XX male syndrome, also known as
De la Chapelle syndrome, is a rare congenital
intersex condition where an individual with a female
genotype has
phenotypically male characteristics that can vary among cases. In 90 percent of these individuals, the syndrome is caused by the
Y chromosome's
SRY gene, which triggers male reproductive development, being accidentally 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 through various detection methods and occurs in approximately 1:20,000 newborn males, making it much less common than
Klinefelter syndrome. Treatment is medically unnecessary, although some individuals choose to undergo treatments to make them appear more male or female.
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