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XX male syndrome

XX male syndrome
Classification and external resources
ICD-10 (Q98.3)
OMIM 278850
NCI XX male syndrome
Patient UK XX male syndrome

XX male syndrome (also called de la Chapelle syndrome, for Albert de la Chapelle, who characterized it in 1972[1][2]) is a rare sex chromosomal disorder. Usually, it is caused by unequal crossing over between X and Y chromosomes during meiosis in the father, which results in the X chromosome containing the normally-male SRY gene. When this X combines with a normal X from the mother during fertilization, the result is an XX male.

This syndrome occurs in approximately four or five in 100,000 individuals, making it less common than Klinefelter syndrome.[3][4]


Symptoms usually include small testes and subjects are invariably sterile. Individuals with this condition sometimes have feminine characteristics, with varying degrees of gynecomastia but with no intra-abdominal Müllerian tissue.[5] According to research at the University of Oklahoma health science centers, most XX males are not stereotypically feminine and are typical boys and men[citation needed] although other reports suggest that facial hair growth is usually poor and libido is diminished, with notable exceptions.[5][6]

Clinical diagnosis

  • Standard XX karyotype in two tissues (with at least one, or both, containing the male SRY gene)
  • Male external genitalia, sometimes showing hypospadias
  • Two testes which may or may not have descended the inguinal canal. Most XX males have descended testes.
  • Absence of Müllerian tissue


Males typically have one X chromosome and one Y chromosome in each diploid cell of their bodies. Females typically have two X chromosomes. XX males have two X chromosomes, with one of them containing genetic material from the Y chromosome, making them phenotypically male; they are genetically female but otherwise appear to be male.

See also

External links


  1. ^ de la Chapelle A (1972). "Analytic review: nature and origin of males with XX sex chromosomes". Am J Hum Genet 24 (1): 71–105. PMC 1762158. PMID 4622299. 
  2. ^ de la Chapelle, Albert (1985). Cytogenetics of the mammalian X-chromsome, Part B: Progress and topics in cytogenetics. New York: Alan Liss. p. 75-85. 
  3. ^ Vorona E, Zitzmann M, Gromoll J, Schüring AN, Nieschlag E (September 2007). "Clinical, endocrinological, and epigenetic features of the 46,XX male syndrome, compared with 47,XXY Klinefelter patients". J. Clin. Endocrinol. Metab. 92 (9): 3458–65. PMID 17579198. doi:10.1210/jc.2007-0447. 
  4. ^ XX Male Syndrome
  5. ^ a b Lisker R, Flores F, Cobo A, Rojas FG (December 1970). "A case of XX male syndrome". J. Med. Genet. 7 (4): 394–398. PMC 1468937. PMID 5501706. doi:10.1136/jmg.7.4.394. 
  6. ^ Abusheikha N, Lass A, Brinsden P (2001). "Case Report: XX male without SRY gene and with infertility" (PDF). Human Reproduction 16 (4): 717–718. PMID 11278224. doi:10.1093/humrep/16.4.717.