Klinefelter's syndrome

Klinefelter's syndrome
/kluyn"fel teuhrz/, Pathol.
an abnormal condition in which at least one extra X chromosome is present in a male: characterized by reduced or absent sperm production, small testicles, and in some cases enlarged breasts.
[named after Harry Fitch Klinefelter (born 1912), U.S. physician, co-author of a description of the syndrome]

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      relatively common (one per 500 live male births) human sex-chromosome (sex chromosome) disorder. It is characterized by the following: small testes, lack of sperm formation, late puberty with reduced secondary sexual characteristics (but with normal-sized penis), usually a delicate and long-limbed physique, occasionally breast enlargement (gynecomastia), and about a 25 percent frequency of mental retardation but a much higher frequency of behavioral difficulties.

      Treatment with male hormone will normalize male appearance and produce a natural sex drive, but the patient will remain sterile.

      The majority of Klinefelter individuals have one extra female sex chromosome, resulting in an XXY pattern and a total of 47 chromosomes instead of 46. Other, less frequent, chromosomal patterns include XXXY, XXXXY, XXYY, XXXYY, mixtures (mosaics), and partial losses or deletions. About 40 percent of the diagnosed examples of Klinefelter's syndrome have a normal XY pattern. One variant of Klinefelter's syndrome, the XXXXY type, is characterized by fusion of the forearm bones and other skeletal anomalies, underdevelopment of the penis and scrotum, incomplete descent of the testes, and marked mental retardation.

      Diabetes mellitus and goitre incidence are more common, and various cancers may be more prevalent among Klinefelter's syndrome patients. Thyroidal trapping of radioactive iodine and the responses of the thyroid to injections of thyrotropin (TSH; thyroid-stimulating hormone) may be low. Testosterone production tends to be below normal, with urinary 17-ketosteroids in the normal or low-normal range. The serum and urinary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are usually, but not necessarily, increased.

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Universalium. 2010.

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Look at other dictionaries:

  • Klinefelter's syndrome — ☆ Klinefelter s syndrome [klīn′fel΄tərz ] n. [after H. Klinefelter (1912 ), U.S. physician] a congenital disorder of males, caused by the presence of an extra X chromosome and characterized by small testicles and sterility …   English World dictionary

  • Klinefelter's syndrome — Infobox Disease ICD10 = ICD10|Q|98|0|q|90 ICD10|Q|98|4|q|90 ICD9 = ICD9|758.7 Caption = 47,XXY ICDO = OMIM = MedlinePlus = eMedicineSubj = ped eMedicineTopic = 1252 MeshID = D007713 Klinefelter s syndrome, 47,XXY or XXY syndrome is a condition… …   Wikipedia

  • Klinefelter's syndrome — Kline·fel·ter s syndrome klīn .fel tərz also Kline·fel·ter syndrome tər n an abnormal condition in a male characterized by two X chromosomes and one Y chromosome, infertility, smallness of the testes, sparse facial and body hair, and gynecomastia …   Medical dictionary

  • Klinefelter's syndrome — noun syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male • Syn: ↑Klinefelter… …   Useful english dictionary

  • Klinefelter's syndrome — noun Etymology: Harry F. Klinefelter died 1990 American physician Date: 1950 an abnormal condition in a male characterized by usually two X and one Y chromosomes, infertility, smallness of the testicles, sparse facial and body hair, and enlarged… …   New Collegiate Dictionary

  • Klinefelter's syndrome — [ klʌɪnˌfɛltəz] noun Medicine a syndrome affecting males in which the cells have an extra X chromosome, characterized by a tall thin physique, small infertile testes, and enlarged breasts. Origin 1940s: named after the American physician Harry F …   English new terms dictionary

  • Klinefelter's syndrome — a genetic disorder in which there are three sex chromosomes, XXY, rather than the normal XX or XY. Affected individuals are apparently male, but are tall and thin, with small testes, failure of normal sperm production (azoospermia), enlargement… …   The new mediacal dictionary

  • Klinefelter's syndrome — n. (Genetics) XXY syndrome, disorder in males caused by the presence of an extra X chromosome (characterized by small testicles, decreased sperm production, gynecomastia, long legs and mental retardation) …   English contemporary dictionary

  • Klinefelter's syndrome — Human genetic abnormality in which the individual, phenotypically apparently male, has three sex chromosomes (XXY) …   Dictionary of molecular biology

  • Klinefelter syndrome — noun syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male • Syn: ↑Klinefelter… …   Useful english dictionary

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