Penetrance of HFE haemochromatosis variants to clinical disease: polygenic risk score associations in UK Biobank

BackgroundThe iron overload condition Hereditary Heamochromatosis (HH) can cause liver cirrhosis and cancer, diabetes and arthritis. In Europeans, most HH disease occurs in male HFE p.C282Y homozygotes, yet only a minority of homozygotes in the general population develop these conditions. We aimed to determine whether common genetic variants influencing iron levels or risks for liver, diabetes or arthritis diagnoses in the general population also modify clinical penetrance in HFE p.C282Y and p.H63D carriers.Methods1,294 male and 1,596 female UK Biobank European-ancestry HFE p.C282Y homozygous participants with electronic medical records up to 14 years after baseline assessment were studied. Polygenic risk scores (PRS) quantified genetic effects on blood iron biomarkers and relevant diseases (identified in the general population). Analyses were repeated in 10,699 p.C282Y/p.H63D compound heterozygotes.ResultsIn male p.C282Y homozygotes, higher iron PRS increased risk of liver fibrosis or cirrhosis diagnoses (top 20% of iron PRS had Odds Ratio 4.90: 95% Confidence Intervals 1.63 to 14.73, p=0.005 versus bottom 20%), liver cancer, and osteoarthritis, but not diabetes. The liver cirrhosis PRS also associated with increased liver cancer diagnoses, and greater type-2 diabetes PRS increased risk of type-2 diabetes. In female p.C282Y homozygotes, osteoarthritis PRS was associated with increased osteoarthritis diagnoses, and type-2 diabetes PRS with type-2 diabetes. However, the iron PRS was not robustly associated with diagnoses in p.C282Y homozygote females, or in other p.C282Y/p.H63D genotypes.ConclusionsHFE p.C282Y homozygote penetrance to clinical disease in a large community cohort was partly explained by common genetic variants that influence iron and risks of related diagnoses in the general population. Including PRS in HH screening and diagnosis may help in estimating prognosis and treatment planning.Lay SummaryTwo or three sentences summarizing the main message of the article expressed in plain English to describe your findings to a non-medical audience.Hereditary Haemochromatosis, an iron overload condition, is the most common genetic disease in Northern Europeans; 1 in 150 people carry two copies of the highest risk mutation (called HFE p.C282Y).Only a minority of those with high risk HH variants actually develop iron overload diseases, such as liver cancer, cirrhosis, diabetes and arthritis. We tested whether known genetic variants with smaller effects on iron levels in the whole population modify risk of iron overload related disease in those with the HH high risk variants. We did similar tests for variants linked to each of the diseases caused by iron overload.Increased genetic risk for higher iron significantly raised the likelihood of liver fibrosis, cirrhosis and cancer in mutation carriers. In the future this information could help identify at-risk haemochromatosis patients early.