Feb 14, · Klinefelter syndrome is a genetic condition in which a boy is born with an extra X chromosome. Instead of the typical XY chromosomes in men, they have XXY, so this condition is sometimes called XXY Estimated Reading Time: 2 mins. Some boys will even have more than two X chromosomes (XXXY or XXXXY, for example), which increases the risk of severe symptoms and other health concerns. When a boy is born with the XXY condition in only some of his cells, it's called mosaic Klinefelter syndrome. Often, boys and men with this condition can have milder signs and symptoms than others with the XXY condition.
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Menu Search Home Diseases 47, XXY. You can help advance rare hwen research! Not a rare disease. Klinefelter syndrome. This disease is grouped under:. Numeric sex chromosome variations. Summary Summary. Symptoms Symptoms. Some people with 47, XXY do not have any noticeable signs or symptoms features associated with the chromosome variation. Others may have features that range from mild to severe.
Puberty and adulthood is when differences may chgomosomes more clear. One of the most common features shared by males with 47, XXY is hypogonadismwhich means the testes do not produce enough testosterone. Other than a small period in infancy, testosterone production is not important until puberty. Low testosterone may cause some boys with 47, XXY to have delayed or incomplete puberty, as well as may worsen concentration, mood, and behavioral problems. For others, the low testosterone may not cause noticeable symptoms until adulthood when low sexual drive and tiredness may develop and continue to worsen with age.
For some men, infertility caused by no or low sperm count may be the first detected symptom. KS is the name of a collection of features that include decreased testosterone production primary hypogonadismsmall testes, enlarged breast tissue gynecomastiatall stature, long legs, wide hips, learning disabilities, behavioral problems, and social relational problems. KS can also be caused by other sex chromosome variations.
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Patient Registry A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with 47, XXY.
The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information.
Learn more about registries. Organizations Organizations. Organizations Supporting this Disease. Do you know of an organization? Learn More Learn More. Click on the link to view a sample search on this topic. Have a question? References References. Klinefelter syndrome KS : genetics, clinical phenotype and hypogonadism.
Journal of Endocrinological Investigation. Klinefelter Syndrome and medical treatment: hypogonadism and beyond. Hormones Athens. Oct-Dec ; 14 4 De novo structure variations of the Y chromosome in a 47,XXY female with ovarian failure: a case report. Cytogenet Genome Res. Fruhmesser A. Kotzot D. Chromosomal variants in Klinefelter syndrome. Sexual Development. Do you know of a review article? Share this content:. Close Copy Link. You May Be Interested In. How to Find a Disease Specialist.
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Oct 18, · People with 47, XXY have two X chromosomes and one Y chromosome. Some people with 47, XXY may have no noticeable signs or symptoms (features) or only mild features. Others may have more moderate to severe features. Common symptoms of 47, XXY include low testosterone, infertility, speech and language problems, and learning difficulties. Mar 31, · Klinefelter syndrome, also known as the XXY condition, is a term used to describe males who have an extra X chromosome in most of their cells. Instead of having the usual XY chromosome pattern that most males have, these men have an XXY pattern.
Klinefelter syndrome is a chromosomal condition in boys and men that can affect physical and intellectual development. Most commonly, affected individuals are taller than average are unable to father biological children infertile ; however the signs and symptoms of Klinefelter syndrome vary among boys and men with this condition.
In some cases, the features of the condition are so mild that the condition is not diagnosed until puberty or adulthood, and researchers believe that up to 75 percent of affected men and boys are never diagnosed. Boys and men with Klinefelter syndrome typically have small testes that produce a reduced amount of testosterone primary testicular insufficiency. Testosterone is the hormone that directs male sexual development before birth and during puberty.
Without treatment, the shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement gynecomastia , decreased muscle mass, decreased bone density, and a reduced amount of facial and body hair.
As a result of the small testes and decreased hormone production, affected males are infertile but may benefit from assisted reproductive technologies. Some affected individuals also have differences in their genitalia, including undescended testes cryptorchidism , the opening of the urethra on the underside of the penis hypospadias , or an unusually small penis micropenis.
Other physical changes associated with Klinefelter syndrome are usually subtle. Older children and adults with the condition tend to be somewhat taller than their peers. Other differences can include abnormal fusion of certain bones in the forearm radioulnar synostosis , curved pinky fingers fifth finger clinodactyly , and flat feet pes planus.
Children with Klinefelter syndrome may have low muscle tone hypotonia and problems with coordination that may delay the development of motor skills, such as sitting, standing, and walking.
Affected boys often have learning disabilities, resulting in mild delays in speech and language development and problems with reading. Boys and men with Klinefelter syndrome tend to have better receptive language skills the ability to understand speech than expressive language skills vocabulary and the production of speech and may have difficulty communicating and expressing themselves.
About 10 percent of boys and men with Klinefelter syndrome have autism spectrum disorder. Nearly half of all men with Klinefelter syndrome develop metabolic syndrome, which is a group of conditions that include type 2 diabetes , high blood pressure hypertension , increased belly fat, high levels of fats lipids such as cholesterol and triglycerides in the blood.
