Two M-components in a single cell lineage in a patient with a dual isotype secretory B-cell tumour

Abstract

We describe a case of Waldenstrom's macroglobulinaemia with two M- components (IgM and IgG) with the same λ light chain. Southern blot analysis of bone marrow cells showed rearrangements of immunoglobulin heavy and λ light chain genes. Sequencing of the complementarity determining region 3 of the two γ and μ transcripts showed 100% homology. Immunofluorescence study showed that most cells stained for both IgG and IgM. These findings indicated that a single population of cells was expressing two isotypic variants of IgG and IgM, as the genes responsible for production of both components had the same origin.