IGHG3 and hemochromatosis: In a subsequent report, subnormal levels of IgG subclass 1 (IgG1), IgG3, or IgG1/IgG3 based on 1996 consensus guidelines [9] were common in 51 referred hemochromatosis probands with p.C282Y homozygosity [10] and there was concordance of Ig and hemochromatosis TS/SF phenotypes in probands and their HLA-identical siblings [10].