Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) refer to a group of disorders in which the bone marrow stem cells — the primitive cells that give rise to all the different types of blood cells — are defective, causing an inadequate production of blood cells. Patients with MDS usually suffer from low counts of red blood cells, white blood cells or platelets, or a combination.

MDS was previously mischaracterized as "pre-leukemia" or "smoldering" leukemia because of its tendency to transform into acute myeloid leukemia.

The cause of MDS remains unknown. It occasionally develops after treatment with drugs or radiation for another medical condition, or after exposure to chemicals such as benzene or toluene. MDS occurs in older patients, often age 65 or older, which suggests that age may be the strongest risk factor for developing MDS.

Many kinds of treatments are available for MDS, including new medications and stem cell transplantation.

In myelodysplastic syndromes, the bone marrow is heavily infiltrated with MDS cells, which do a poor job of producing mature blood cells. Signs and symptoms include:

  • Low red blood cells counts, causing fatigue and shortness of breath
  • Abnormal white blood cells called neutrophils, which kill germs poorly, resulting in infection with bacteria, fungi or atypical mycobacteria (relatives of tuberculosis)
  • Low platelet counts, causing bleeding

The typical MDS patient is 60 to 80 years old with mild to modest anemia — low levels of red blood cells — in which iron, vitamin and endocrine gland deficiencies have been ruled out as a cause. The anemia usually progresses and reaches a point where the patient needs red blood cell transfusions.

MDS is generally diagnosed when a patient is evaluated for low blood counts, although in some MDS patients, the white blood count, platelet count, or both may be elevated. The hallmark feature of MDS is a bone marrow aspirate and biopsy that reveals heavy infiltration with abnormal-looking bone marrow cells. (Myelodysplasia means "funny-looking bone marrow.") A chromosome analysis, called cytogenetics, is performed on the bone marrow sample.

In patients with MDS, immature cells called blasts make up less than 20 percent of the cells in the bone marrow. If blast cells make up more than 20 percent, the patient is diagnosed with acute myeloid leukemia.

Subtypes of MDS

MDS has been classified into several different subtypes, which are largely determined by the percentage of blast cells in the bone marrow:

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The only known cure for MDS is allogeneic blood and marrow transplantation (BMT). Due to the older age of MDS patients and the intensity of allogeneic BMT, however, this treatment often isn't appropriate for MDS patients.

Allogeneic BMT achieves a cure through a combination of high-dose chemotherapy just before the transplant and an attack of the donor's immune cells against the patient's MDS cells, known as graft-versus-leukemia effect.

If allogeneic BMT is not appropriate for a patient, treatment is geared toward relieving symptoms, reducing the need for transfusions, deferring conversion to acute myeloid leukemia, and improving the quality and length of life. It does not aim to achieve a cure.

The major treatment strategies are:

  • Supportive care
  • Epigenetic therapy
  • Biologic therapy

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Reviewed by health care specialists at UCSF Medical Center.

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