Transient expression of a second monoclonal component in two forms of biclonal gammopathy

Two cases of transient biclonal gammopathy are described, one having an IgG kappa and an IgA kappa monoclonal component and another with IgG1 kappa and IgG4 kappa monoclonal components. In both of these cases the second monoclonal component gradually disappeared. Anti-idiotypic antibodies were made against the major monoclonal serum component; in the first case the idiotype of the IgG kappa clone was not found in the IgA kappa plasma cells (real biclonal gammopathy) whereas in the second case the idiotypes of the two clones were identical (apparent biclonal gammopathy). The evolution to monoclonal gammopathy is discussed with regard to the existence of common malignant precursor cells in biclonal gammopathy.