Statistical study on double paraproteinemias. Evidence for a common cellular origin of both myeloma globulins.

Double paraproteinemias (DPP) are usually considered as resulting from a proliferation of two independent clones of cells. The present study describes a statistical analysis based on 141 published cases of DPP. The incidence of the heavy chain classes as well as of light chain types association has been compared with the frequency of occurence of the same H and L chains in simple paraproteinemias. Computation of the frequency of associations showed that different heavy chains are randomly associated in DPP. However, light chains are more frequently of the same type in both immunoglobulins more so than could be expected on the basis of a biclonal hypothesis (p less than 0.005). This preferential occurence of identical light chains suggests a linkage in the synthesis of two proteins and it favours a monoclonal origin of myeloma cells in DPP.