Synonyms
Klinefelder Syndrom
Definition and Characteristics
Klinefelter syndrome is characterized by addition of one extra X chromosome to a male 46, XY karyotype. Consistent clinical features include increased mean height and infertility. The extra X chromosome results from non-disjunction of sex-chromosomes during the first (or less frequently the second) meiotic division in either parent. It is contributed slightly more often by the mother than the father [1]. There is an age effect for the cases where both X chromosomes originate from the mother.
Prevalence
Klinefelter syndrome is the most common sex chromosome aneuploidy in men, the estimated frequency is 1:500–1:1,000 male births.
Genes
Klinefelter syndrome is due to addition of one extra X chromosome (47, XXY).
Features and Natural History
Somatic phenotype
Infancy and childhood: Newborns usually show no significant dysmorphisms. Weight, height and head circumference at birth are within normal ranges.
Pre-pubertal boys: Height...
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References
Harvey J, Jacobs PA, Hassold T, Pettay D (1990) The parental origin of 47, XXY males. Birth Defects Orig Artic Ser 26(4):289–296
Nielsen J, Pelsen B (1987) Follow-up 20 years later of 34 Klinefelter males with karyotype 47, XXY and 16 hypogonadal males with karyotype 46, XY. Hum Genet 77(2):188–192
Kebers F, Janvier S, Colin A, Legros JJ, Ansseau M (2002) What is the interest of Klinefelter’s syndrome for (child) psychiatrists? Encephale 28(3 Pt 1):260–265
Hasle H, Mellemgaard A, Nielsen J, Hansen J (1995) Cancer incidence in men with Klinefelter syndrome. Br J Cancer 71(2):416–420
Hultborn R, Hanson C, Kopf I, Verbiene I, Warnhammar E, Weimarck A (1997) Prevalence of Klinefelter’s syndrome in male breast cancer patients. Anticancer Res 17(6D):4293–4297
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© 2009 Springer-Verlag GmbH Berlin Heidelberg
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Bartholdi, D., Schinzel, A. (2009). X Polysomy, in Males. In: Lang, F. (eds) Encyclopedia of Molecular Mechanisms of Disease. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-29676-8_3395
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DOI: https://doi.org/10.1007/978-3-540-29676-8_3395
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-67136-7
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