The myelodysplastic syndromes are neoplasms of hematopoietic progenitor cells characterized by ineffective hematopoiesis and increased risk of transformation to AML. Clinically, patients develop symptoms related to with cytopenias, typically progressive anemia with or without thrombocytopenia or neutropenia that is unrelated to a defined reversible cause such as nutritional deficiency. Histologically, MDS is suggested by the presence of dysplasia in >10% of cells in one or more myeloid lineage on bone marrow evaluation. Characteristic cytogenetic abnormalities also aid in making the diagnosis of MDS.