XX male syndrome, also known as de la Chapelle syndrome, is a rare intersex condition in which an individual with a 46,XX karyotype develops a male phenotype. Synonyms for XX male syndrome include 46,XX testicular difference of sex development (or 46,XX DSD)
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. 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. 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. Medical treatment of the condition varies, with medical treatment usually not necessary. The alternative name for XX male syndrome...
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