Background and objectives: In Italy, typical HFE mutations account for only 64% of the cases with overt hereditary hemochromatosis (HH), and a common HFE-unrelated disease was hypothesized.
Design and methods: One thousand and fifty potential blood donors were screened by iron tests, C282Y and H63D HFE mutation analysis in a region in North Italy. Subjects with repeated fasting transferrin saturation of 45% or more and no secondary iron overload were defined as probands with idiopathic iron overload. To assess the inheritance of iron overload, relatives of probands were screened.
Results: The overall frequency of probands with idiopathic iron overload was 3.43% (95% confidence interval, 2.32 to 4.52). Of these, 8.4% had genotypes associated with HH (compound heterozygous for H63D/C282Y or homozygous for H63D HFE mutations), and 91.6% had atypical genotypes: 47.2% were heterozygous for C282Y or H63D HFE mutations, and 44.4% had wild type/wild type genotype. A family history of iron overload was proven in 33.3% of probands with atypical genotypes (1.04% of the overall population). Pedigree analysis excluded linkage of heterozygous HFE mutations with iron overload (cumulative lod score 2.41) and documented a recessive non-HLA-linked locus accounting for iron overload in wild type/wild type genotypes. None of the probands had clinical signs of iron accumulation; in males, serum ferritin positively correlated with age (r=0.63, p<0.01), and the regression model predicted a serum ferritin of 700 ng/mL at the age of 58.
Interpretation and conclusions: In Northern Italy an HFE-unrelated, mild idiopathic iron overload is highly prevalent. A recessive locus accounts for iron overload in at least 1.04% of the overall population.