[Marked dysmyelopoiesis after induction chemotherapy in a case of acute myelomonocytic leukemia (M 4) with t(6; 11)].

A case of AML (M 4) with t(6; 11) showed recovery to myelodysplastic syndrome (MDS)-like bone marrow after one course of DCMP regimen. Dysplastic changes of three cell-lineages were observed and micromegakaryocytes were markedly increased in number. Recovering hematopoiesis was incomplete. During MDS-like phase, t(6; 11) disappeared, reverting to normal karyotypes. Low dose ara-C regimen did not show any effect. AML soon relapsed with reappearance of t(6; 11). MDS-like abnormal hematopoiesis has recently been reported to occur after remission induction therapy or at the time of relapse. G-6PD isozyme study revealed in a remission case of AML that hematopoiesis still consisted of abnormal clone in spite of karyotypic normalization. The abnormal hematopoiesis observed in our case can be referred to such a clonal disorder predominating after disappearance of blastic component of AML. It seems important to reveal what proportion of de novo AMLs shows such an abnormal hematopoiesis and to establish suitable therapeutic approach.