A genotypic study of 217 unrelated probands diagnosed as "genetic hemochromatosis" on "classical" phenotypic criteria

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Abstract

Background/Aims:

The HFE gene is a crucial candidate gene for hemochromatosis. The aims of this study were to assess the HFE genotypic profile in a large series of unrelated probands diagnosed as having phenotypic hemochromatosis, to characterize the subgroup of patients who were not homozygous for the major C282Y mutation, and to report the iron status of the detected HFE-identical siblings.

Methods:

In 217 patients, the phenotypic diagnosis of hemochromatosis was based on strict bioclinical and/or histological criteria, and their genotypic profile (C282Y and H63D mutations) was determined.

Results:

1) 209 of the 217 probands were C282Y+/+. In 33 cases, an HFE-identical sibling was identified. Two of them had neither a clinical nor a biochemical phenotypic profile of hemochromatosis in the absence of any external factor which might have attenuated this expression. 2) Eight patients (seven males) were not C282Y+/+. Their genotypic profiles were: (C282Y+/−): six cases (four were H63D+/− and two H63D−/−); (C282Y−/−): two cases (one was H63D+/+, one H63D+/−). Phenotypic expression consisted of six cases of mild liver siderosis (among whom were the four compound heterozygotes and one case of alcoholic cirrhosis) and two severe cases of hepatic iron overload (one with alcoholic cirrhosis). Three HFE-identical siblings were identified, none of them presenting with iron excess.

Conclusions:

In our population: 1) The classical phenotypic criteria fitted, in 96.3% of cases, with a homogeneous genotypic entity defined by homozygosity for the C282Y mutation. Incomplete penetrance of the homozygous status was shown by the absence of the hemochromatosis phenotypic profile in 6% of the HFE-identical siblings. 2) A minority (3.7%) were not homozygous for C282Y. These were essentially men with mild iron overload, and might present with distinct iron overload entity(ies) as suggested by the presence in three of an HFE-identical sibling with absence of iron overload.

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