Myelodysplastic syndromes.

The myelodysplastic syndromes are a heterogeneous group of hematopoietic stem cell disorders characterized by dysplastic and ineffective hematopoiesis and a varying risk of transformation to acute leukemia. Although the natural history of these syndromes is variable, several factors appear to be of prognostic importance, including the French-American-British classification, the karyotype, in vitro colony formation, and others. The pathogenesis of the myelodysplastic syndrome is not known, but recent evidence suggests that alterations of cellular oncogenes may be a causative factor. There is no standard therapy for myelodysplasia, and thus novel approaches to patient management are warranted.