The Myelodysplastic Syndromes.

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by peripheral blood cytopenias with a hypercellular bone marrow exhibiting dyspoiesis. The MDS range from those with a relatively indolent course (e.g., refractory anemia with or without ringed sideroblasts) to more aggressive disorders (e.g., refractory anemia with excess blasts [RAEB], and RAEB in transformation [RAEB-T]), which may exhibit a clinical course indistinguishable from acute myeloid leukemia (AML). Supportive care is the standard treatment for most patients, particularly those who are elderly, with the judicious use of blood components and antibiotics. For younger patients with RAEB and RAEB-T, antileukemic therapy might be considered, since the outcome is similar to that of patients with AML. Promising new chemotherapy agents currently in clinical trials include the topoisomerase I inhibitor, topotecan. The only curative treatment for MDS is allogeneic bone marrow transplantation, with long-term survival in approximately 40%, but with treatment-related deaths in 25%-40%. Factors predicting outcome include age, cytogenetics, number of blasts, and others. Myeloid growth factors (e.g., G-CSG, GM-CSF), increase the granulocyte count in most patients and may be useful in the setting of an active infection, although the prophylactic use of these agents does not improve survival. Erythropoietin increases the hematocrit in about 20% of patients. Growth factors being evaluated for their role in enhancing platelet counts include interleukin 11, stem cell factor, and megakaryocyte growth and development factor (thrombopoietin). Newer strategies to improve the outcome of patients with MDS should be based on an increased understanding of the biology of these disorders.