Advancements in anemias related to chronic conditions.

Anemia of chronic disease (ACD), the most frequent anemia among hospitalized patients, occurs in chronic inflammatory disorders, such as chronic infections, cancer and autoimmune diseases. Different causes contribute to ACD including diversion of iron traffic, diminished erythropoiesis, blunted response to erythropoietin, erythrophagocytosis, hematologic malignancies and solid tumors. A particular case of ACD is represented by anemia of chronic kidney disease (CKD). ACD is characterized by hyposideremia and altered iron transport. Cytokines are implicated in the ACD by reducing erythropoiesis and increasing iron sequestration in the reticuloendothelial system. The regulation of iron absorption across the epithelium of the proximal small intestine is essential for maintaining body iron concentrations within a physiologically defined range. Hepcidin controls cellular iron efflux by binding to the iron export protein ferroportin, causing ferroportin to be phosphorylated and degraded in lysosomes. Finally, hepcidin inhibits iron release from the reticulo-endothelial system. Increased expression of hepcidin leads to decreased iron absorption and iron deficient anemia. Hepcidin, therefore, is a negative regulator of iron transport in plasma. Causes of anemia in patients with CKD are multifactorial, but the most well-known cause is inadequate erythropoietin production. In these patients, anemia increases the risk of either cardiovascular disease or renal failure.