IgM multiple myeloma: a diagnostic challenge in a patient with coexisting chronic lymphocytic leukaemia.

As IgM multiple myeloma is a rare poorly characterised disease entity; there is only limited published data on its clinical, microscopic and immunophenotypic features. We report a 72-year-old man misdiagnosed as Waldenström's macroglobulinemia. Also the diagnosis was further complicated by coexisting chronic lymphocytic leukaemia. Following confirmation of IgM myeloma, in view of the patient's deteriorating clinical condition; he was entered into the UK Medical Research Council Myeloma IX trial where he had partial response to chemotherapy. This case highlights the value of detailed immunophenotypic evaluation when clinical and morphological markers are equivocal.