[Granulocyte-colony stimulating factor-producing multiple myeloma presenting with neutrophilia].

A 71-year-old woman complained of nausea and anorexia. Laboratory tests revealed significant neutrophilia and immunoglobulin A-kappa type M proteinemia, as well as increased plasma cells on bone marrow examination. Furthermore, the serum granulocyte-colony stimulating factor (G-CSF) concentration was high at 160 pg/ml, and the colony stimulating factor 3 receptor (CSF3R)-T618I mutation was negative. Immunohistochemical (IHC) analysis of bone marrow specimens using the anti-G-CSF antibody revealed immunopositivity of some myeloma cells. The patient was diagnosed using G-CSF-producing myeloma and was treated with daratumumab, lenalidomide, and dexamethasone. Her treatment resulted in a very good partial response, with normalization of both serum G-CSF levels and neutrophil count. There have been a few cases of G-CSF -producing myeloma reported, and it has previously been reported as chronic neutrophilic leukemia with M proteinemia. According to previous reports, techniques such as serum G-CSF measurements, IHC with an anti-G-CSF antibody, and CSF3R gene mutation analysis are useful for differentiating G-CSF-producing myeloma. However, the clinical characteristics and long-term prognosis of G-CSF-producing myeloma remain unknown. Additional case gathering and investigations are required.