Lisa Chodirker, MD, FRCPC, Clinical Fellow, Division of Hematology/Oncology, Odette Cancer Centre*, Sunnybrook Health Sciences Centre, Toronto, ON.
Rena Buckstein, MD, FRCPC, Co-director of MDS research programs, Division of Hematology/Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON.

Myelodysplastic syndromes (MDS) are among the most common hematological malignancies in Western countries, with a median age at diagnosis of 74. They are a stem cell disorder characterized by cellular dysplasia, cytopenias, and an increased risk of transformation to acute myeloid leukemia. Disease trajectory is commonly determined by the international and world prognostic scoring systems (International Prognostic Scoring System and the World Health Organization [WHO] classification–based prognostic scoring system) and the WHO classification. Some patients have an indolent disease course, while others experience a rapid deterioration and short overall survival. For many years, the mainstay of therapy was supportive care with blood transfusions and hematopoietic growth factors. Fortunately, novel effective agents including lenalidomide, hypomethylating agents, and oral iron chelators have emerged over the past 5–10 years that improve transfusion dependence and may alter the natural history of the disease. These new therapeutic options offer new hope for individuals with MDS and bolster the role for the investigation of unexplained cytopenias in the older patient.
Key words: myelodysplastic syndrome, erythropoietin, anemia, red blood cell transfusions, stem cell disorder.

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.