Klinefelter syndrome
47 XXY syndrome; XXY syndrome; XXY trisomy; 47,XXY/46,XY; 47,XXY/46,XY mosaicism; Poly-X Klinefelter syndromeKlinefelter syndrome, also called 47,XXY, is a genetic condition that occurs in males when they have an extra X chromosome. This can cause problems with development and fertility. Some men have no symptoms and never know they have it.
Causes
Most people have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. The 2 sex chromosomes (X and Y) determine the genetic sex of a child. The genetic sex of a child is determined at conception. The mother's egg cell contains an X chromosome, while the father's sperm cell contains either an X or a Y chromosome.
Normally, an infant inherits 1 pair of sex chromosomes, 1 X from the mother and 1 X or 1 Y from the father. A baby who inherits the X chromosome from the father is a genetic female and has 2 X chromosomes. A baby who inherits the Y chromosome from the father is a genetic male and has 1 X and 1 Y chromosome.
Chromosome
Ambiguous genitalia is a rare condition where a child is born with outer genitals that do not clearly look either male or female. They may have feat...
Read Article Now Book Mark ArticleKlinefelter syndrome results when a male child is born with at least 1 extra X chromosome. They have 47 chromosomes instead of 46. This is written as 47, XXY.
Klinefelter syndrome occurs as a random event. There is no exact cause, and the condition is not inherited.
Klinefelter syndrome occurs in about 1 out of 500 to 1,000 male infants. Women who get pregnant after age 35 are slightly more likely to have a male child with this syndrome than younger women.
Symptoms
Symptoms vary widely, with some males having few or only mild signs. Some may never know they have the condition or only discover it as adults when they have fertility problems. Others experience delayed growth and development in childhood.
Symptoms may include any of the following:
- Urethra on the underside of the penis (hypospadias)
Hypospadias
Hypospadias is a birth (congenital) defect in which the opening of the urethra is on the underside of the penis. The urethra is the tube that carrie...
Read Article Now Book Mark Article - Testicles that have not moved into the scrotum
- Being slow to sit up, walk, crawl, and speak
- Delayed puberty
- Small, firm testicles
Testicles
The testes are 2 egg-shaped male reproductive organs located in the scrotum. They produce sperm and the male hormone, testosterone.
Read Article Now Book Mark Article - Language learning disorders, including dyslexia, which affects reading
- Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
- Enlarged breasts (gynecomastia)
Gynecomastia
When abnormal breast tissue develops in males, it is called gynecomastia. It is important to find out if the excess growth is breast tissue and not ...
Read Article Now Book Mark Article - Less than normal amount of pubic, armpit, and facial hair
- Tall height
- Small penis size
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Infertility
Infertility
Infertility means you cannot get pregnant (conceive). There are 2 types of infertility:Primary infertility refers to couples who have not become preg...
Read Article Now Book Mark Article - Sexual problems
- Social, emotional, or behavioral problems
- Mental health conditions such as depression or anxiety
Exams and Tests
Klinefelter syndrome may first be diagnosed when a man comes to their health care provider because of infertility. Or it may be diagnosed if a male child does not develop normally during puberty. The following tests may be performed:
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Karyotyping (checks the chromosomes)
Karyotyping
Karyotyping is a test to examine chromosomes in a sample of cells. This test can help identify genetic problems as the cause of a disorder or diseas...
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Semen analysis
Semen analysis
Semen analysis measures the amount and quality of a man's semen and sperm. Semen is the thick, white fluid released during ejaculation that contains...
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Blood tests will be done to check hormone levels, including:
-
Estradiol, a type of estrogen
Estradiol, a type of estrogen
An estradiol test measures the amount of a hormone called estradiol in the blood. Estradiol is one of the main types of estrogens.
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Follicle stimulating hormone
Follicle stimulating hormone
The follicle stimulating hormone (FSH) blood test measures the level of FSH in blood. FSH is a hormone released by the pituitary gland, located on t...
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Luteinizing hormone
Luteinizing hormone
The LH blood test measures the amount of luteinizing hormone (LH) in blood. LH is a hormone released by the pituitary gland, located on the undersid...
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Testosterone
Testosterone
A testosterone test measures the amount of the male hormone, testosterone, in the blood. Both men and women produce this hormone. The test described...
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Some cases of Klinefelter syndrome are discovered during prenatal tests for other genetic conditions. Follow-up testing of the baby after birth is needed to confirm the diagnosis.
