Myelodysplastic syndrome (MDS) is a clonal disorder characterized by ineffective hematopoiesis and variable cytopenias with a considerable risk of progression to acute myeloid leukemia. Epidemiological assessment of MDS remains challenging because of evolving classification systems, but the overall incidence in the United States is estimated to be approximately 4 per 100,000 and increases with age. The sequential accumulation of mutations drives disease evolution from asymptomatic clonal hematopoiesis (CH) to CH of indeterminate potential, clonal cytopenia of unknown significance, to frank MDS. The molecular heterogeneity seen in MDS is highly complex and includes mutations of genes involved in splicing machinery, epigenetic regulation, differentiation, and cell signaling. Recent advances in the understanding of the molecular landscape of MDS have led to the development of improved risk assessment tools and novel therapies. Therapies targeting the underlying pathophysiology will hopefully further expand the armamentarium of MDS therapeutics, bringing us closer to a more individualized therapeutic approach based on the unique molecular profile of each patient and eventually improving the outcomes of patients with MDS. We review the epidemiology of MDS and the newly described MDS precursor conditions CH, CH of indeterminate potential, and CCUS. We then discuss central aspects of MDS pathophysiology and outline specific strategies targeting hallmarks of MDS pathophysiology, including ongoing clinical trials examining the efficacy of these therapeutic modalities.
