Anemia of chronic disease.

Anemia of chronic disease (ACD) or inflammation may be secondary to infections, autoimmune disorders, chronic renal failure, or malignancies. It is characterized by an immune activation with an increase in inflammatory cytokines and resultant increase in hepcidin levels. In addition, inappropriate erythropoietin levels or hyporesponsiveness to erythropoietin and reduced red blood cell survival contribute to the anemia. Hepcidin being the central regulator of iron metabolism plays a key role in the pathophysiology of ACD. Hepcidin binds to the iron export protein, ferroportin, present on macrophages, hepatocytes, and enterocytes, causing degradation of the latter. This leads to iron trapping within the macrophages and hepatocytes, resulting in functional iron deficiency. Production of hepcidin is in turn regulated by iron stores, inflammation, and erythropoiesis via the BMP-SMAD and JAK-STAT signaling pathways. Treatment of anemia should primarily be directed at the underlying disease, and conventional therapy such as red blood cell transfusions, iron, erythropoietin, and novel agents targeting the hepcidin-ferroportin axis and signaling pathways (BMP-SMAD, JAK-STAT) involved in hepcidin production also may be considered.