Treatment
While there is no cure, treatment can help improve symptoms. Depending on symptoms, the health care team may include a number of specialists:
- Endocrinologist
- Speech and language therapist
- Physical therapist
- Mental health counselor
- Infertility specialist
Testosterone therapy may be prescribed. This can help:
- Grow body hair
- Deepen the voice
- Strengthen bones
- Improve muscle strength and bulk
- Improve concentration
- Improve mood and self esteem
- Increase energy and sex drive
Males who have excess breast tissue may decide to have it surgically removed.
If you have Klinefelter syndrome and wish to have children, it's a good idea to work with an infertility specialist. Many men with this syndrome cannot produce enough sperm to have children. However, some men may be helped with newer reproductive technologies.
Support Groups
More information and support for people with Klinefelter syndrome and their families can be found at:
- Association for X and Y Chromosome Variations -- genetic.org
- Living with XXY - livingwithxxy.org/
- US National Library of Medicine, MedlinePlus -- medlineplus.gov/klinefeltersyndrome.html
Possible Complications
Men with Klinefelter syndrome have an increased risk of a number of other health conditions:
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Attention deficient hyperactivity disorder (ADHD)
Attention deficient hyperactivity disor...
Attention deficit hyperactivity disorder (ADHD) is a problem caused by the presence of one or more of these findings:Not being able to focusBeing ove...
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Autism spectrum disorder
Autism spectrum disorder
Autism spectrum disorder (ASD) is a developmental disorder. It often appears in the first 2 to 3 years of life. ASD affects the brain's ability to ...
Read Article Now Book Mark Article - Autoimmune disorders, such as lupus, rheumatoid arthritis, and Sjögren syndrome
Lupus
Systemic lupus erythematosus (SLE) is an autoimmune disease. In this disease, the immune system of the body mistakenly attacks healthy tissue. It c...
Read Article Now Book Mark ArticleRheumatoid arthritis
Rheumatoid arthritis (RA) is a disease that leads to inflammation of the joints and surrounding tissues. It is a long-term disease. It can also aff...
Read Article Now Book Mark ArticleSjögren syndrome
Sjögren syndrome is an autoimmune disorder in which the glands that produce tears and saliva are destroyed. This causes dry mouth and dry eyes. The...
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Breast cancer in men
Breast cancer
Breast cancer is cancer that starts in the tissues of the breast. There are two main types of breast cancer:Ductal carcinoma starts in the tubes (du...
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- Extragonadal germ cell tumor (rare)
-
Lung disease
Lung disease
Lung disease is any problem in the lungs that prevents the lungs from working properly. There are three main types of lung disease:Airway diseases -...
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Osteoporosis
Osteoporosis
Osteoporosis is a disease in which bones become fragile and more likely to break (fracture).
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Varicose veins
Varicose veins
Varicose veins are swollen, twisted, and enlarged veins that you can see under the skin. They are often red or blue in color. They most often appea...
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Metabolic syndrome
Metabolic syndrome
Metabolic syndrome is a name for a group of risk factors that occur together and increase the chance of having coronary artery disease, stroke, and t...
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- Obesity
When to Contact a Medical Professional
Contact your provider if your child has any signs or symptoms of Klinefelter syndrome. Also contact your provider if your child does not develop male sexual characteristics during puberty. This includes facial hair growth and a deeper voice.
Adult males with this condition should see their provider for regular health exams to check for and manage possible health problems.
References
Bacino CA, Lee B. Cytogenetics. In: Kliegman RM, St Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 98
Escobar O, Gurtunca N, Viswanathan P, Witchel SF. Pediatric endocrinology. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 9.
Marcdante KJ, Kliegman RM, Schuh AM. Chromosomal disorders. In: Marcdante KJ, Kliegman RM, Schuh AM, eds. Nelson Essentials of Pediatrics. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 49.
Matsumoto AM, Anawalt BD. Testicular disorders. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 19.
Yu RN, Diamond DA. Disorders of sexual development: etiology, evaluation, and medical management. In: Partin AW, Dmochowski RR, Kavoussi LR, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 48.
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Karyotyping - illustration
Karyotyping is a test used to identify chromosome abnormalities as the cause of malformation or disease. The test can be performed on a sample of blood, bone marrow, amniotic fluid, or placental tissue.
Karyotyping
illustration
Review Date: 3/12/2024
Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.