The exact cause of myelodysplastic syndromes (MDS) has not been identified. However, researchers have gained a greater understanding of how specific changes in DNA (deoxyribonucleic acid) can cause bone marrow stem cells to develop into MDS.

DNA is the genetic material that houses instructions for all of the body’s chemical processes. Some forms of cancer are caused by DNA mutations that “turn on” oncogenes (genes that speed up cell division) or “turn off” tumor suppressor genes (genes that slow down cell division or cause cells to die at the right time). In people with MDS, mutations may occur from exposure to radiation or cancer-causing chemicals, but many times the mutations occur for no apparent reason.

Another form of DNA abnormality that can cause MDS to develop is a translocation. A translocation is the transfer of DNA from one chromosome to another. This abnormality can turn on oncogenes, which causes rapid cell division, or turn off tumor suppressor genes. Additional abnormalities that may be found in patients with MDS include:

• Additions. Part of a chromosome is duplicated and too many copies of it are found within the cell.
  
  
• Deletions. The loss of part of a chromosome.

In addition, researchers have identified a number of factors that may make a person more likely to develop MDS. These risk factors include:

• Age. Being over the age of 60 is considered a risk factor for MDS because most patients with MDS are elderly.
  
  
• Chemotherapy. Patients treated for other cancers with certain chemotherapy drugs are at an increased risk of developing MDS. The risk is even greater for those treated with a combination of chemotherapy and radiation therapy. MDS that occurs after treatment for an earlier cancer are known as secondary MDS. They most often develop after treatment for Hodgkin’s lymphoma, non-Hodgkin’s lymphoma and childhood acute lymphocytic leukemia (ALL). Secondary MDS sometimes occur following treatment for other cancers, including breast cancer, lung cancer, testicular cancer and ovarian cancer.
  
  
• Smoking. Tobacco smoke contains cancer-causing substances (carcinogens) that are absorbed by the lungs and spread through the bloodstream to numerous parts of the body. As a result, smoking increases the risk of developing a number of cancers, including MDS.
  
  
• Exposure to very high levels of radiation. Patients who have received radiation therapy as treatment for other forms of cancer have an increased risk of developing MDS later in life. In addition, people exposed to radiation from atomic blasts (such as those in Japan during World War II) and nuclear accidents have an increased risk of developing MDS.
  
  
• Benzene. Benzene is a colorless, flammable liquid used primarily as a solvent and a gasoline additive. It is also a component of cigarette smoke. Long-term exposure to the chemical can increase a person’s risk of developing MDS. Long-term exposure to certain other chemicals used in the petroleum and rubber industries can also increase the risk.
  
  
• Fanconi’s anemia. This condition affects the bone marrow, resulting in decreased production of blood cells. People with this condition are more likely to develop MDS.
  
  
• Family history. MDS has been found to occur frequently in some families.
  
  
• Gender. MDS occurs slightly more often in men.

Although MDS is associated with these risk factors, many patients with the diseases have no known risk factors.