Renal interstitial hemosiderin Hemosiderin is an iron-containing, golden-brown, granular pigment derived from ferritin, the initial iron-storage protein. As iron accumulates within the cell, aggregates of ferritin molecules form hemosiderin. Upon hemolysis of red blood cells, hemoglobin alpha-beta dimers are released that, if unbound to haptoglobin, are filtered by the glomerulus and appear in the urine as hemoglobinuria. The hemoglobin dimers are taken up by renal proximal tubular cells and degraded and the free chelatable iron is stored as hemosiderin in the lysosomes. Hemosiderin deposition in kidney tubular cells has been reported in different types of hemolytic anemia including autoimmune hemolytic anemia and paroxysmal nocturnal hemoglobinuria and sickle cell anemia and after cardiac valve replacement with residual valvular regurgitation or perivalvular leak. Deposition of hemosiderin (a golden-brown, granular pigment derived from ferritin) in interstitial cells of the kidney. Renal interstitial deposits