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Refractory Anemia with Ringed Sideroblasts (RARS)

Last updated Jan. 10, 2019

Approved by: Krish Tangella MD, MBA, FCAP

Refractory Anemia with Ringed Sideroblasts (RARS) 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.


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

  • RARS (Refractory Anemia with Ringed Sideroblasts)
  • Sideroblastic Anemia Associated with MDS

What is Refractory Anemia with Ringed Sideroblasts? (Definition/Background Information)

  • Refractory Anemia with Ringed Sideroblasts (RARS) 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
  • Refractory Anemia with Ringed Sideroblasts is characterized by refractory anemia with the presence of 15% or more, of immature red blood cells (erythroblasts) containing iron granules in a ring-shaped pattern. These are called ringed sideroblasts
  • The prognosis of RARS depends upon the severity of anemia and its response to treatment, which is usually with medication

Who gets Refractory Anemia with Ringed Sideroblasts? (Age and Sex Distribution)

Individuals at risk for Refractory Anemia with Ringed Sideroblasts 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 Ringed Sideroblasts? (Predisposing Factors)

The following factors may increase one’s susceptibility to Refractory Anemia with Ringed Sideroblasts:

  • 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 Ringed Sideroblasts? (Etiology)

  • Refractory Anemia with Ringed Sideroblasts 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 Ringed Sideroblasts?

Indicators for Refractory Anemia with Ringed Sideroblasts include:

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

How is Refractory Anemia with Ringed Sideroblasts Diagnosed?

Following are diagnostic techniques that may aid in identification of Refractory Anemia with Ringed Sideroblasts:

  • Physical examination and evaluation of medical history
  • Blood smear tests to detect:
    • Anemia
    • Abnormally-shaped cells
    • Ringed sideroblasts
    • Cellular fragments
  • Genetic studies of the relevant genes to detect abnormalities
  • Bone marrow biopsy
  • Flow cytometry 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 Ringed Sideroblasts?

The following complications may arise from Refractory Anemia with Ringed Sideroblasts:

  • Transformation of the condition to acute myeloid leukemia (AML), which may occur in less than 5% of cases
  • Worsening of anemia

How is Refractory Anemia with Ringed Sideroblasts Treated?

Treatment measures for Refractory Anemia with Ringed Sideroblasts 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 Ringed Sideroblasts be Prevented?

Refractory Anemia with Ringed Sideroblasts may be avoided by:

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

What is the Prognosis of Refractory Anemia with Ringed Sideroblasts? (Outcomes/Resolutions)

  • Refractory Anemia with Ringed Sideroblasts is considered a low-risk form of myelodysplastic syndrome (MDS). Generally, the prognosis depends on the severity of anemia and its response to treatment
  • 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 Ringed Sideroblasts:

Refractory Anemia with Ringed Sideroblasts should be differentiated from acquired sideroblastic anemia, which is not considered a type of MDS.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 2, 2014
Last updated: Jan. 10, 2019