Blood group chimaerism: a possible further example.

A blood group chimaera is described whose red blood cells exhibit a dual population of group A1 and O, in the proportions 20% and 80% respectively. These results could also indicate a blood group mosaic of the Amos type, but family studies, secretor and transferase investigations on this patient suggest that blood group chimaerism of unestablished type is more likely. There was no further evidence of chimaerism found during cytogenetic investigations, immunoglobulin allotyping or studies of red cell enzyme systems. Blood group chimaeras were previously thought to be rare, as dual red cell populations and the resulting mixed-field agglutination patterns are not always easy to recognise. This case is the second example of chimaerism found within two years in a single routine laboratory, appearing to confirm the view that chimaerism is not as uncommon as previously thought.