A recent study by McLaren et al. identified a sequence variant, D519G (rs11558492), of GNPAT that was associated with a high iron phenotype at presentation in men with hereditary hemochromatosis who were homozygous for HFE C282Y.[10] Further investigations suggested that GNPAT, like HFE, participates in the regulation of hepcidin expression.[10] These observations led us to the hypothesis that, analogous to HFE C282Y and H63D, GNPAT D519G is a risk factor for PCT. This evidence concerns the gene GNPAT and hemochromatosis.