title: Unusual XX/XY chimerism.
abstract: Apparently identical twin boys are both XX/XY and have two populations, A1 and B, of cells in their peripheral blood. Chimerism in somatic tissue outside the blood cells can be demonstrated in only one of the twins. From analysis of chromosomes and many gene markers the mechanism of origin of the unusual twins remains unclear.
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics; D002675:Child, Preschool; D002678:Chimera; D005260:Female; D006680:HLA Antigens; D006801:Humans; D008297:Male; D011247:Pregnancy; D012730:Sex Chromosomes; D014166:Transferases / Q000097:blood; D014427:Twins
chemical_list: D000017:ABO Blood-Group System; D006680:HLA Antigens; D014166:Transferases