Myelodysplastic Syndrome

Overview
  • Myelodysplastic Syndromes (MDS) are a grouping of disorders characterized by a clonal proliferation of defective neoplastic hematopoietic stem cells that typically results in ineffective blood cell production, leading to anemia and often pancytopenia. Patients with MDS have a higher risk of developing AML.
Etiology and Pathogenesis
  • The pathogenesis of MDS is poorly understood but is thought to involve the proliferation of a neoplastic clone of hematopoietic stem cells that are ultimately defective in producing viable peripheral blood cells. Consequently, myelodysplasia is characterized by ineffective erythropoiesis and cytopenias which may include normocytic anemia, thrombocytopenia, and neutropenia.
  • MDS typically affects an elderly population and in most cases the etiology is unknown and thus considered idiopathic; however, in some patients a clear historical insult to the bone marrow can be identified and can include radiation, toxins such as benzene, or certain chemotherapeutics.
Morphology
  • In most patients the bone marrow is markedly hypercellular, signifying the replacement of the bone marrow with the neoplastic clone of hematopoietic stem cells. However, blood line maturation is disorganized, dysplastic and ultimately ineffective in producing viable peripheral cells
  • Within the bone marrow ringed sideroblasts can be seen
Clinical Consequences
  • The clinical consequences of MDS are predictable given the degree of pancytopenia and which blood lines are most prominently affected. Patients with anemia will develop the classic symptomology of fatigue, light-headedness, and dyspnea on exertion (See anemia page). Those with thrombocytopenia will develop ecchymoses and petechiae while those with neutropenia will display susceptibility to infections.
  • The prognosis for MDS is variable but generally poor. Most patients die of cytopenic complications; however, in those who survive, the most feared complication is transformation of the neoplastic cells into outright Acute Myeloid Leukemia.