Skip to Main Content

In contrast to florid (polyblastic) acute myelogenous leukemia (AML), the myelodysplastic syndrome (MDS) encompasses a group of neoplastic (clonal) myeloid disorders that range from nonprogressive to more slowly progressive than AML. The disorders may appear uncommonly in childhood or young adulthood, especially after cytotoxic therapy for another cancer, but the incidence increases exponentially after age 40 years. The disorders also may develop as a result of inherited syndromes that predispose to MDS or AML, such as Fanconi anemia. Most cases occur between the ages of 50 and 90 years. Cases usually occur de novo, but a proportion result from hematopoietic cell injury during treatment of lymphomas or solid tumors with cytotoxic therapy. The disorders range from clonally derived (refractory) anemias to oligoblastic myelogenous leukemia (refractory anemia with excess blasts). The diseases share a propensity to the development of (1) cytopenias, as a result of exaggerated apoptosis of late-stage marrow precursor cells, and (2) multilineage dysmorphogenesis of blood cells. Red cells often have readily discernible poikilocytosis, anisocytosis, anisochromia, and basophilic stippling. The marrow usually contains increased erythroid precursors with dysmorphic features, including nuclear distortions and scanty, poorly hemoglobinized cytoplasm or macroerythroblasts. Ringed sideroblasts are a frequent feature. Neutrophils have anomalies, including bilobed or hypersegmented nuclei and hypogranulated cytoplasm, in association with increased marrow granulocyte precursors. Giant and microcytic platelets, sometimes with abnormal or absent granulation, in the blood are associated with megakaryocytic hyperplasia and atypical lobulation of the nucleus and decreased marrow megakaryocyte size. In the nonprogressive syndromes, anemia may be accompanied by mild variations in other cell counts, usually decreases in neutrophil and platelet levels, and blast cells are not increased in the marrow (<2%). Clonal cytogenetic abnormalities occur in approximately 50 percent of patients. Chromosomes 5, 7, and 8 are most frequently involved. The classic 5q– syndrome is categorized within the myelodysplastic disorders. The syndrome primarily affects older women, and features anemia and hypercellular and dysmorphic erythropoiesis with lobulated erythroblast nuclei and hypolobulated micromegakaryocyte nuclei, but usually normal or elevated platelet counts. It is the most indolent form of the myelodysplastic syndromes with the lowest propensity to evolve into AML. In the more progressive syndromes, leukemic blast cells are increased, cytopenias are more severe, and the disease has high morbidity and mortality from infection and bleeding. Each of the syndromes has a propensity to evolve into polyblastic AML, ranging from approximately 10 to 15 percent in the clonal (refractory) anemia to approximately 40 percent of patients with trilineage cytopenias and increased marrow blast cells. Mortality from infection is a risk in patients with severe neutropenia. Various scoring systems have been developed to help predict outcome and the timing of various treatments. In the most indolent forms, therapy may not be required. Erythropoietin plus granulocyte colony-stimulating factor may improve the anemia or decrease transfusion requirements, if clonal anemia is the principal feature. Cyclosporine or antithymocyte globulin may transiently improve the anemia in patients with clonal anemia, hypoplastic marrows, and low blast counts. Therapy with cytotoxic drugs, ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.