Type I Haemochromatosis: What About The C282y/H63d Genotype?

Type I haemochromatosis: What about the C282Y/H63D genotype?Characterised by an iron overload, type I haemochromatosis (classic haemochromatosis) is a complex genetic disease particularly frequent in northern European populations. It is principally associated with the C282Y/C282Y genotype of the HFE gene. A second genotype C282Y/H63D has mostly been described in patients not homozygous for C282Y, but the association of this composite genotype with the disease is highly debated. The objective of this study was to determine the weight of this genotype in patients treated by phlebotomy in a French Blood Agency health centre in Brest. Of 326 patients treated from 2004 through 2007,172 were C282Y/C282Y and 59 C282Y/H63D. The C282Y/H63D group included a higher proportion of men (71.2 versus 55.8%, p = 0.0377) and was diagnosed later (56.9 versus 49.2 years, p < 0.0001) than the C282Y/C282Y patients. The C282Y/H63D genotype was also associated with a milder degree of iron overload, translated by a lower median transferrin saturation coefficient (52.0 versus 84.0%, p < 0.0001) and a smaller median amount of iron removed (2.1 versus 3.6 g, p < 0.0001), despite median serum ferritin were similar. Environmental factors were also significantly more frequent in C282Y/H63D patients (excessive alcohol consumption: 27.5 versus 13.9%, p = 0.0252; overweight: 67.3 versus 39.4%, p = 0.0003). Moreover, if the impact of the C282Y/H63D genotype was comparable to that of the C282Y/C282Y genotype, we should have observed it 14 times more frequently in our study population (OR = 0.07 [0.03-0.18], p < 0.0001). This study confirms the very relative weight of the C282Y/H63D genotype in the occurrence of iron overload and the predominant role of comorbid factors.