The HFE gene has three often observed genetic variants:
rs1799945, c.187C>G, p.His63Asp (H63D);
rs1800562, c.845G>A, p. Cys282Tyr (C282Y);
rs1800730, c.193A>T, p.Ser65Cys (S65C).The worldwide prevalence rates for H63D, C282Y and S65C (minor allele frequencies) are 10%, 3% and 1% respectively.The C282Y allele is a transition point mutation from guanine to adenine at nucleotide 845 in HFE, resulting in a missense mutation that replaces the cysteine residue at position 282 with a tyrosine amino acid. Heterozygotes for either allele can manifest clinical iron overload, if they have two of any alleles. This makes them compound heterozygous for haemochromatosis and puts them greatly at risk of storing excess iron in the body. Homozygosity for the C282Y genetic variant is the most common genotype responsible for clinical iron accumulation, though heterozygosity for C282Y/H63D variants, so-called compound heterozygotes, results in clinically evident iron overload. Considerable debate exists regarding the penetrance—the probability of clinical expression of the trait given the genotype— for clinical disease in homozygotes. Most males homozygous for HFE C282Y show at least one manifestation of iron-storage disease by middle age. Individuals with the relevant genetic variants may never develop iron overload. Phenotypic expression is present in 70% of C282Y homozygotes with less than 10% going on to experience severe iron overload and organ damage. The H63D variant is just a gene polymorphism, and if there are no other changes, it may not have clinical significance. In a 2014 study, H63D homozygosity was associated with an elevated mean ferritin level, but only 6.7% had documented iron overload at follow-up.
Finally, several groups reported their findings in a series of patients with haemmochromatosis where they discovered the existence of the C282Y mutation in about 85-90% of the cases. The discovery has led to improved clinical medicine and liver disease evaluation. References
External links
GeneReview/NIH/UW entry on HFE-Associated Hereditary Hemochromatosis
Hereditary haemochromatosis at Curlie