Klinefelter syndrome is a genetic disorder that affects males. Klinefelter syndrome occurs when a boy is born with one or more extra X chromosomes. Most males have one Y and one X chromosome. Having extra X chromosomes can cause a male to have some physical traits unusual for males.
Many men with an extra X chromosome are not aware that they have it, and they lead normal lives. Klinefelter syndrome occurs in about 1 out of 1,000 males.
The presence of an extra X chromosome in males most often occurs when the genetic material in the egg splits unevenly. But it can also occur when the genetic material in the sperm splits unevenly. Even though Klinefelter syndrome is a genetic disorder, it is not passed down through families. So, parents who have a child with Klinefelter syndrome are not any more likely than other couples to have another child with the condition.
Many men who have Klinefelter syndrome do not have obvious symptoms. Others have sparse body hair, enlarged breasts, and wide hips. In almost all men the testicles remain small. In some men the penis does not reach adult size. Their voices may not be as deep. They usually cannot father children. But they can have a normal sex life.
Some boys with Klinefelter syndrome have language and learning problems.
See a picture of a male with Klinefelter syndrome.
Klinefelter syndrome usually is not diagnosed until the time of puberty. At this point, the boy's testicles fail to grow normally and you may start to notice other symptoms.
To find out if your son has Klinefelter syndrome, your doctor will ask questions about his past health, do a physical examination, and order a chromosome test called a karyotype.
If you are pregnant and at risk for having a child with Klinefelter syndrome, tests may be done. Klinefelter syndrome can be detected before birth (prenatally) through genetic tests on cells collected from amniocentesis or chorionic villus sampling (CVS). But this is not routinely done.
In adult men, lab tests in addition to a karyotype may be done, such as hormone tests or a semen analysis, if Klinefelter syndrome is suspected.
Males with Klinefelter syndrome can be given testosterone, a hormone needed for sexual development. If treatment is started around the age of puberty, it can help boys have more normal body development.
Testosterone is given by injection or through a skin patch or gel. The treatment usually continues throughout a man's life but does not help infertility.
Speech therapy and educational support can help boys who have language or learning problems.
If a man with Klinefelter wants to have children, he may be able to have his sperm collected through testicular sperm extraction (TESE). During TESE, sperm are obtained using a thin needle inserted into the testicle or through a small cut made in the testicle. Normal sperm are identified and then used for in vitro fertilization.
If your son has been diagnosed with Klinefelter syndrome:
Learning about Klinefelter syndrome:
Other Works Consulted
Achermann JC, Hughes IA (2011). Disorders of Sex Development. In S Melmed et al., eds., Williams Textbook of Endocrinology, 12th ed., pp. 868-934. Philadelphia: Saunders.
Bojesen A, et al. (2003). Prenatal and postnatal prevalence of Klinefelter syndrome: A national registry study. Journal of Clinical Endocrinology and Metabolism, 88(2): 622-626.
Braunstein GD (2011). Testes. In DG Gardner, D Shoback, eds., Greenspan's Basic and Clinical Endocrinology, 9th ed., pp. 395-422. New York: McGraw-Hill Medical.
Tsai A C-H, et al. (2012). Genetics and dysmorphology. In WW Hay Jr et al., eds., Current Diagnosis and Treatment: Pediatrics, 21st ed., pp. 1088-1122. New York: McGraw-Hill Medical.
ByHealthwise StaffPrimary Medical ReviewerJohn Pope, MD - PediatricsBrian D. O'Brien, MD - Internal MedicineSpecialist Medical ReviewerStephen LaFranchi, MD - Pediatrics, Pediatric EndocrinologySiobhan M. Dolan, MD, MPH - Reproductive Genetics
Current as ofOctober 9, 2017
Current as of: October 9, 2017
John Pope, MD - Pediatrics
& Brian D. O'Brien, MD - Internal Medicine & Stephen LaFranchi, MD - Pediatrics, Pediatric Endocrinology & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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