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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. Males who have Klinefelter syndrome may be described as X-Y males or males with X-Y syndrome. 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 exam, and order a chromosome test called a karyotype.
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 (TEST). During TEST, 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:
|Hormone Health Network|
|8401 Connecticut Avenue|
|Chevy Chase, MD 20815-5817|
The Hormone Health Network is a nonprofit organization started by the Endocrine Society. The organization promotes the prevention, treatment, and cure of hormone-related conditions through public outreach and education.
|Klinefelter Syndrome and Associates (KS&A)|
|P.O. Box 872|
|Pine, CO 80470-0872|
KS&A is focused on Knowledge, Support, and Action. It's a nonprofit education and support organization for people who have Klinefelter syndrome or other conditions caused by extra X and/or Y chromosomes.
|March of Dimes|
|1275 Mamaroneck Avenue|
|White Plains, NY 10605|
The March of Dimes tries to improve the health of babies by preventing birth defects, premature birth, and early death. March of Dimes supports research, community services, education, and advocacy to save babies' lives. The organization's website has information on premature birth, birth defects, birth defects testing, pregnancy, and prenatal care.
|National Human Genome Research Institute, National Institutes of Health (NIH)|
|NIH Building 31, Room 4B09, 31 Center Drive|
|MSC 2152, 9000 Rockville Pike|
|Bethesda, MD 20892-2152|
|Phone:||Phone: (301) 402-0911|
The National Human Genome Research Institute (NHGRI) supports genetic and genomic research, investigation into the ethical, legal, and social implications surrounding genetics research, and educational outreach activities. (Genome refers to a complete gene sequence in a organism.) NHGRI also supports the training of investigators and provides genome information, including fact sheets and school materials, to the public and to health professionals.
|National Institute of Child Health and Human Development|
|P.O. Box 3006|
|Rockville, MD 20847|
The National Institute of Child Health and Human Development (NICHD) is part of the U.S. National Institutes of Health. The NICHD conducts and supports research related to the health of children, adults, and families. NICHD has information on its Web site about many health topics. And you can send specific requests to information specialists.
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.
|Primary Medical Reviewer||John Pope, MD - Pediatrics|
|Specialist Medical Reviewer||Stephen LaFranchi, MD - Pediatrics, Pediatric Endocrinology|
|Last Revised||January 17, 2013|
Last Revised: January 17, 2013
Author: Healthwise Staff
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