Refractory anemia with excess blasts (RAEB) describes refractory anemia with blast counts in the marrow over the 5-19% range. This is subclassified into 2 subtypes based on blast count and other findings.


NOTE: In the WHO classification, a blast count >= 20% indicates acute leukemia.


General features:

(1) blast count in the bone marrow from 5 to 19%

(2) usually in patients > 50 years of age

(3) usually multilineage dysplasia in the bone marrow



(1) RAEB-1

(2) RAEB-2


Features of RAEB-1 includes ALL of the following:

(1) 5-9% blasts in bone marrow

(2) < 5% blasts in the peripheral blood

(3) Auer rods absent


Features of RAEB-2 includes any of the following:

(1) 10-19% blasts in the bone marrow

(2) 5-9% blasts in bone marrow with 5-19% blasts in the peripheral blood

(3) presence of Auer rods



• Patients usually have progressive cytopenias associated with marrow failure.

• About 25% of RAEB-1 and 33% of RAEB-2 patients progress to AML.


Median Survival


18 months


10 months


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