Histopathology of a case of chronic pulmonary congestion, showing interstitium with<unk>  deposition (black arrow), edema and collagenous thickening. The alveolus contains a siderophage (white arrow, characterized by coarse brown pigment, which is slightly refractile).<unk>  image of a kidney viewed under a microscope. The brown areas represent<unk> <unk>  or<unk>  is an iron-storage complex that is composed of partially digested ferritin and lysosomes. The breakdown of heme gives rise to biliverdin and iron. The body then traps the released iron and stores it as<unk>  in tissues.<unk>  is also generated from the abnormal metabolic pathway of ferritin. It is only 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<unk>  is very poorly available to supply iron when needed.<unk>  can be identified histologically with Perls' Prussian blue stain; iron in<unk>  turns blue to black when exposed to potassium ferrocyanide. In normal animals,<unk>  deposits are small and commonly inapparent without special stains. Excessive accumulation of<unk>  is usually detected within cells of the mononuclear phagocyte system (MPS) or occasionally within epithelial cells of liver and kidney. Several disease processes result in deposition of larger amounts of<unk>  in tissues; although these deposits often cause no symptoms, they can lead to organ damage.<unk>  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.<unk>  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. __TOC__
Hemosiderin
Hematoporphyrin
Respiratory pigment
Iron metallic discoloration
Iron lung
Melanin
Fomite
Hemosiderosis