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Refractory Anemia with Excess Blasts (RAEB)

Last updated March 24, 2017

Refractory Anemia with Excess Blasts (RAEB)

Refractory Anemia with Excess Blasts (RAEB) is a type of bone marrow disorder, called myelodysplastic syndrome (MDS).


What are the other Names for this Condition? (Also known as/Synonyms)

  • RAEB (Refractory Anemia with Excess Blasts)

What is Refractory Anemia with Excess Blasts? (Definition/Background Information)

  • Refractory Anemia with Excess Blasts (RAEB) is a type of bone marrow disorder, called myelodysplastic syndrome (MDS)
  • Myelodysplastic syndromes exhibit disordered (dysplastic) development of all non-lymphocyte blood cells (myeloid cells). MDS is caused by various abnormalities of the bone marrow
  • Bone marrow is the spongy tissue found inside the bones. Normally, it is the main site of blood cell production (hematopoiesis). The blood cells include:
    • Red blood cells (erythrocytes), which transport ‘gases’, such as oxygen
    • White blood cells (leukocytes), important to the immune system
    • Megakaryocytes, which fragment to form platelets. Platelets clot blood and recruit collagen-producing cells (fibroblasts) to the scene of an injury
  • These diverse cells develop from myeloid stem cells (blasts) inside the bone marrow. This process is mediated by different signals that steer the growth and division of the blasts, down different pathways (lineages)
  • The different blood cells can thus be considered “cousins” of each other. This is because they share a common ancestral stem cell, though they have diverged down separate lineages
  • The presence of any abnormalities in the blasts, or their signaling system, may disrupt their development and cause MDS. Different forms of myelodysplastic syndromes are classified, based on the cause or specific abnormalities produced
  • Refractory anemia is a deficiency in circulating red blood cells that resists treatment. It often results from defects, during red blood cell formation. It is mostly treatable, only through blood transfusions
  • Normally, blasts should comprise 5% or less of cell population inside the bone marrow. In RAEB, stem cells that have not differentiated accumulate to levels above 5%. There are 2 types of Refractory Anemia with Excess Blasts:
    • Type 1 RAEB: Characterized by 5-9% blasts in bone marrow and less than 5% blasts in blood
    • Type 2 RAEB: Characterized by 10-19% blasts in bone marrow, 5-19% blasts in blood, or white blood cells containing certain elongated structures, called Auer rods
  • Refractory Anemia with Excess Blasts is characterized by elevated numbers of myeloid stem cells inside the bone marrow; the Auer rods may also be present
  • The prognosis of Refractory Anemia with Excess Blasts depends on its severity; nevertheless, the prognosis of the condition is generally guarded

Who gets Refractory Anemia with Excess Blasts? (Age and Sex Distribution)

Individuals at risk for Refractory Anemia with Excess Blasts include:

  • Elderly individuals, aged 60 years and over
  • Men are more prone to the condition, than women

What are the Risk Factors for Refractory Anemia with Excess Blasts? (Predisposing Factors)

Following are factors that increase one’s susceptibility to Refractory Anemia with Excess Blasts:

  • Smoking
  • Exposure to radiation
  • Exposure to certain industrial chemicals
  • Chemotherapy

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Refractory Anemia with Excess Blasts? (Etiology)

  • Refractory Anemia with Excess Blasts is caused by genetic mutations. These may include missing regions of DNA, such as with 5q-syndrome, or other unknown defects
  • Regardless of the type of genetic abnormality, the problem is found in DNA regions that give instructions that are essential to proper blood cell maturation, inside the bone marrow
  • The genetic mutations can result from improper pairing of DNA during conception. Mutations can also occur after exposure to DNA-damaging agents, such as radiation and chemotherapeutic drugs. This is called therapy-related myelodysplastic syndrome (t-MDS); such conditions are more serious

What are the Signs and Symptoms of Refractory Anemia with Excess Blasts?

Indicators for Refractory Anemia with Excess Blasts include:

  • Pale appearance (pallor)
  • Fatigue
  • Difficulty adapting to altitude changes

How is Refractory Anemia with Excess Blasts Diagnosed?

