What is Hemosiderin?

You have heard the term hemosiderin, and you have probably ordered a urine hemosiderin test in a patient with suspected hemolytic anemia and hemoglobinuria. But what is it exactly? And how does it relate to iron and ferritin?

  • There are two storage forms of iron are known in animals:
    • Ferritin
    • Hemosiderin
  • Both are present in virtually all cells/tissues but occur principally in liver, spleen, and bone marrow.
  • Both contain the ferric form of iron (Fe3+).
  • Ferritin degradation in lysosomes gives rise to hemosiderin.
  • Hemosiderin consists of aggregates of insoluble, denatured ferritin molecules from which much of the protein shell has been removed by proteolytic digestion.12
  • Tissue staining with Perls Prussian blue is able to detect hemosiderin (shows a punctate pattern of staining), but not ferritin.3
  • While the normal pathway for iron storage flows from ferritin to hemosiderin:
    • Hemosiderin can form through ferritin-independent pathways (when the rate of uptake of iron exceeds the tissue’s capacity to make ferritin protein).
    • Hemosiderin-associated iron can recycle back to ferritin (albeit inefficiently).4
Iron stateFe3+Fe3+
Iron content16-23 %24-45 %
Protein shellYesNo
Water solubleYesNo
Located in lysosomes+/-Yes
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