Welcome to Managing MDS. I am Dr. Shyamala Navada and I am frequently asked what is refractory anemia with ring sideroblasts?
Refractory anemia with ring sideroblasts is one of the World Health Organization’s subtypes of MDS, most recently updated is MDS with ring sideroblasts. It constitutes between 3% to 11% of all MDS cases. Also abbreviated is RARS, it is a low-risk MDS characterized by anemia, dyserythropoiesis and the presence of 15% or more ring sideroblasts in the bone marrow nucleated red blood cells. Alternatively, one can have 5% or more ring sideroblasts in the presence of an SF3B1 mutation. Ring sideroblasts are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. The ring occurs as a result of the red blood cells being unable to process the iron that is used for making hemoglobin therefore causing it to build up and be deposited within the red blood cell. The presence of ring sideroblasts usually signifies ineffective erythropoiesis and mitochondrial iron overload. The presence of ring sideroblasts alone is not sufficient for a diagnosis of RARS. Complete evaluation of the non-erythroid lineages is necessary as well. MDS with ring sideroblasts includes subgroups with single lineage dysplasia and multi-lineage dysplasia. With patients with single lineage dysplasia, mutations in SF3B1 are seen in 80% or more of patients. In addition, myeloblasts account for fewer than 5% of nucleated bone marrow cells.
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