Richard A. Wells, MD, DPhil, FRCP(C), Assistant Professor of Medicine, University of Toronto; Staff Physician, Leukaemia Group, Princess Margaret Hospital; Scientist, Ontario Cancer Institute, Toronto, ON.

In myelodysplastic syndrome (MDS), genetic mutations in bone marrow stem cells result in production of defective blood cells. These defective cells fail to meet the intrinsic "quality control" standards of the bone marrow and are not released into the circulation, leading to anemia, leukopenia or thrombocytopenia. In some, but not all, patients with MDS, there also is a greatly increased risk of development of acute myelogenous leukemia. Until very recently, therapeutic options in MDS were extremely limited. This article reviews recent advances in risk-based classification of MDS, and describes new therapies that promise to revolutionize our approach to patients with this disorder.
Key words: myelodysplastic syndrome, bone marrow, anemia, acute myelogenous leukemia.