Myelodysplastic syndrome with excess blasts

Myelodysplastic syndrome with excess blasts (MDS-EB) represents the most clinically aggressive end of the continuum of the myelodysplastic syndromes (MDS). All MDS are characterized by clonal, ineffective hematopoiesis with maturation defects and increased apoptosis resulting in peripheral blood cytopenias, abnormal myeloid maturation (dysplasia) and variable risk of progression to bone marrow failure and/or acute myeloid leukemia. Progressive degrees of restricted myeloid maturation represented by abnormally increased numbers of morphologically-defined blasts in the blood and/or bone marrow is the key feature separating MDS-EB from the other myelodysplastic syndromes and is strongly associated with increased risk of disease progression and decreased survival. Metaphase chromosome analysis of bone marrow myeloid cells is the cornerstone of documenting clonal hematopoiesis to establish the diagnosis of MDS and for risk stratification of patients with confirmed MDS. Molecular analyses are becoming increasingly utilized for diagnosis and prognosis.