 47,XXY karyotype.
Adolescent male with Klinefelter syndrome who has female-type distribution of pubic hair and testicular dysgenesis.