According to 2017 WHO classification, MDS-RS is an MDS characterized by cytopenias, usually anemia, morphological dysplasia involving one or more myeloid lineages and ring sideroblasts representing ≥15% of the bone marrow erythroid precursors (or 5% in the presence of SF3B1 mutations). The gene discussed is SF3B1; the disease is myelodysplastic syndrome.