Leukaemoid monocytosis in M4 AML following chemotherapy and G-CSF.

We describe a patient with M4 AML treated with standard chemotherapy followed by G-CSF who developed marked monocytosis on day 8 of G-CSF therapy. Fourteen days after discontinuation of G-CSF therapy his monocyte counts returned to normal levels and a marrow aspirate showed a reduction in blast cells. He received further chemotherapy without G-CSF and without any recurrence of the raised leucocyte count but failed to achieve full remission. Although this G-CSF-driven leucocytosis was alarming it did not appear to have adversely affected the patient's prognosis.