Myelodysplasia is thought to result from an immune system abnormality in which cells called lymphocytes attack the marrow's blood-forming cells. The resulting deficiencies of platelets and red and white blood cells cause anemia, susceptibility to infections, and easy bruising and bleeding. Various therapies, such as blood transfusions for anemia and bleeding, antibiotics for infection, chemotherapy and bone marrow transplantation are used to treat myelodysplasia, but all have disadvantages and some carry serious risks.