Myelodysplastic Syndrome (MDS) is a type of cancer that occurs when the blood-forming cells in the bone marrow are damaged. This results in low numbers of red or white blood cells or platelets.
In a minority of cases (about one-third), MDS can progress to a rapidly growing cancer of bone marrow cells, called acute myeloid leukemia. Because of this, the disease was long referred to as pre-leukemia or smoldering leukemia. But most MDS patients do not get leukemia, so these terms are now considered inaccurate and MDS is classified as a unique form of cancer.
There are seven categories of MDS, as classified by the World Health Organization (WHO):
Some of these have low numbers of one type of blood cell, but normal numbers of the other two types. Others have low numbers of two blood cell types. Some types progress to acute myeloid leukemia and some do not. Some of these affect lifespan while others have very little impact. The cancer is called primary MDS when no cause can be identified and secondary MDS when the cause of the disease is known. This identification is important because secondary MDS, which is most often caused by prior cancer treatment, is much less likely to respond to treatment.
The biggest risk factor for developing MDS is having had prior chemotherapy treatment, although the overall risk of developing MDS after chemotherapy is small. Combining chemotherapy with radiation increases the risk further.
The risk of MDS increases with age: the cancer rarely occurs before age 40, and is most prevalent in people over 60. MDS is more common in men than women. Smoking is a known risk factor. Environmental risk factors, such as radiation and exposure to benzene and some chemicals used in the petroleum and rubber industries have been linked to MDS. People with certain inherited syndromes, including Fanconi anemia, Shwachman-Diamond syndrome, familial platelet disorder, and severe congenital neutropenia are more likely to develop MDS.
Symptoms of MDS depend on which type of blood cell is affected. A shortage of red blood cells (anemia) can lead to fatigue and shortness of breath. A lack of normal white blood cells (leukopenia) can lead to severe infections, including pneumonia. Being low on blood platelets can result in severe bruising and bleeding from even the slightest bumps or cuts. Other symptoms can include weight loss, fever, and loss of appetite. These problems are more often caused by something other than cancer but should be checked out.
There are currently no screening tests to detect MDS in its early stages. People who have had prior chemotherapy treatment for other cancers should be closely monitored.
Chemotherapy is the standard treatment for MDS. Newer treatments, including stem cell transplants, the use of growth factors to stimulate blood cell production, blood transfusions, and targeted therapy are now being used more widely as their efficacy progresses.