The myelodysplastic syndromes are a diverse collection of hematological conditions united by ineffective production (or dysplasia) of myeloid blood cells and risk of transformation to acute myelogenous leukemia (AML). MDS has been found in humans, cats and dogs. Anemia requiring chronic blood transfusion is frequently present. Myelodysplastic syndromes are bone marrow stem cell disorders resulting in disorderly and ineffective hematopoiesis (blood production) manifested by irreversible quantitative and qualitative defects in hematopoietic (blood-forming) cells. In a majority of cases, the course of disease is chronic with gradually worsening cytopenias due to progressive bone marrow failure. Approximately one-third of patients with MDS progress to AML within months to a few years. Astronomer Carl Sagan was afflicted with this condition. Other notable people including writer Roald Dahl, jazz saxophonist Michael Brecker and actress Nina Foch died of this condition.