All-trans-retinoic acid induced enrichment of functionally normal neutrophils in vivo in a patient with acute promyelocytic leukemia.

A patient with resistant acute promyelocytic leukemia was treated with all-trans-retinoic acid (45 mg/m2 per day for 42 days) and obtained complete remission at day 14. Analysis of the neutrophils from the patient at day 7 demonstrated that they were indistinguishable from neutrophils from normal individuals as far as this is assessed by presently available functional tests. Furthermore, the degree of peroxidase positivity of neutrophils obtained from the patient was similar to control values. Thus, taken together with the hematologic features, all-trans-retinoic acid induces leukemic promyelocytes to become functionally normal neutrophils. This therapy is particularly suitable in obtaining complete remission in patients with acute promyelocytic leukemia with neutropenia with or without previous chemotherapy.