Compared with unaffected men, adults with Klinefelter syndrome also have an increased risk of developing involuntary trembling tremors , breast cancer if gynecomastia develops , thinning and weakening of the bones osteoporosis , and autoimmune disorders such as systemic lupus erythematosus and rheumatoid arthritis.
Autoimmune disorders are a large group of conditions that occur when the immune system attacks the body's own tissues and organs. Klinefelter syndrome affects about 1 in newborn boys. It is among the most common sex chromosome disorders, which are conditions caused by changes in the number of sex chromosomes the X chromosome and the Y chromosome. Klinefelter syndrome is a sex chromosome disorder in boys and men that results from the presence of an extra X chromosome in cells.
People typically have 46 chromosomes in each cell, two of which are the sex chromosomes. Most often, boys and men with Klinefelter syndrome have the usual X and Y chromosomes, plus one extra X chromosome, for a total of 47 chromosomes 47,XXY. Boys and men with Klinefelter syndrome have an extra copy of multiple genes on the X chromosome. The activity of these extra genes may disrupt many aspects of development, including sexual development before birth and at puberty, and are responsible for the common signs and symptoms of Klinefelter syndrome.
Researchers are working to determine which genes contribute to the specific developmental and physical differences that can occur with Klinefelter syndrome. Some people with features of Klinefelter syndrome have an extra X chromosome in only some of their cells; other cells typically have one X and one Y chromosome. Rarely, other cells may have additional chromosome abnormalities.
It is thought that less than 10 percent of individuals with Klinefelter syndrome have the mosaic form. Boys and men with mosaic Klinefelter syndrome may have milder signs and symptoms than those with the extra X chromosome in all of their cells, depending on what proportion of cells have the additional chromosome. Several conditions resulting from the presence of more than one extra sex chromosome in each cell are sometimes described as variants of Klinefelter syndrome.
Like Klinefelter syndrome, these conditions affect male sexual development and can be associated with learning disabilities and problems with speech and language development.
However, the features of these disorders tend to be more severe than those of Klinefelter syndrome and affect more parts of the body. As doctors and researchers have learned more about the differences between these sex chromosome disorders, they have started to consider them as separate conditions.
Klinefelter syndrome is not inherited; the addition of an extra X chromosome occurs during the formation of reproductive cells eggs or sperm in one of an affected person's parents. During cell division , an error called nondisjunction prevents X chromosomes from being distributed normally among reproductive cells as they form. Typically, as cells divide, each egg cell gets a single X chromosome, and each sperm cell gets either an X chromosome or a Y chromosome. However, because of nondisjunction, an egg cell or a sperm cell can also end up with an extra copy of the X chromosome.
If an egg cell with an extra X chromosome XX is fertilized by a sperm cell with one Y chromosome, the resulting child will have Klinefelter syndrome. Similarly, if a sperm cell with both an X chromosome and a Y chromosome XY fertilizes an egg cell with a single X chromosome, the resulting child will have Klinefelter syndrome. It occurs as a random error during cell division early in fetal development. As a result, some of the body's cells have the usual one X chromosome and one Y chromosome 46,XY , and other cells have an extra copy of the X chromosome 47,XXY.
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Users with questions about a personal health condition should consult with a qualified healthcare professional. Klinefelter syndrome. From Genetics Home Reference. Description Klinefelter syndrome is a chromosomal condition in boys and men that can affect physical and intellectual development. Frequency Klinefelter syndrome affects about 1 in newborn boys.
Causes Klinefelter syndrome is a sex chromosome disorder in boys and men that results from the presence of an extra X chromosome in cells. Learn more about the chromosome associated with Klinefelter syndrome x chromosome.
Inheritance Klinefelter syndrome is not inherited; the addition of an extra X chromosome occurs during the formation of reproductive cells eggs or sperm in one of an affected person's parents. Research Studies from ClinicalTrials. The cognitive phenotype in Klinefelter syndrome: a review of the literature including genetic and hormonal factors. Dev Disabil Res Rev. Adv Pediatr. Chromosomal variants in klinefelter syndrome. Sex Dev. Epub Apr Klinefelter syndrome: clinical and molecular aspects.
Expert Rev Mol Diagn. Clinical review: Klinefelter syndrome--a clinical update. J Clin Endocrinol Metab. Epub Nov 1. Thinking outside the square: considering gender in Klinefelter syndrome and 47, XXY. Int J Androl. Epub Mar The Klinefelter syndrome: current management and research challenges. Citation on PubMed Nieschlag E. Klinefelter syndrome: the commonest form of hypogonadism, but often overlooked or untreated. Dtsch Arztebl Int.
Epub May Consensus statement on diagnosis and clinical management of Klinefelter syndrome. J Endocrinol Invest. It's not all about the testes: medical issues in Klinefelter patients. Fertil Steril. Epub Jun Cancer incidence and mortality in men with Klinefelter syndrome: a cohort study. J Natl Cancer Inst. Acta Paediatr. Epub Apr 8. The spectrum of the behavioral phenotype in boys and adolescents 47,XXY Klinefelter syndrome. Pediatr Endocrinol Rev. J Dev Behav Pediatr.