This document provides an overview of myelodysplastic syndrome (MDS). It discusses the history and evolving definitions of MDS. Key points include that MDS is a heterogeneous group of stem cell disorders characterized by cytopenias, dysplasia, and risk of acute myeloid leukemia. The document reviews classification systems including FAB and WHO criteria. It covers pathogenesis, clinical features, risk factors, diagnostic evaluation including blood and bone marrow findings, and molecular abnormalities associated with MDS.