Myelodysplasia is not a single disease, but rather a group of disorders characterized by an inability to produce enough healthy mature blood cells. These disorders are also commonly called myelodysplastic syndromes, or MDS. In addition to causing problems such as anemia, the presence of myelodysplasia is sometimes considered a premalignant condition because a significant number of patients with it develop leukemia. Therefore, early diagnosis and treatment of myelodysplasia may prevent such an outcome.
  • City of Hope physicians and researchers continue to lead the way in improving diagnosis, treatments and outcomes in patients with myelodysplasia. City of Hope’s strategies address myelodysplasia using sophisticated genetic markers that aid in both diagnosis and treatment, advanced chemotherapy protocols using experimental drugs, and our nationally-recognized stem cell transplantation program, which specializes in “mini” hematopoietic cell transplants, allowing for transplantation in older myelodysplasia patients.
  • Our patients are cared for by a multidisciplinary team of professionals, including hematologists and oncologists, radiation oncologists, nurses, supportive care specialists, dieticians, therapists, social workers, psychiatrists, psychologists and pharmacists. Each member of the team focuses on individual treatment plans designed to extend life, as well as supportive care to improve the quality of life for patients and their families during the treatment period.
  • City of Hope’s Clinical and Translational Research Program has had continuous funding for the Hematopoietic Cell Transplantation (HCT)  Program by the National Cancer Institute since 1981. The MDS Foundation recognized City of Hope as a Center of Excellence for MDS in 1998 in recognition of the program’s basic and clinical research – one of only 34 hospitals worldwide to receive this designation.

About Myelodysplasia

Myelodysplasia refers to a set of syndromes (also called myelodysplastic syndromes, or MDS) in which the normal process of making mature blood cells (red blood cells, white blood cells, and platelets) – known as hematopoiesis – is impaired. Hematopoiesis begins with a hematopoietic stem cell (HSC) present in the bone marrow. The HSC is capable of differentiating into two more specialized stem cells: lymphoid stem cells and myeloid stem cells. Lymphoid stem cells differentiate into a type of white blood cell called a lymphocyte, while myeloid stem cells can differentiate into red blood cells, platelets, and a group of white blood cells called granulocytes and monocytes.


In myelodysplasia, the stem cells do not differentiate completely; they remain as immature “blast cells” instead of maturing into normal red blood cells, white blood cells and platelets. This results in a disproportionately low number of healthy mature blood cells, a condition known as cytopenia. When there is a shortage of red blood cells, this is called anemia. The corresponding deficiencies in the other cell types are called leukocytopenia (white blood cells) and thrombocytopenia (platelets). Each of these deficiencies is associated with a host of health problems such as bleeding (caused by low platelet counts) and infection (due to low white blood cell counts).

Besides the effects caused by a deficiency of normal blood cells, myelodysplasia often produces increased numbers of immature blast cells in the bone marrow. The accumulation of excess blast cells may result in some of the blasts becoming abnormal (their morphology, or form, is defective). This process is known as malignant transformation, and leads to leukemia. Hence, myelodysplasia is often considered to be a premalignant, or preleukemic condition, necessitating careful monitoring and intervention.

Types of Myelodysplasia

There are many different types of myelodysplastic syndromes, or MDS. These include:

  • Refractory anemia (RA)
    RA means a shortage of red blood cells that does not respond to conventional anemia treatment. In RA, only a low red cell count is apparent, and both white blood cell and platelet counts are normal. The clinical course of this disease is prolonged, and very rarely transforms into leukemia.
  • Refractory anemia with ringed sideroblasts (RARS)
    RARS is identical to RA, except for the distinction that 15 percent of the red blood cells are abnormal cells called ringed sideroblasts. A sideroblast is a red blood cell that contains iron deposits. As with RA, RARS has a protracted clinical course and rarely progresses to leukemia.
  • Refractory anemia with excess blasts (RAEB)
    In RAEB, myeloblasts account for 5 to 19 percent of the cells in the bone marrow, but the number of blasts in the peripheral blood is normal. There may be changes to the white blood cells and platelets. RAEB may progress to acute myeloid leukemia (AML); the higher the number of blasts, the shorter the clinical course of the disease and the higher the likelihood of transformation to AML.
  • Refractory anemia with excess blasts in transformation (RAEB-t)
    In RAEB-t, in addition to anemia (low red cell count), there is also a shortage of white blood cells and platelets. Here, these shortages are caused by the over-proliferation of blast cells. Some experts don’t even think RAEB-t should exist as a category, and consider it to actually be a form of AML.
  • Refractory cytopenia with multilineage dysplasia (RCMD)
    Here, there is a cytopenia (shortage of cells) of at least two members of the myeloid cell line (which comprises red blood cells, granulocyte-type white blood cells, and platelets) – hence the term “multilineage” – and they are dysplastic, or abnormal. Only a small percentage of RCMD cases progress to AML.
  • Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality
    In this MDS, also called “5q-,”patients are anemic, and there is what is known as a deletion abnormality on the “long arm” of chromosome 5 (the short end of a chromosome is called “p” and the long end, “q”). This subtype is associated with a long survival.
  • Unclassifiable myelodysplastic syndrome (MDS-U)
    WITH MDS-U, there is a shortage of at least one type of blood cell, and the number of blasts in both bone marrow and blood is normal. However, it cannot fit into any of the other classifications set forth above for MDS.
  • De novo myelodysplastic syndrome
    The term “de novo” just means “from new” in Latin, meaning the disease just seems to show up out of the blue with no known cause.
  • Secondary myelodysplastic syndrome
    This type of MDS is secondary to (meaning that it occurs as a consequence of) certain environmental factors such as exposure to the following:
    • Tobacco smoke
    • Ionizing radiation
    • Organic chemicals (e.g., benzene, toluene, xylene and chloramphenicol)
    • Heavy metals
    • Herbicides
    • Pesticides
    • Fertilizers
    • Stone and cereal dusts
    • Exhaust gases
    • Nitro-organic explosives
    • Petroleum and diesel derivatives
    • Alkylating agents (often used in cancer chemotherapy)
    • Marrow-damaging agents used in cancer chemotherapy
  • Previously treated myelodysplastic syndrome
    Previously treated MDS are de novo or secondary cases of MDS that have progressed despite previous treatment and, in many cases, are receiving additional treatment.
Myelodysplastic Risk Factors
Although many cases of myelodysplastic syndromes, or MDS, have no known cause, the following are commonly-accepted risk factors:
  • Age over 60 years (although pediatric cases do occur, especially after previous chemotherapy)
  • Being male and white
  • Past treatment with chemotherapy or radiation therapy
  • Exposure to certain chemicals, including tobacco smoke, pesticides, heavy metals such as mercury or lead, and solvents such as benzene. A more complete list of these environmental agents can be viewed above.
Myelodysplastic Symptoms
Myelodysplastic syndromes often do not cause early symptoms and are sometimes found during a routine blood test. Although the symptoms below may be indicative of myelodysplasia, other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
  • Shortness of breath
  • Weakness or feeling tired
  • Pallor (pale skin)
  • Easy bruising or bleeding
  • Petechiae (flat, pinpoint spots under the skin caused by bleeding)
  • Fever or frequent infections
  • Splenomegaly (enlargement of the spleen)