HLA typing in 67 Italian patients with idiopathic hemochromatosis and their relatives.

The frequency of HLA A3 and B7 antigens was significantly higher in 67 unrelated patients with idiopathic hemochromatosis (IH) than in 700 controls (62.7% vs 22.5%, p less than 10(-8) and 26.9% vs 9.3%, p less than 10(-3), respectively). A3 B7, A3 B35 and A3 B5 were significantly more frequent in 72 haplotypes linked to IH gene than in 278 control haplotypes. The prevalence of B35 and A3 B35 was significantly higher in IH patients from North-Eastern Italy than from other regions (60% vs 21%, p less than .05 and 54.5% vs 8.2%, p less than 0.0001, respectively). All 15 siblings HLA identical to the respective proband were homozygous for IH with variable expression of the disease, whereas minor abnormalities of iron-related indexes were present in 23% of heterozygous relatives. Homozygous-heterozygous mating probably occurred in three of 40 families, accounting for the overt disease in three offspring and in one HLA semi-identical sibling; however, in this last case the possibility of a recombination event cannot be excluded.