Myelodysplastic syndrome (MDS) has a few known risk factors:

• People who have already had chemotherapy or radiation treatment for cancer have an increased risk of therapy-related MDS. This is because chemotherapy drugs and radiation therapy can damage the stem cells in the bone marrow. When chemotherapy drugs are combined with radiation therapy, the risk of developing MDS and leukemia is higher.
• People who have been exposed to high levels of benzene or radiation over long periods of time are also at a greater risk of developing MDS.

The majority of people who develop MDS have no identifiable risk factors. Scientists do know that many cases of MDS are associated with specific changes in the DNA of bone marrow cells. It is often not clear what causes those changes. There are many types of MDS, so it is likely that there are many different causes of MDS.