Two populations of Rh groups together with chromosomally abnormal cell lines in the bone marrow.

At the onset of his disease a man with polycythaemia vera had chromosomally normal cells in the bone marrow and Rh blood group CDe/cDE. Five years later he developed pancytopenia with erythroid hyperplasia of the bone marrow. This was associated with the presence of a major abnormal clone, 45,XY,B-,C-,16+, a minor clone, 45,XY,2+,3-,C-, and a few apparently normal cells. At the same time Rh blood grouping showed two populations of red cells, one CDe/cDE and one giving the reactions of CDe/CDe which can be interpreted as CDe. If monosomic CDe be the correct interpretation the case provides a strong hint that the Rh complex locus is sited either on the long arm of a B-group chromosome or, less probably, on an autosome of the C group.