A case of multiple myeloma producing granulocyte colony-stimulating factor.

A case of multiple myeloma (IgA-lambda) with marked granulocytosis, which measured up to 9.9 x 10(4)/mm3, is described. Matured neutrophils were predominant and blasts were not found in the peripheral blood. The serum granulocyte colony-stimulating factor (G-CSF) was notably elevated. The disease ran a chronic course and granulocytosis and elevated serum G-CSF continued. The patient developed atelectasis and bronchopneumonia, and died of respiratory failure. At autopsy, bone marrow showed marked myeloid hyperplasia in varying states of differentiation. The enlarged spleen also disclosed numerous myeloid cells of varying differentiation. Small aggregations of atypical plasma cells were present in the marrow and spleen. Immunohistochemically, atypical plasma cells were positive for anti-G-CSF antibody, which indicated G-CSF secretion from the myeloma cells. To our knowledge, this is the first reported case of G-CSF-producing multiple myeloma.