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WHO classification 2008 of myelodysplastic syndromes

1 Bicytopenia may occasionally be observed. Cases with pancytopenia should be classified as MDS-U

2 If the marrow myeloblast percentage is <5% but there are 2-4% myeloblasts in the blood, the diagnostic classification is RAEB-1. If the marrow myeloblast percentage is <5% and there are 1% myeloblasts in the blood, the case should be classified as MDS-U.

3 Cases with Auer rods and <5% myeloblasts in the blood and <10% in the marrow should be classified as RAEB-2

DiseaseBlood findingsBone marrow findings

Refractory cytopenias with unilineage dysplasia (RCUD)

Refractory anaemia (RA)

Refractory neutropenia (RN)

Refractory thrombocytopenia (RT)

Unicytopenia or bicytopenia1

Rare blasts or none (<1%)

Unilineage dysplasia

≥ 10% of the cells of the affected lineage are dysplastic

<5% blasts

<15% of the erythroid precursors are ring sideroblasts

Refractory anaemia with ring sideroblasts (RARS)

Anemia

No blasts

Erythroid dysplasia only

≥ 15% of erythroid precursors are ring sideroblasts

Refractory cytopenia with multilineage dysplasia (RCMD)

Cytopenia(s)

Rare blasts or none (<1%) 2

No Auer rods

<1x109/L monocytes

Dysplasia in ≥ 10% of cells in two or more myeloid lineages (neutrophil and/or erythroid precursors and/or megakaryocytes)

<5% blasts

No Auer rods

±15% ring sideroblasts

Refractory anaemia with excess blasts-1 (RAEB-1)

Cytopenia(s)

<5% blasts

No Auer rods

<1x109/L monocytes

Unilineage or multilineage dysplasia

5-9% blasts 2

No Auer rods

Refractory anaemia with excess blasts-2 (RAEB-2)

Cytopenia(s)

5-19% blasts

Auer rods ± 3

<1x109/L monocytes

Unilineage or multilineage dysplasia

10-19% blasts

Auer rods ±

Myelodysplastic syndrome – unclassified (MDS-U)

Cytopenia(s)

≤ 1% blasts 2

Unequivocal dysplasia in less than 10% of cells in one or more myeloid cell lines

<5% blasts 2

MDS associated with isolated del(5q)

Anaemia

Usually normal or increased platelet count

Rare blasts or none (<1%)

Normal to increased megakaryocytes with hypolobated nuclei

<5% blasts 2

Isolated del(5q) cytogenetic abnormality

No Auer rods