Disease or Syndrome
Klinefelter's syndrome
Kline·fel·ter's syn·drome [ klahyn-fel-terz ]
Subclass of:
Sex Chromosome Disorders of Sex Development;
Hypogonadism
Also called:
Klinefelter's Syndrome; XXY; XXY male
Definitions related to klinefelter syndrome:
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A condition caused by the presence of an extra X chromosome resulting in 47,XXY karyotype in an individual with male phenotype. The condition is characterized in childhood by relative tall stature with disproportionately long limbs, and speech/language developmental problems in some patients. Postpubertal findings include small testes, gynecomastia, and infertility.NICHD Pediatric TerminologyU.S. National Cancer Institute, 2021
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A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns (46,XY/47,XXY; 47,XXY/48,XXXY, etc.).NLM Medical Subject HeadingsU.S. National Library of Medicine, 2021
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A genetic disorder in males caused by having one or more extra X chromosomes. Males with this disorder may have larger than normal breasts, a lack of facial and body hair, a rounded body type, and small testicles. They may learn to speak much later than other children and may have difficulty learning to read and write. Klinefelter syndrome increases the risk of developing extragonadal germ cell tumors and breast cancer.NCI Dictionary of Cancer TermsU.S. National Cancer Institute, 2021
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A sex chromosome disorder caused by the presence of an extra X chromosome in the male karyotype. Affected individuals are infertile and have a small penis and testes. They tend to have tall stature and long legs and may have difficulties with speech and language development. Gynecomastia may be present.NCI ThesaurusU.S. National Cancer Institute, 2021
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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...MedlinePlus GeneticsU.S. National Library of Medicine, 2021
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(klinefelter's syndrome) Genetic disease that produces sterile males with small testes lacking sperm due to XXY karyotype.CRISP ThesaurusNational Institutes of Health, 2006
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(klinefelter's syndrome) Klinefelter syndrome (KS) is a condition that occurs in men who have an extra X chromosome. The syndrome can affect different stages of physical, language, and social development. The most common symptom is infertility. Boys may be taller than other boys their age, with more fat around the belly. After puberty, KS boys may have Smaller testes and penis; Breast growth; Less facial and body hair; Reduced muscle tone; Narrower shoulders and wider hips; Weaker bones; Decreased sexual interest; Lower energy. KS males may have learning or language problems. They may be quiet and shy and have trouble fitting in. A genetic test can diagnose KS. There is no cure, but treatments are available. It is important to start treatment as early as possible. With treatment, most boys grow up to have normal lives. Treatments include testosterone replacement therapy and breast reduction surgery. If needed, physical, speech, language, and occupational therapy may also help. NIH: National Institute of Child Health and Human DevelopmentMedlinePlusU.S. National Library of Medicine, 2021
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Klinefelter syndrome is the presence of two or more X chromosomes plus one Y, resulting in a phenotypic male. Diagnosis is based on clinical findings and is confirmed by cytogenetic analysis. Treatment may include testosterone supplementation.Merck & Co., Inc., 2020
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In 1942, Klinefelter et al published a report on 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm. In 1959, these men with Klinefelter syndrome were discovered to have an extra X chromosome (genotype XXY) instead of the usual male sex complement (genotype XY).WebMD, 2019
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Klinefelter syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. Klinefelter syndrome is a genetic condition affecting males, and it often isn't diagnosed until adulthood.Mayo Foundation for Medical Education and Research
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Klinefelter syndrome (KS) is a condition that occurs in males when they have an extra X chromosome. Some males with KS have no obvious signs or symptoms while others may have varying degrees of cognitive, social, behavioral, and learning difficulties. Adults with Klinefelter syndrome may also have primary hypogonadism (decreased...National Center for Advancing Translational Sciences
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Klinefelter syndrome, disorder of the human sex chromosomes that occurs in males. Klinefelter syndrome is one of the most frequent chromosomal disorders in males, occurring in approximately 1 in every 500 to 1,000 males. It results from an unequal sharing of sex chromosomes very soon after...Encyclopedia Britannica, Inc., 2020
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