Acute myeloblastic leukemia.

Myelodysplastic syndromes (MDS) are a group of clonal cell disorders characterized by maturation defects, resulting in ineffective hematopoiesis. They often transform to acute myeloblastic leukemia (AML), which is difficult to treat and carries a dismal prognosis. Azacitidine is a hypomethylating agent approved for the treatment of patients with MDS, including AML with 20% to 30% bone marrow blasts, according to World Health Organization classification. The three patient cases presented in this paper exemplify the spectrum of antitumor activity and toxicity of azactidine in patients where MDS transformed to AML.