Myelodysplastic syndromes (MDS) are a group of diseases that affect the body’s blood-making system. Although they were considered to be a different type of disease for many years, most hematologists (physicians who specialize in diseases of the blood and blood-forming tissues) now consider MDS to be a form of cancer. In addition, MDS progresses to acute myeloid leukemia (a cancer of bone marrow cells) in approximately 30 percent of patients. As a result, some physicians consider it an early form of the disease.

Bone marrow is the soft, inner component of bones, where white blood cells, red blood cells and platelets are formed. In patients with MDS, the bone marrow fails to produce enough normal blood cells. Over time, the shortage in normal blood cells can result in anemia, bleeding disorders and a decreased ability to fight off infection.

The exact cause of MDS has not been identified. Researchers, however, have gained a greater understanding of how specific changes in DNA (deoxyribonucleic acid) can cause cells to develop into MDS. A number of risk factors have also been identified, including age, smoking and environmental exposures such as radiation or certain chemicals. In addition, patients treated with chemotherapy or radiation for other cancers have a higher risk of developing MDS.

Symptoms of MDS vary depending on where it has spread in the body. General signs and symptoms include weight loss, fever, loss of appetite and weakness.

MDS may be first diagnosed in routine blood tests. However, additional tests may be necessary, including bone marrow tests and a complete blood count. The treatment and prognosis (outlook for recovery) for MDS depends on the subtype of the disease, as well as certain additional factors including the patient’s age. Treatment may include bone marrow/stem cell transplantation or a form of supportive therapy (e.g., blood transfusion, antibiotics), used to treat the symptoms or complications of the disease.

The exact number of MDS cases in the Unites States is unknown because there is no registry tracking system for the disease. The American Cancer Society (ACS) estimates that there are between 10,000 and 15,000 new cases each year. The disease is more common in the elderly, with about 80 to 90 percent of cases occurring in patients over the age of 60. MDS rarely occurs in young adults.