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a condition in males characterized by small testes, with fibrosis and hyalinization of seminiferous tubules, impairment of function and clumping of Leydig cells, and an increase in urinary gonadotropins, associated with an abnormality of the sex chromosomes. It is associated typically with an XXY chromosome complement.
Etymology: Harry F. Klinefelter, American physician, 1912-1990
a condition of gonadal defects appearing in males after puberty, caused by an extra X chromosome in at least one cell line. Characteristics are small firm testes, long legs, gynecomastia, poor social adaptation, subnormal intelligence, chronic pulmonary disease, and varicose veins. The severity of the abnormalities increases with greater numbers of X chromosomes. The most common abnormality is a 47 XXY karyotype. Men with the karyotype XXXXY have marked congenital malformations and mental retardation.
Klinefelter syndromeA syndrome with a 47, XXY chromosome complement, in which the subjects are phenotypically male but have seminiferous tubule dysgenesis, elevated plasma and urinary gonadotropins, variable gynecomastia, eunuchoid habitus and possibly female secondary sex characteristics. Some patients are chromosomal mosaics, with two or more cell lines of different chromosome constitution.
Klinefelter's syndromeA male bodily disorder caused by one or more additional X (sex) chromosomes. Instead of the normal X and Y sex chromosomes, men with Klinefelter's syndrome have an XXY configuration. This has a feminizing effect. The penis and testicles are small and there may be female breast development and diminished sexual interest (libido). Homosexuality and transvestism are common. The diagnosis can easily be confirmed by chromosomal analysis. Hormonal and plastic surgical treatment can help. (Harry Fitch Kleinfelter, American physician, b. 1912)
Klinefelter's syndromea human chromosomal abnormality in which there is an extra X-chromosome making a complement of 44 autosomes plus XXY (47 in all). The affected individuals are male (showing the SEX DETERMINATION role of the Y-chromosomes) but with much reduced fertility, and a number of female secondary sexual characteristics, such as breasts, often occur. About 1 in 1000 liveborn males are affected by this condition, which arises from NONDISJUNCTION in one or other parent, more probably the female where there is a distinct positive age effect (as in DOWN'S SYNDROME).
Chromosomal abnormality characterized by small testes and male infertility.
Mentioned in: Follicle-Stimulating Hormone Test
a condition in humans characterized by the presence of small testes, with fibrosis and hyalinization of the seminiferous tubules, impairment of function and clumping of Leydig cells, and an increase in urinary gonadotropins, associated with an abnormality of the sex chromosomes. It is associated typically with an XXY chromosome complement. A similar condition is seen in male tortoiseshell and white cats, and has been recorded rarely in stallions, bulls, rams and dogs.
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