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. Genetics Home Reference has merged with MedlinePlus. Learn more.
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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.
The results of one study on non- mosaic XXY infants younger than 2 years indicated that most XXY babies had normal external genitalia and facial features with height and weight in the normal range.
Early diagnosis of Klinefelter syndrome is shown to be important to monitor potential developmental problems. However, most move toward full independence from their families as they enter adulthood. Some have completed graduate education and have a normal level of functioning. Lifespan is not affected by Klinefelter syndrome. Statistics Statistics. It is estimated that 1 in every to 1, newborn males has an extra X chromosome, making Klinefelter syndrome one of the most common chromosomal disorders seen among newborns.
In addition, the features of this condition vary and can overlap significantly with those of other conditions. Do you have updated information on this disease? We want to hear from you. Research Research. Clinical Research Resources ClinicalTrials.
Click on the link to go to ClinicalTrials. Please note: Studies listed on the ClinicalTrials. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more.
To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query". Organizations Organizations. Organizations Supporting this Disease. InterConnect E-mail: info interconnect. Living with XXY W. Point Loma Blvd. Do you know of an organization? Living With Living With. Their Web site offers general and condition-specific education resources to help teachers and parents better understand the needs of students who have genetic conditions.
Learn More Learn More. Click on the link to view information on this topic. MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic. MedlinePlus Genetics contains information on Klinefelter syndrome. This website is maintained by the National Library of Medicine.
This chromosome carries extra copies of genes, which interfere with the development of the testicles and mean they produce less testosterone male sex hormone than usual. The extra genetic information may either be carried in every cell in the body or it may only affect some cells known as mosaic Klinefelter syndrome. Klinefelter syndrome is not directly inherited — the additional X chromosome occurs as a result of either the mother's egg or the father's sperm having the extra X chromosome an equal chance of this happening in either , so after conception the chromosome pattern is XXY rather than XY.
This change in the egg or sperm seems to happen randomly. If you have a son with the condition, the chances of this happening again are very small. But the risk of a woman having a son with Klinefelter syndrome may be slightly higher if the mother is over 35 years of age.
See your GP if you have concerns about your son's development or you notice any troubling symptoms of Klinefelter syndrome in yourself or your son. Klinefelter syndrome is not necessarily anything serious, but treatment can help reduce some of the symptoms if necessary. Your GP may suspect Klinefelter syndrome after a physical examination and may suggest sending off a sample of blood to check reproductive hormone levels. The diagnosis can be confirmed by checking a sample of blood for the presence of the extra X chromosome.
The condition may go undiagnosed until adulthood or it may never be diagnosed. For others, the condition has a noticeable effect on growth or appearance. Klinefelter syndrome occurs as a result of a random error that causes a male to be born with an extra sex chromosome. It isn't an inherited condition. Humans have 46 chromosomes, including two sex chromosomes that determine a person's sex.
Females have two X sex chromosomes XX. Males have an X and a Y sex chromosome XY. Extra copies of genes on the X chromosome can interfere with male sexual development and fertility.
Klinefelter syndrome stems from a random genetic event. The risk of Klinefelter syndrome isn't increased by anything a parent does or doesn't do. For older mothers, the risk is higher but only slightly. A number of complications caused by Klinefelter syndrome are related to low testosterone hypogonadism. Testosterone replacement therapy reduces the risk of certain health problems, especially when therapy is started at the beginning of puberty.
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