Morphologic changes of neutrophils in myelodysplastic syndrome treated with recombinant human granulocyte colony-stimulating factor.

Two cases of myelodysplastic syndrome (MDS) were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF). In both cases, an increase of peripheral neutrophil counts was noted with a peak within 12 hr after the rhG-CSF administration. Neutrophils with ring shaped or hypersegmented nuclei were noted in the peripheral blood during the treatment, and they disappeared promptly after discontinuation of the therapy. The results indicate that the rhG-CSF might have mobilizing and differentiating effects on neutrophils derived from the MDS clone.