Bovine like-sexed male twins with chromosomal chimerism.

Sex-chromosomal chimerism (XX/XY) was described in a pair of bovine like-sexed male twins. One of the twins showed malformed external genitalia, and the other was phenotypically normal. It is proposed that sex-chromosomal chimerism is associated with a choriovascular anastomosis between like-sexed twins examined and "female fetus" which may be overlooked at parturition.