2 translocations, t(11;14) and t(1;6), in a patient with plasma cell leukaemia and 2 populations of plasma cells.

2 translocations, t(11;14) and t(1;6), were found in 24 out of 46 metaphases in bone marrow cells from an untreated patient with plasma cell leukaemia. The predominating cell population produced only kappa chains while a minute population produced IgG kappa. All serum Ig's were low and only minimal amounts of monoclonal IgG kappa were found in the serum and very small amounts of kappa light chains in the urine. Analyses of ours and 2 other reported patients indicated the possibility that the location of breakpoints on the chromosomes may be of etiologic importance for the type of light chain and perhaps for the class of heavy chain.