Hereditary Hemochromatosis / Монголын Анагаах Ухаан

ABSTRACT

Hemochromatosis is a common inherited disorder of iron metabolism in which an inappropriate increase in intestinal iron absorption results in deposition of excessive amounts of iron in parenchymal cells with eventual tissue damage and impaired organ function. The human HFE gene was identified as the most common form of hemochromatosis in 1996. A homozygous G A mutation resulting in a cysteine to tyrosine substitution at position 282 (C282Y) is the most common mutation. It is identified in 85–90% of patients with hereditary hemochromatosis in populations of northern European descent. A second relatively common HFE mutation (H63D) results in a substitution of histidine to aspartic acid at codon 63. Homozygosity for H63D is not associated with clinically significant iron overload. Some compound heterozygotes (e.g., one copy each of C282Y and H63D) have moderately increased body iron stores but develop clinical disease only with cofactors such as heavy alcohol intake or hepatic steatosis. Thus, HFE-associated hemochromatosis is inherited as an autosomal recessive trait; heterozygotes have no, or minimal, increase in iron stores. However, this slight increase in hepatic iron can act as a cofactor that modifies the expression of other diseases such as porphyria cutanea tarda (PCT) and nonalcoholic steatohepatitis. Mutations in other genes involved in iron metabolism are responsible for non-HFE-associated hemochromatosis, including juvenile hemochromatosis, which affects persons in the second and third decade of life. Mutations in the genes encoding hepcidin, transferrin receptor 2 (TfR2), and hemojuvelin result in clinicopathologic features indistinguishable from HFE-associated hemochromatosis. However, mutations in ferroportin, responsible for the efflux of iron from enterocytes and most other cell types, result in iron loading of reticuloendothelial cells and macrophages, as well as parenchymal cells.