The myelodysplastic syndrome (MDS) is a heterogeneous group of clonal neoplastic stem cell disorders. The disease is characterized clinically by bone marrow failure with peripheral cytopenias and a tendency to progress to acute myeloid leukemia (AML). Pathologically, dysplastic morphologic features in the peripheral blood and bone marrow gives the disease its misnomer as myelodysplastic syndrome, although it is truely neoplastic.1

The recognition and classification of MDS have evolved over the years as we learn more about the disease. The description of refractory anemia early in the past century was followed by the observation of progression to leukemia. MDS was then recognized as a primary bone marrow failure disorder. The French-American-British classification (FAB) and its revision addressed the heterogeneity in the subtypes and noted the variability in progression to AML.23 The new World Health Organization (WHO) classification refined the FAB classification in an attempt to better predict outcome by using more homogenous and distinct subgroups.4

MDS is predominantly a disease of the older adults, probably reflecting the requirement of multiple and prolonged leukemogens for the disease to develop. MDS may be more common than chronic lymphocytic leukemia (CLL). The estimated incidence is 4/100,000 US citizens per year and it increases with age.5 Majority of patients will succumb to the disease, more so because of infections and their complications rather than AML evolution.6 Only one third of patients will eventually progress to AML, a process that may result from accumulating further DNA damage, as well as from clonal evolution.

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