We describe here a 64-year-old woman who simultaneously presented with chronic neutrophilic leukemia (CNL) and multiple myeloma (MM). The patient presented with mature neutrophilic leukocytosis, hepatosplenomegaly, the absence of Philadelphia chromosome and the BCR-ABL fusion gene, along with IgG kappa type monoclonal gammopathy in her serum and urine. The bone marrow aspirates showed hypercellularity with marked granulocytic hyperplasia and an increase in immature plasma cells. The neutrophil function tests showed increased phagocytosis, chemotaxis and respiratory burst activity, but there was normal microbial killing activity. The patient was treated with dexamethasone and pamidronate for MM and with hydroxyurea for CNL, and she was discharged from the hospital in an improved condition.

Keywords: Chronic neutrophilic leukemia, Multiple myeloma, Neutrophil function test