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However, HFE is only part of the story, since many patients with mutated HFE do not manifest clinical iron overload, and some patients with iron overload have a normal HFE genotype. A possible explanation is the fact that HFE normally plays a role in the production of hepcidin in the liver, a function that is impaired in HFE mutations. [49]
Majority of the cases of hemochromatosis are caused by mutations in the HFE (Homeostatic Iron Regulator) gene. [17] Type 3 HH is characterized by compound heterozygote mutations in both transferrin receptor 2 (TFR2) and HFE, i.e. a single mutation in each gene. HFE is located on chromosome 6 and TFR2 is located on chromosome 7.
[20] [21] The homozygous H63D variant is an indicator of the iron metabolism disorder hemochromatosis, which may increase the risk of developing a fatty liver. [22] In patients with a cirrhotic liver, the mutation can increase the rate of liver cancer. [6] [23] [24]
Type 4 hemochromatosis is caused by mutations of the SLC40A1 gene, located on the long arm of chromosome 2, specifically at 2q32.2. The SLC40A1 gene encodes ferroportin, a protein responsible for exporting iron from cells in the intestine, liver, spleen, and kidney, as well as from reticuloendothelial macrophages and the placenta.
At least 42 mutations involving HFE introns and exons have been discovered, most of them in persons with hemochromatosis or their family members. [25] Most of these mutations are rare. Many of the mutations cause or probably cause hemochromatosis phenotypes, often in compound heterozygosity with HFE C282Y.
Iron overload (also known as haemochromatosis or hemochromatosis) is the abnormal and increased accumulation of total iron in the body, leading to organ damage. [1] The primary mechanism of organ damage is oxidative stress, as elevated intracellular iron levels increase free radical formation via the Fenton reaction.
In such cases the iron stores of an adult may reach 50 grams (10 times normal total body iron) or more. The most common diseases of iron overload are hereditary hemochromatosis (HH), caused by mutations in the HFE gene, and the more severe disease juvenile hemochromatosis (JH), caused by mutations in either hemojuvelin (HJV) [46] or hepcidin ...
An additional aggravating mutation affecting variegate porphyria can be found at 6p21.3 on the HFE gene. [7] A 2006 clinical, biochemical and mutational study of eight Swiss variegate porphyria patients and their families found four novel PPOX gene mutations believed to be unique to the Swiss population. [8]