[Granulocyte-colony stimulating factor-producing myeloma with clinical manifestations mimicking chronic neutrophilic leukemia].

A 68-year-old man was diagnosed as having bronchial asthma in November 1996. He presented with leukocytosis in June 2002. The WBC count was 29,900/microliter with 82% mature neutrophils showing toxic granules. The neutrophil alkaline phosphatase score and serum level of vitamin B12 were elevated. Bone marrow demonstrated myeloid hyperplasia and plasmacytosis. Cytogenetic and molecular analyses were negative for Philadelphia chromosome and BCR/ABL fusion gene. Lambda-type Bence-Jones protein was detected on the serum and urinary immunoelectrophoresis. The coexistence of chronic neutrophilic leukemia and myeloma was suspected based on the clinical features. The serum level of granulocyte-colony stimulating factor (G-CSF) was elevated. Immunohistochemically, atypical plasma cells were positive for anti G-CSF antibody. Finally, we diagnosed this patient as having a G-CSF-producing myeloma. Treatment with melphalan and prednisolone was initiated without beneficial response. He was then admitted to our hospital for ROAD therapy (ranimustine, vincristine, melphalan, and dexamethasone). The neutrophil count decreased in parallel with the serum G-CSF level. These observations indicated that the neutrophilia in this case was probably caused by a reactive response to G-CSF secreted from the myeloma cells.