RESUMO
IgM multiple myeloma (MM) is a rare entity representing approximately 0.5% of all MM. It should be distinguished from malignant neoplasms of B cells with plasmacytic differentiation such as Waldenstrom macroglobulinemia (WM) and marginal zone lymphoma with plasmacytic differentiation. Plasma cell leukemia (PCL) is a rare and aggressive variant of MM characterized by the presence of circulating plasma cells. We present a case report of a patient who presented with IgM MM in primary PCL phase with high-risk cytogenetics. To our knowledge, this is the first reported case of IgM MM with primarily leukemic presentation in the era of novel drugs. We demonstrate that it is important to distinguish IgM MM from WM and review the data from clinical trials that was used to devise a treatment strategy for this high-risk patient. This case adds to the understanding of the diagnosis and management of IgM MM in leukemic phase.