Disputed Maternity Leading to Identification of Tetragametic Chimerism

Chimerism is the presence of two genetically distinct cell lines in an organism. This report describes a phenotypically normal woman who was found to have tetragametic chimerism after histocompatibility testing of family members suggested that she was not the biologic mother of two of her three children. She had only one cell line in peripheral blood but had more than one in other tissues. Her T lymphocytes showed full tolerance of cells from family members with any combination of four familial HLA haplotypes. Chimerism, the presence of two genetically distinct cell lines in an organism, either is acquired through the infusion of allogeneic hematopoietic cells during transplantation 1 or transfusion 2 or is inherited. In fraternal twins, chimerism occurs by means of blood-vessel anastomoses. A less common cause of congenital chimerism — so-called tetragametic chimerism — occurs through the fertilization of two ova by two spermatozoa, followed by the fusion of the zygotes and the development of an organism with intermingled cell lines. 3 Examples have been found in mice 4 and other mammalian species, 5 – 7 including humans. 8 – 17 Affected persons are identified by the finding of . . .