Simultaneous occurrence of acute myelogenous leukaemia and multiple myeloma without previous chemotherapy.

A patient with simultaneous occurrence of multiple myeloma and acute myelogenous leukaemia without previous chemotherapy was studied. Indirect immunofluorescence and protein A-coupled ox red blood cells rosette technique by use of anti-idiotype (Id) antibody showed some T cells with receptors of idiotypic specificity identical with that of the secreted myeloma protein. Plaque forming cell assay showed the presence of Id producing peripheral blood lymphocytes with EB virus receptor, probably B cells. These observations strongly suggest that multiple myeloma was not the result of a neoplastic transformation of the most differentiated B cells, plasma cell, but of lymphoid stem cells capable of differentiating to either B or T cells. However, there was not a detectable population of myeloblasts that expressed the same idiotype. Chromosomal analysis revealed a deletion of the long arm of chromosome 8 in myeloblasts but not in T or B cells. These results support the hypothesis of separate clonal origins for the leukaemic and myeloma components in this case.