Iron status in chronic inflammatory disease: therapeutic implications

Anemia of inflammation (AI) is a very frequent clinical condition affecting globally more than a billion people with chronic inflammatory disorders, such as chronic kidney disease, heart failure, and inflammatory bowel disease. It is usually associated with iron deficiency (ID), which imposes a severe additional burden on the recovery from the primary disease. The pathophysiology of iron dysregulation that may ultimately lead to absolute iron deficiency anemia (IDA) during inflammation is multifactorial and includes reduced iron absorption in the bowel, iron retention in macrophages of the reticuloendothelial system, reduction in circulatory half‑life of erythrocytes, inadequate production and activity of erythropoietin, and impaired proliferation and differentiation of erythroid progenitor cells. These result in hypoferremia and iron-restricted erythropoiesis. AI is mostly mild to moderate, normochromic and normocytic with normal or even increased ferritin levels. The current treatment options for AI include iron replacement therapy, treatment with erythropoiesis‑stimulating agents, and red blood cell transfusion. ID management is based on oral or intravenous iron preparations. Given the pathophysiology, treatment with oral iron, although widely used, presents several limitations that impact its effectiveness in patients with chronic inflammatory conditions. Instead, intravenous iron preparations are a valuable option for patients with chronic inflammatory diseases, as they overcome reduced bowel absorption. Novel therapeutic approaches include downregulation of hepcidin synthesis and function, and stabilization of the hypoxia‑inducible factor via inhibition of prolyl hydroxylase domain. Several studies in vitro and in vivo are ongoing; however, the results in humans are still elusive.