The combined effects of all-trans retinoic acid and granulocyte colony-stimulating factor as a differentiation induction therapy for acute promyelocytic leukemia.

A 61-year-old male with acute promyelocytic leukemia (APL) had been in complete remission for the previous 15 months, but his APL relapsed with neutropenia. Although promyelocytes in bone marrow were reduced after administration of 60 mg all-trans retinoic acid (ATRA) daily, myelocytes were predominant on the myelogram and neutropenia did not recover. By adding 75 micrograms of granulocyte colony-stimulating factor (G-CSF) daily, neutrophils accounted for 35.0-55.5% of the myelogram, and the peripheral neutrophil count rose dramatically. Such morphological differentiation of myeloid series was also ascertained in terms of their functions of both neutrophil alkaline phosphatase activity and active oxygen producing capacity. This case supports the concept that G-CSF accelerates ATRA-induced neutrophilic differentiation of blast cells in APL.