Hemosiderin

Hemosiderin or haemosiderin is an iron-storage complex that is composed of partially digested ferritin and lysosomes.

[6] In normal animals, hemosiderin deposits are small and commonly inapparent without special stains.

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.

Excessive systemic accumulations of hemosiderin may occur in macrophages in the liver, lungs, spleen, kidneys, lymph nodes, and bone marrow.

It is identified in cells by the Perls or Prussian blue reaction, in which ionic iron reacts with acid ferrocyanide to impart a blue color. Hemosiderin may deposit in diseases associated with iron overload.

Histopathology of a case of chronic pulmonary congestion, showing interstitium with hemosiderin deposition (black arrow), edema and collagenous thickening. The alveolus contains a siderophage (white arrow, characterized by coarse brown pigment, which is slightly refractile).
Hemosiderin image of a kidney viewed under a microscope. The brown areas represent hemosiderin