The Premyelodysplastic State and the Secondary Hematologic Disorders

The secondary hematologic disorders consist of the progressive appearance of increasingly abnormal marrow cell populations with increasingly abnormal hemopoiesis culminating in the appearance of secondary acute myelogenous leukemia. At the biological level the secondary hematologic disorders result from the accumulation of molecular genetic lesions which confer a proliferative advantage on a stem cell and its progeny which in turn results in the successive overgrowth of increasingly abnormal monoclonal cell populations. We have identified 4 of 15 female patients cured of lymphoma by intensive cytotoxic therapy as having monoclonal hemopoiesis. Despite the presence of normal peripheral blood counts, the bone marrows of the 3 patients who were studied intensively manifested evidence of grossly abnormal hemopoiesis. We have named this state of normal blood counts in combination with monoclonal hemopoiesis in patients previously exposed to hemopoietic toxins “preMDS.” This “preMDS” state either represents an earlier stage of the secondary hematologic disorders or represents a transient preclinical manifestation of myelodysplasia. Longitudinal patient follow up is needed to distinguish between these two possibilities.