title: Refractory anemia with ring sideroblasts and RARS with thrombocytosis.
abstract: BACKGROUND
  Ring sideroblasts (RS) are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. Two myeloid neoplasms defined by the presence of RS, include refractory anemia with ring sideroblasts (RARS) and RARS with thrombocytosis (RARS-T).
  
  
  METHODS
  RARS is a lower risk myelodysplastic syndrome (MDS) with dysplasia limited to the erythroid lineage, <5% bone marrow (BM) blasts and ≥15% BM RS. RARS-T is a provisional entity in the MDS/MPN (myeloproliferative neoplasm) overlap syndromes, with diagnostic features of RARS, along with a platelet count ≥450 × 10(9)/L and large atypical megakaryocytes similar to those observed in BCR-ABL1 negative MPN. Mutations and Karyotype: Mutations in the SF3B1 gene are seen in ≥80% of patients with RARS and RARS-T, and strongly correlate with the presence of BM RS; RARS-T patients have additional mutations such as, JAK2V617F (∼60%), MPL (<5%), and CALR (<5%). Cytogenetic abnormalities are uncommon in both RARS and RARS-T.
  
  
  METHODS
  Most patients with RARS are stratified into lower risk groups by the International Prognostic Scoring System (IPSS) for MDS and the revised IPSS. Disease outcome in RARS-T is better than that of RARS, but worse than that of essential thrombocytosis. Both RARS and RARS-T have a low risk of leukemic transformation.
  
  
  METHODS
  Anemia and iron overload are complications in both diseases and are managed similar to lower risk MDS. Aspirin therapy is reasonable in RARS-T, especially in the presence of JAK2V617F, but the value of platelet-lowering drugs is uncertain. Case reports of RARS-T therapy with lenalidomide warrant additional studies.
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Mrinal M
authors.initials: MM
authors.lastname: Patnaik
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ayalew
authors.initials: A
authors.lastname: Tefferi
mesh_terms: D000753:Anemia, Refractory / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D000756:Anemia, Sideroblastic / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D020533:Angiogenesis Inhibitors / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use; D005260:Female; D006801:Humans; D019190:Iron Overload / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D053614:Janus Kinase 2 / Q000235:genetics; D000077269:Lenalidomide; D008297:Male; D009154:Mutation; D009190:Myelodysplastic Syndromes / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D010750:Phosphoproteins / Q000235:genetics; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use; D000072260:RNA Splicing Factors; D053628:Receptors, Thrombopoietin / Q000235:genetics; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics; D012307:Risk Factors; D013792:Thalidomide / Q000031:analogs & derivatives / Q000627:therapeutic use; D013922:Thrombocytosis / Q000188:drug therapy / Q000235:genetics / Q000473:pathology
chemical_list: D020533:Angiogenesis Inhibitors; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D000072260:RNA Splicing Factors; D053628:Receptors, Thrombopoietin; D017413:Ribonucleoprotein, U2 Small Nuclear; C112491:SF3B1 protein, human; C082218:MPL protein, human; D013792:Thalidomide; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D000077269:Lenalidomide; D001241:Aspirin