SF3B1 mutations are frequent in patients with refractory anemia with ringed sideroblasts (RARS), with myelodysplastic/myeloproliferative neoplasms with ringed sideroblasts and thrombocytosis (RARS-T), and also in up to 14% PMF patients (73–76). The gene discussed is SF3B1; the disease is myelodysplastic syndrome with ring sideroblasts.