hemosiderosis

Hemosiderosis is the accumulation of hemosiderin, an iron-storage pigment derived from ferritin, in tissues. It denotes iron deposition that often follows prior bleeding or iron overload, but does not by itself imply widespread tissue destruction. When iron overload is extensive and tissue damage occurs, the condition is often described within the spectrum of iron overload disorders such as hemochromatosis; however, hemosiderosis refers specifically to the pigment deposition.

Forms and causes: Local or focal hemosiderosis results from repeated microhemorrhages or local tissue injury, as seen in pulmonary hemosiderosis after alveolar hemorrhage, or siderosis at sites of prior injections or infections. Systemic (secondary) hemosiderosis describes iron deposition due to overall iron excess from transfusions (as in thalassemia or other anemias), chronic liver disease with increased iron absorption, or other causes of iron overload. Hereditary hemochromatosis is a genetic iron-overload disorder that can lead to widespread tissue siderosis, but it is usually categorized separately from simple hemosiderosis.

Sites and clinical features: Common deposition sites include the lungs (leading to alveolar macrophages loaded with iron), liver, spleen, pancreas, and heart. Clinically, hemosiderosis may be asymptomatic or contribute to organ dysfunction depending on the extent and location of iron deposition. Pulmonary involvement can cause cough and dyspnea; hepatic siderosis may progress to liver disease; cardiac siderosis can affect myocardial function.

Diagnosis: Confirmation relies on tissue staining for iron, typically with Prussian blue. Imaging and laboratory tests support assessment of iron overload, including ferritin levels and transferrin saturation, along with patient history of hemorrhage or transfusion.

Treatment and prognosis: Management targets the underlying cause. For systemic iron overload, therapeutic phlebotomy is used when possible, or iron chelation therapy (eg, deferoxamine, deferasirox, deferiprone). Addressing ongoing bleeding and monitoring organ function are important. Prognosis varies with the extent of iron deposition and the effectiveness of treatment.