A case of IgD myeloma representing a missed biclonal paraproteinemia or isotype switch in a patient previously diagnosed with IgA–lambda myeloma

Multiple myeloma is a clonal plasma cell neoplasm that is identified in the laboratory by a presence of a monoclonal immunoglobulin or increased plasma light chain levels. The most commonly identified and tested immunoglobulins are IgA, IgG and IgM. Rare cases of multiple myeloma present with monoclonal IgD and IgE paraproteins. We present a case of IgD myeloma diagnosed in a patient who had achieved partial remission from a previously diagnosed IgA myeloma, possibly representing a missed biclonal paraproteinemia or isotype switch after treatment.