Refractory Anemia with Ring Sideroblasts

Definition

Myelodysplastic syndrome characterized by erythroid dysplasia with ring sideroblasts

Should be distinguished from RCUD because of longer median survival and lower rate of leukemic transformation
Exclusions
- Non-clonal causes for dysplasia must be excluded (see Differential Diagnosis)
- If chemotherapy or radiation therapy related, should be reported as "therapy-related myeloid neoplasm"
- <1 x 10³/μL monocytes (if present consider Chronic Myelomonocytic Leukemia)
- Lack of neutrophilia (if present consider BCR-ABL1+CML or atypical CML)
Refractory anemia - Hemoglobin <10 mg/dL
- Dysplasia limited to erythroid lineage (see below for criteria for dysplasia)
  - Must involve ≥10% of erythroids
  - If ≥10% of other lineage(s) involved see RCUD or RCMD
    - RCMD with ring sideroblasts is not distinct category in WHO 2008
      - Clinical course is similar to RCMD without ring sideroblasts

Ring sideroblasts (see definition below) ≥15% of total erythroid precursors (if <15% see RCUD)
If >450x10³/μL platelets in peripheral blood with marrow megakaryocytic proliferation, consider RARS-T
- This is a provisional mixed MDS/MPN entity that is commonly JAK2V617E mutated

Peripheral blood blasts <1%, based on 200 leukocyte differential
Bone marrow blasts <5%, based on 500 nucleated cell differential
Cytogenetics should be performed on every patient to verify the presence of a clonal abnormality
- Present in about 10% of patients
- If no clone present, patient must be observed for 6 months before diagnosis of MDS is given

Dita Gratzinger MD PhD
Tracy I George MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342