XX male syndrome, also known as de la Chapelle syndrome, is a rare congenital intersex condition in which an individual with a 46, XX karyotype (otherwise associated with females) has phenotypically male characteristics that can vary among cases. Synonyms include 46,XX testicular difference of sex development (46,XX DSD), 46,XX sex reversal, nonsyndromic 46,XX testicular DSD, and XX sex reversal.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. [Source: Wikipedia ]