The penetrance of hereditary hemochromatosis.

Since its original description as a rare disease of iron overload resulting in liver disease, diabetes mellitus, and bronzing of the skin ('bronze diabetes'), hereditary hemochromatosis has undergone several redefinitions leading to widely varying estimates of its prevalence. Over the last decade, the finding of a relatively high prevalence of the C282Y polymorphism of the HFE gene associated with hemochromatosis in Northern European populations suggested that the disease may be much more common than previously thought. However, several large population-based studies have now shown that the penetrance of the C282Y/C282Y genotype is very low, indicating that C282Y homozygosity is a necessary but not sufficient factor in causation of the disease. Studies are now focusing on other genetic and environmental factors, including alcohol, that may contribute to differential expression of C282Y homozygosity.