An unusual observation of tetragametic chimerism: forensic aspects.

A 41-year-old healthy Caucasian male showed an unidentifiable direct AB0 group and a B group by an indirect method revealing the presence of natural antibodies anti-A1 and anti-A2. Mixed fields with anti-B and anti-A+B antisera led to the conclusion that blood group B and 0 cell populations were present in a 1:1 ratio. A negative anamnesis for both transplantation and transfusion suggested a chimerism. DNA analysis of tissues revealed a tetragametic chimerism due to an apparent double parental contribution of nuclei in a phenotypically normal man.