How are refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) characterized in the French-American-British (FAB) classifications of myelodysplastic syndrome (MDS)?

Updated: Jul 24, 2018
  • Author: Emmanuel C Besa, MD; Chief Editor: Koyamangalath Krishnan, MD, FRCP, FACP  more...
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RA and RARS are characterized by 5% or less myeloblasts in bone marrow. RARS is defined morphologically as having 15% erythroid cells with abnormal ringed sideroblasts (see the image below), reflecting an abnormal accumulation of iron in the mitochondria. Both RA and RARS have a prolonged clinical course and a low prevalence of progression to acute leukemia. In a review of United Kingdom population-based data, with followup of 2 to 11 years, progression to acute leukemia occurred in 5% of RARS cases, compared with 25% of RAEB cases. [13]

Bone marrow film (1000× magnification) demonstrati Bone marrow film (1000× magnification) demonstrating ring sideroblasts in Prussian blue staining in a refractory anemia with excess of blasts in transformation. Courtesy of U. Woermann, MD, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland.

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