To review evidence supporting the involvement of interleukin-6 in the pathophysiology of anemia of chronic disease, to discuss the possible molecular mechanisms driving this condition in patients with end-stage renal disease and rheumatoid arthritis, and to review clinical manifestations in these patients.
A literature search was performed using MEDLINE and the reference lists of relevant review articles. The following key words were used in the MEDLINE search: interleukin-6, "anemia of chronic disease" OR "anemia of inflammation," "pathophysiology," "end-stage renal disease," and "rheumatoid arthritis." The search was limited to English-language articles.
Interleukin-6 is a multifunctional cytokine that regulates the hepatic acute-phase response, the immune response, inflammation, and hematopoiesis. Interleukin-6 appears to be the central mediator of anemia of chronic disease in a range of inflammatory diseases, including end-stage renal disease and rheumatoid arthritis, through increased generation of hepcidin and the resultant alterations in iron metabolism. Clinically, patients with anemia of chronic disease are more likely to experience increased disease severity and duration than patients who have chronic disease without anemia.
The integral role of interleukin-6 in the pathogenesis of anemia of chronic disease suggests that it could be an important therapeutic target. Currently available treatments target interleukin-1, and tumor necrosis factor-alpha and its receptors, and have been only partially successful. Given the complexity of the cytokine pathways that are involved in the pathogenesis of inflammatory disease, further studies are required to test other molecular targets.