A case of monoclonal gammopathy associated with acute myelomonocytic leukemia with eosinophilia suggested to be the result of lineage infidelity

Acute myelomonocytic leukemia (AMMoL) accompanied by monoclonal gammopathy is a rare condition, and its pathogenesis and the cytogenetic mechanism of such leukemogenesis have not been determined in detail. A case of AMMoL wit h eosinophilia accompanied by immunoglobulin G kappa monoclonal gammopathy is described. Immunophenotypic studies of the peripheral blood and bone mar row mononuclear cells revealed no evidence of abnormally proliferating cell s of B-lineage. DNA analyses of bone marrow mononuclear cells containing le ukemic cells revealed rearrangement of the kappa-light chain (Ig kappa) gen e end c-myc and c-jun proto-oncogenes. The intensities of the rearranged ba nds for these genes on Southern blot analysis suggested the existence of a major population of leukemic cells with rearranged Ig kappa gene and minor population(s) of leukemic cells with rearranged c-myc and/or c-jun proto-on cogene(s) in the patient's bone marrow and indicated the occurrence of gene tic evolutionary changes in leukemic cells in this patient before starting chemotherapy, These results suggest that these leukemic cells are the most likely candidate for immunoglobulin G kappa monoclonal protein production, and structural abnormalities of c-myc and c-jun proto-oncogenes may have co ntributed to the evolution of leukemic cells in this patient. (C) 2000 Wile y-Liss, Inc.