Pathogenesis, Diagnosis and Treatment of Hemochromatosis

Abstract

Hemochromatosis is a common cause of chronic liver disease and HFE genotyping allows decisive and non-invasive diagnosis. Molecular and clinical genetic studies have led to the identification of genes other than HFE in patients with inherited diseases associated with increased hepatic iron storage that can cause hemochromatosis, which adds complexity to a diagnostic approach to patients with suspected hemochromatosis. Despite major advances in genetics, hepatic iron quantification by non-invasive methods therefore remains the key to the diagnosis of hemochromatosis. Although associated with homozygosity for the C282Y polymorphism in the HFE gene in >80% of patients, hemochromatosis is a complex genetic disease with strong environmental disease modifiers. Testing for mutations in the non-HFE hemochromatosis genes transferrin receptor 2, hemojuvelin, HAMP and SLC40A1 is complex, costly and time-consuming. Demonstration of hepatic iron overload by liver biopsy or MRI is therefore required before such complex tests are carried out. The pathogenesis of chronic liver disease in hemochromatosis is mainly attributed to the redox potential of tissue iron, and only the more recent studies have focused on the toxic properties of circulating iron. Considering the fact that an increased saturation of transferrin and high iron in plasma are the hallmark of all hemochromatosis forms, an alternative view would be that toxic iron in the circulation is involved in the pathogenesis of hemochromatosis. Recent studies have shown an increased concentration of redox-active iron in plasma in patients with increased transferrin saturation. This finding supports the hypothesis that tissue iron may be the ‘smoking gun' of iron-induced organ damage. Taken together, caring for patients with suspected or established hemochromatosis still remains a challenge, where understanding the genetics, biochemistry and cell biology of hemochromatosis will aid better diagnosis and treatment of affected individuals.