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MDS Subtypes

There are several kinds (subtypes) of MDS. The subtype is determined from the results of the blood and bone marrow tests.

WHO Classification

The current WHO classification guidelines identify six subtypes.

  • MDS with single lineage dysplasia (MDS-SLD)
  • MDS with ring sideroblasts (MDS-RS)
    • Single lineage dysplasia (MDS-RS-SLD)
    • Multilineage dysplasia (MDS-RS-MLD)
  • MDS with multilineage dysplasia (MDS-MLD)
  • MDS with excess blasts (MDS-EB)
    • MDS with excess blasts-1 (MDS-EB-1)
    • MDS with excess blasts-2 (MDS-EB-2)
  • MDS with isolated del(5q)
  • MDS, unclassifiable (MDS-U)

The WHO classifies MDS into these subtypes based on how the cells within the bone marrow appear under a microscope as well as other factors. These include:

  • Number of dysplastic lineages: the number of types of blood cells (red blood cells, white blood cells, or platelets) that exhibit dysplasia
  • Cytopenias: how many low blood cell counts there are
  • Ring sideroblasts: what portion of immature red blood cells contain rings of iron deposits around the center
  • Blasts: the portion of immature forms of blood cells in the bone marrow and blood
  • Chromosome abnormalities: certain chromosome changes that are specific to MDS


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