Girl, 46XY, puts CBX2 before SRY

A baby was tested before birth to check for genetic conditions and was found to be 46XY – male. When born, the baby was a girl, and checks found a uterus and ovaries that appear to be normal.

In mice there is a similar situation causing male-to-female sex reversal, in which the mice are sterile.

Working back from known results in mice to humans, this suggests that mutations in Chromobox homolg 2 (CBX2) on chromosome 17 can shut off SRY, thus preventing the development of maleness.

It is too early to tell whether the girl, now age 7, will be sterile.

Published in American Journal of Human Genetics. March 2009.