Hemosiderin

Hemosiderin image of a kidney viewed under a microscope. The brown areas represent hemosiderin

Heme b. Iron is at center.

Hemosiderin or haemosiderin is an iron-storage complex. It is always found within cells (as opposed to circulating in blood) and appears to be a complex of ferritin, denatured ferritin and other material. The iron within deposits of hemosiderin is very poorly available to supply iron when needed.

Several disease processes result in deposition of larger amounts of hemosiderin in tissues; although these deposits often cause no symptoms, they can lead to organ damage.

Hemosiderin is most commonly found in macrophages and is especially abundant in situations following hemorrhage, suggesting that its formation may be related to phagocytosis of red blood cells and hemoglobin. Hemosiderin can accumulate in different organs in various diseases.

Iron is required by many of the chemical reactions (i.e. oxidation-reduction reactions) in the body but is toxic when not properly contained. Thus, many methods of iron storage have developed.

Pathophysiology

Hemosiderin often forms after bleeding (hemorrhage). When blood leaves a ruptured blood vessel, the red blood cell dies, and the hemoglobin of the cell is released into the extracellular space. White blood cells called macrophages engulf (phagocytose) the hemoglobin to degrade it, producing hemosiderin and porphyrin.

Porphyrin is not a breakdown product of red blood cells or hemoglobin.

Diseases associated with hemosiderin deposition

Main article: Hemosiderosis

Hemosiderin may deposit in diseases associated with iron overload. These diseases are typically diseases in which chronic blood loss requires frequent blood transfusions, such as sickle cell anemia and thalassemia.