The exact cause of MDS is not known to date. Some evidence suggests that some people are predisposed to develop MDS at birth. This condition can be seen as a switch triggered by an external factor. If this external factor cannot be identified, the disease is referred to as “primary MDS”. Radiation therapy and chemotherapy for cancer are known triggers for the development of MDS. When patients take chemotherapy drugs or receive radiation therapy to treat potentially curable cancers (such as breast or testicular cancer, Hodgkin’s disease and non-Hodgkin’s lymphoma), they are at risk of developing MDS for up to 10 years after treatment. MDS that develops after chemotherapy or radiation therapy for cancer is called “secondary MDS” and is usually associated with multiple chromosomal abnormalities in the bone marrow cells. Long-term exposure to specific environmental or industrial chemicals, such as benzene, can also trigger MDS. Although the use of benzene is now highly regulated, it is unclear what other chemicals may predispose people to MDS, and certain occupations have been labeled as “susceptible” to MDS or AML. Certain occupations have been labeled as “susceptible” to MDS or AML, such as painters, coal miners, and embalmers. There are no known foods or agricultural products that can cause MDS. Although daily alcohol consumption may lower red blood cell and platelet counts, alcohol does not cause MDS, and there is not enough data to prove that smoking increases the risk of developing MDS. However, it is known that smokers have 1.6 times the risk of developing AML as non-smokers. Patients and their families are often concerned about whether MDS is contagious. There is no evidence that viruses can cause MDS; therefore, MDS is not contagious to loved ones. MDS is not hereditary. In fact, it is very rare for family members (including siblings) to be diagnosed with MDS at the same time.