Myelodysplastic Syndromes

The myelodysplastic syndromes (MDS) are clonal hematopoietic disorders that commonly cause macrocytic anemia in older patients. While the progeny of the mutant stem cells dominate the bone marrow, blood cell production rates are usually low because bone marrow cells do not mature normally and many of them undergo apoptosis in the bone marrow before reaching the peripheral blood.

Thus MDS is characterized by ineffective hematopoiesis. The characteristic feature in the bone marrow is dysplastic and/or megaloblastic maturation. Although the differentiation process is less perturbed than in acute leukemia (where the leukemic cells are incapable of maturing beyond the blast stage), subtle differentiation abnormalities defines MDS. Over time, the bone marrow cells of a substantial number of patients with MDS evolve to acute leukemia. Patients with MDS cannot be cured except by stem cell transplantation, and represent a considerable therapeutic challenge due to the limited effectiveness of most medical therapies.

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