Primary Non-HFE Hemochromatosis: A Review

Abstract

Iron homeostasis is a complex process in which iron uptake and use are tightly balanced. Primary Type 1 or HFE hemochromatosis results from homozygous mutations in the gene that encodes human homeostatic iron regulator (known as human factors engineering, HFE) protein, a regulator of hepcidin, and makes up approximately 90% of all hemochromatosis cases. However, four types of hemochromatosis do not involve the HFE gene. They are non-HFE hemochromatosis type 2A (HFE2, encoding HJV), type 2B (HAMP, encoding hepcidin), type 3 (TFR2, encoding transferring receptor-2), and types 4A and B (SLC40A1, encoding ferroportin. NonHFE hemochromatosis is extremely rare. Pathogenic allele frequencies have been estimated to be 74/100,000 for type 2A, 20/100,000 for type 2B, 30/100,000 for type 3, and 90/100,000 for type 4 hemochromatosis. Current guidelines recommend that the diagnosis be made by ruling out HFE mutations, history, physical examination, laboratory values (ferritin and transferrin saturation), magnetic resonance or other imaging, and liver biopsy if needed. While less common, non-HFE hemochromatosis can cause iron overload as severe as the HFE type. In most cases, treatment involves phlebotomy and is successful if started before irreversible damage occurs. Early diagnosis and treatment are important because it prevents chronic liver disease. This review updates the mutations and their pathogenetic consequences, the clinical picture, diagnostic guidelines, and treatment of hemochromatosis.