PLASMACYTOSIS IN ACUTE MYELOID-LEUKEMIA - 2 CASES OF PLASMACYTOSIS AND INCREASED IL-6 PRODUCTION IN THE AML BLAST CELLS

An increased plasma cell count in the bone marrow occurs in a subgroup of patients with acute myeloid leukemia (AML), The pathogenic mechani sm for this plasmacytosis is unclear. In this report we describe two p atients with AML and plasmacytosis who shared some features of their d iseases. The morphological subtypes were AML M4 and M4eo; the leukemia s were secondary to cytotoxic pretreatment, and complex cytogenetic ch anges were found in the leukemic cells of both patients. There was a m arked increase in the number of bone marrow plasma cells in both cases and no monoclonal immunoglobulin was detectable. The IgH-CDR3 gene sc an depicted a monoclonal IgH rearrange ment in the bone marrow cells o f one patient. Analysis of the cytokine production of the leukemic cel ls showed a high production of IL-6 of the leukemic blast cells in the in vitro cell culture and a high cytoplasmic IL-6 in the leukemic cel ls as revealed by immunocytology, We describe the clinical picture of a type of secondary AML with FAB M4 morphology associated with bone ma rrow plasmacytosis. We suggest that paracrine growth stimulation of pl asma cells by paraneoplastic IL-6 production of the leukemic blast cel ls contributes to the plasmacytosis observed in patients with AML.