EPO and myelodysplastic syndrome: Efforts to understand the pathophysiology of the so-called anemia of aging have specifically targeted different physiological age-related changes including erythropoietin (EPO) resistance and reduced proliferative capacity of bone marrow stem cells, stem cell aging, impaired renal function, myelodysplasia (MDS), and chronic inflammation with higher circulating levels of proinflammatory cytokines [8, 23, 24].