XX male syndrome, also known as de la Chapelle syndrome, is a rare condition in which an individual with a 46,XX karyotype develops a male phenotype.[2] Synonyms for XX male syndrome include 46,XX testicular difference of sex development (or 46,XX DSD)[3][4][5][6]
In 90 percent of these individuals, the syndrome is caused by the Y chromosome's SRY gene, which triggers male reproductive development, being atypically included in the crossing over of genetic information that takes place between the pseudoautosomal regions of the X and Y chromosomes during meiosis in the father.[2][7] When the X with the SRY gene combines with a normal X from the mother during fertilization, the result is an XX male. Less common are SRY-negative XX males, which can be caused by a mutation in an autosomal or X chromosomal gene.[2] The masculinization of XX males is variable.
This syndrome is diagnosed and occurs in approximately 1:20,000 new-born males, making it much less common than Klinefelter syndrome.[8][9][10] Medical treatment of the condition varies, with medical treatment usually not necessary. The alternative name for XX male syndrome, de la Chapelle syndrome, refers to Finnish scientist Albert de la Chapelle, who first described the condition.[11]
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^Délot EC, Vilain EJ (2003). "Nonsyndromic 46,XX Testicular Disorders/Differences of Sex Development". In Pagon RA, Adam MP, Ardinger HH, Wallace SE, Amemiya A, Bean L, Bird TD, Fong CT, Mefford HC, Smith R, Stephens K (eds.). GeneReviews. University of Washington, Seattle. PMID20301589. Archived from the original on 18 January 2017. Retrieved 12 January 2017.updated 2015
^Berglund A, Johannsen TH, Stochholm K, Aksglaede L, Fedder J, Viuff MH, et al. (August 2017). "Incidence, prevalence, diagnostic delay, morbidity, mortality and socioeconomic status in males with 46,XX disorders of sex development: a nationwide study". Human Reproduction. 32 (8): 1751–1760. doi:10.1093/humrep/dex210. PMID28854582.
^Berglund A, Stochholm K, Gravholt CH (June 2020). "The epidemiology of sex chromosome abnormalities". American Journal of Medical Genetics. Part C, Seminars in Medical Genetics. 184 (2): 202–215. doi:10.1002/ajmg.c.31805. PMID32506765.
^Delachapelle A, Hortling H, Niemi M, Wennstroem J (1964-01-12). "XX sex chromosomes in a human male. First case". Acta Medica Scandinavica. 175 (SUPPL 412): 25–28. doi:10.1111/j.0954-6820.1964.tb04630.x. PMID14154995.