Myelodysplastic Syndrome

Disease of bone marrow cells

There are several subtypes of myelodysplastic syndromes (MDS), but they are all disorders in which the cells in the bone marrow don't function normally and not enough normal blood cells are produced. MDS usually occurs in older people, typically starting after age 50. Myelodysplastic syndrome is rarely inherited. For many people, it develops without any known cause. In other people, MDS may develop after being exposed to chemotherapy or radiation therapy. Exposures to industrial chemicals such as benzene are also linked to the development of MDS.

Symptoms

The symptoms of myelodysplastic syndrome are related to the lack of normal blood cells.

• Lack of red blood cells causes anemia (leading to fatigue and shortness of breath)
• Lack of white blood cells leaves the body open to infection
• Lack of platelet cells makes it difficult for the blood to clot (leading to unusual bruising or bleeding)

Different people are affected in different ways by myelodysplastic syndrome, and its symptoms can range from mild to very severe. Some people may only have long-term (chronic) anemia.

Diagnosis

The symptoms a person is having, such as fatigue and shortness of breath, may suggest a diagnosis of myelodysplastic syndrome. A complete blood count and blood smear are done to look at the numbers and types of blood cells in a blood sample. In MDS, the numbers of red cells, white cells, and platelets may be lower than normal.

If the blood cell counts are abnormal, a bone marrow sample (biopsy) may be taken and examined under the microscope for abnormal immature white blood cells called leukemic blast cells. Not all individuals with myelodysplastic syndrome will have this type of cell in the bone marrow.

Special testing called cytogenetics will look at the genetic material (chromosomes) in the bone marrow cells. Certain types of abnormal chromosomes are present in myelodysplastic syndrome. For example, pieces of chromosome 5 or 7 may be missing, or there may be three copies of chromosome 8 instead of the normal two copies. Finding these abnormal chromosomes helps confirm the diagnosis and determine the course of treatment.

Classification

There are two main ways of classifying myelodysplastic syndrome. The FAB (French American British) system divides MDS into five subgroups. The World Health Organization (WHO) developed a different classification system with two main subgroups. These are:

• Chronic and nonprogressive anemia - blood cell count deficiencies without evidence of leukemic blast cells
• Progressive and symptomatic blood cell deficiencies - there are leukemic blast cells in the bone marrow

If the leukemic blast cells make up more than 20% of the bone marrow, the individual is considered to have acute myelogenous leukemia (blood cancer).

Treatment

Treatment depends on the type of myelodysplastic syndrome present, including if blast cells are present and what type of abnormal chromosome exists. Many treatment options are available. It is also important to consider what other medical problems an individual might have, such as diabetes or high blood pressure, along with the myelodysplastic syndrome when considering treatment.

Individuals who have long-term disease that is stable often are not treated, but have their symptoms monitored to see if the disease becomes worse. Sometimes years may pass before any changes occur.

For individuals with anemia, blood transfusions and/or drugs to stimulate blood cell development such as Epogen or Procrit (erythropoietin) may be given. Sometimes another drug called granulocyte colony stimulating factor (GCSF) is given along with the erythropoietin. Aranesp (darbepoetin alfa), a long-acting form of erythropoietin, may also be given.

Other medications that are used to treat myelodysplastic syndrome are Dacogen (decitabine) and Vidaza (azacitidine). Revlimid (lenalidomide) treats a specific type of MDS.

For severe myelodysplastic syndrome, most often treatment involves chemotherapy. Some individuals with very severe disease may receive a stem cell (bone marrow) transplant to replace the unhealthy bone marrow cells with healthy ones that can produce normal blood cells.

_Sources:

"General Information About Myelodysplastic Syndromes." Myelodysplastic Syndromes (PDQ®). 24 Mar 2006. National Cancer Institute. 6 Jan 2007.

"Myelodysplastic Syndrome." Disease Information. 03 Apr 2006. The Leukemia & Lymphoma Society. 27 Nov 2007.