A transforming event in a hematopoietic stem cell causes genetic mutations resulting in clonal (neoplastic) hematopoietic disorders. Depending on the mutation, the cells can: a) mature abnormally and die prematurely, resulting in cytopenias and myelodysplasia or the myelodysplastic syndromes; b) Proliferate, crowding out normal hematopoiesis, resulting in acute leukemia; or c) Fail to die, accumulating to high numbers in blood, resulting in chronic leukemia. These are not always mutually exclusive events and, due to genomic instability, cells in chronic leukemia and myelodysplastic syndromes can mutate further and evolve into an acute leukemia.
