Iron overload syndromes

Iron overload is relatively common and is now detected more frequently because of inclusion of serum iron measurement in automated clinical chemistry panels. Secondary hemosiderosis and hemochromatosis result from increased iron absorption associated with increased erythropoiesis compensating for hemolysis, increased dietary iron, inappropriate prolonged oral iron therapy or chronic multiple transfusions. Primary hemochromatosis is a genetic metabolic disorder associated with the HLA locus on chromosome 6 resulting in increased iron absorption, though erythropoiesis and dietary iron are normal, and abnormal diversion of iron from reticuloendothelial (RE) to parenchymal cells. A genetic increase of intracellular iron carrier is a proposed basic mechanism. Only in the cirrhotic stage of primary hemochromatosis do RE iron and serum ferritin increase. Since both serum iron and serum ferritin may remain normal in the precirrhotic stage and may be falsely positive in the absence of iron overload, direct measurement of body iron stores is often useful. Measurement of tissue iron in liver biopsy specimens is widely used. However, quantitation of total mobilizable body iron by measurement of a 6-hour urine collection after intravenous injection of 59Fe-DTPA is noninvasive, sensitive, relatively accurate, and together with other laboratory and clinical data provides a practical means of establishing the correct diagnosis and therapy early enough to minimize organ damage.