Following are diagnostic techniques that may aid in the identification of Refractory Anemia with Excess Blasts:

  • Physical examination and evaluation of medical history
  • Blood smear tests to detect:
    • Anemia
    • Increased numbers of blast cells
    • Abnormally-shaped cells
    • Elongated structures called Auer rods, inside the white blood cells
    • Cellular fragments
  • Bone marrow biopsy to detect increased numbers of blast cells
  • Genetic studies of the relevant genes to detect abnormalities
  • Flow cytometric analysis on bone marrow

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Refractory Anemia with Excess Blasts?

The following complications may arise from Refractory Anemia with Excess Blasts:

  • Transformation of the condition to acute myeloid leukemia (AML); which is known to occur in 25% of Type 1 RAEB cases and 33% of Type 2 RAEB cases
  • Worsening of anemia

How is Refractory Anemia with Excess Blasts Treated?

Treatment measures for Refractory Anemia with Excess Blasts include:

  • The use of immunosuppressive drugs to prevent progression to leukemia, such as:
    • Antithymocyte globulin
    • Cyclosporine
  • Targeted molecular therapy drugs, such as:
    • Lenalidomide
    • Farnesyltransferase inhibitors
  • Bone marrow transplant may be performed in younger patients

How can Refractory Anemia with Excess Blasts be Prevented?

Refractory Anemia with Excess Blasts may be avoided by:

  • Limiting (exposure to) the following factors:
    • Radiation
    • Industrial chemicals
    • Chemotherapy
  • Quitting smoking

What is the Prognosis of Refractory Anemia with Excess Blasts? (Outcomes/Resolutions)

  • The severity of Refractory Anemia with Excess Blasts depends on the degree to which blast cell levels are elevated, and if Auer rods are present. These are also associated with the probability of the disease progressing to leukemia
    • If blast cell levels are 5-9% and Auer rods are absent (Type 1 RAEB), the prognosis is around 18 months survival
    • If blast cell levels are 10-19% or Auer rods are present (Type 2 RAEB), the prognosis is around 10 months survival
  • Proper care should be taken to treat and control complications from MDS. Often, the problems associated with infection, bleeding, and progression to leukemia, are the most dangerous aspects of the disease

Additional and Relevant Useful Information for Refractory Anemia with Excess Blasts:

Refractory Anemia with Excess Blasts is the most common form of myelodysplastic syndrome. Roughly, 40% of MDS cases are due to RAEB.

What are some Useful Resources for Additional Information?

American Cancer Society (ACS)
250 Williams Street NW, Atlanta, Georgia, 30303
Toll-Free: (800) 227-2345
TTY: (866) 228-4327
Website: http://www.cancer.org 

Aplastic Anemia & MDS International Foundation
100 Park Avenue, Suite 108, Rockville, Maryland 20850
Phone: (800) 747-2820
Fax: (301) 279-7205
Email: help@aamds.org
Website: http://www.aamds.org 

MDS Foundation
4573 South Broad Street, Suite 150, Yardville, NJ 08620
Phone: (800) MDS-0839 or (609) 298-1035 (if outside the US)
Fax: (609) 298-0590
Email: patientliason@mds-foundation.org
Website: http://www.mds-foundation.org 

Memorial Sloan Kettering Cancer Center
1275 York Avenue, New York, NY 10065
Phone: (212) 639-2000
Email: publicaffairs@mskcc.org
Website: http://www.mskcc.org 

Patient Registries at Slone: Myeloma & MDS
1010 Commonwealth Avenue, Boston, MA 02215
Email: registry@slone.bu.edu
Website: http://www.bu.edu/prs 

References and Information Sources used for the Article:

Cotran, R. S., Kumar, V., Collins, T., & Robbins, S. L. (1999). Robbins pathologic basis of disease (8th ed.). Philadelphia: Saunders.

Farhi, D. C. (2009). Pathology of bone marrow and blood cells (2nd ed.). Philadelphia: Wolters Kluwer Health/Lippincott William & Wilkins.

Hoffman, R. (2005). Hematology: Basic principles and practice (4th ed.). Philadelphia, Pa: Churchill Livingstone.

Hsi, E. D. (2012). Hematopathology (2nd ed.). Philadelphia, Pa: Elsevier/Saunders.

Pathology Student. (2011, December 27). Retrieved March 8, 2014, from http://www.pathologystudent.com/?p=4868

Helpful Peer-Reviewed Medical Articles:

DoveMed is currently working on a peer-reviewed database, to complement the information presented. Please do check back periodically.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 2, 2014
Last updated: March 24, 2017

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