XX male syndrome

Uncommon card · No. 87690

XX male syndrome, also known as de la Chapelle syndrome or 46,XX testicular disorder of sex development (or 46,XX DSD) is a rare condition in which an individual with a 46,XX karyotype develops a male phenotype. In 90 percent of these individuals, the syndrome is caused by the father's Y chromosome's SRY gene 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 genetic male. Less common are SRY-negative individuals, who appear to be XX genetic females, which is caused by a mutation in an autosomal or X chromosomal gene. Masculinization in those with the condition is variable, and those with the condition are sterile. This syndrome is diagnosed and occurs in approximately 1 in 20,000 newborn boys, making it much less common than Klinefelter syndrome. Medical...

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