XX male syndrome

Overview
XX male syndrome (also called de la Chapelle syndrome, for a researcher who characterized it in 1972 ) is a rare sex chromosomal disorder. Usually it is caused by unequal crossing over between X and Y chromosomes during meiosis.

It is less common than Klinefelter syndrome.

Presentation
Symptoms include small testes, gynecomastia and sterility. Many individuals with this condition also have effeminate characteristics.

Pathophysiology
Men typically have one X chromosome and one Y chromosome in each diploid cell of their bodies. Women typically have two X chromosomes.

So-called XX males have two X chromosomes; thus they are genetically female but otherwise appear to be male.