Acquired idiopathic sideroblastic anemia is one of a group of disorders known as the myelodysplastic syndromes (MDS) characterized by ineffective haemopoiesis affecting one or more blood cell lineages (myeloid, erythroid or megakaryocytic) leading to peripheral blood cytopenias and an increased risk of developing leukemia. Acquired idiopathic sideroblastic anemia is now more commonly referred to as refractory anemia with ringed sideroblasts or the acronym RARS.