present in 70% of homozygotes, and an extended ancestral A candidate gene (HFE) has been described for hereditary haplotype including HLA-A3 and other DNA markers on hemochromatosis on chromosome 6. The study of well-dechromosome 6 has been reported. [5][6][7] A candidate gene has fined atypical hemochromatosis families using genetic markbeen described (HFE), 4.5 Mb telomeric to HLA-A. 8 The use ers may increase our understanding of the sensitivity and the of haplotype analysis and the search for recombinations in specificity of genotyping in hemochromatosis. One hundred families are considered to be powerful tools for localizing a and thirteen Canadian families with genetic hemochromatosis gene responsible for a disease. However, in hemochromatowere surveyed to find atypical families as possible examples sis, it had been difficult to prove informative genetic recombiof people with genetic recombinations. All families underwent nations for several reasons: 1) the late presentation of the clinical investigations including iron studies and HLA typing.probands in the fifth or sixth decade often means that parenEach individual was typed at three polymorphic microsatellite tal DNA is not available; 2) ascertainment of the phenotypic loci (D6S105, D6S1260, and D6S299) on chromosome 6. Sixstatus may be difficult and may vary between studies; and teen subjects were studied for the two missense mutations 3) lack of heterogeneity with available DNA markers has described for the candidate gene for hemochromatosis reduced the number of informative family studies. In this (C282Y, H63D). There were eight HLA-identical siblings study, 113 Canadian families with genetic hemochromatosis found in four different families (five men, three women; age were reviewed, and DNA studies are presented in 5 atypical range 30-72) with normal transferrin saturation and ferritin families with potential recombinations. levels. There were two patients identified who were homozy-
PATIENTS AND METHODS gous for the C282Y mutation without biochemical evidenceA database of 113 Canadian families that had been investigated of iron overload, and two patients with no evidence of the by family studies was reviewed to search for families with potential mutation with significant iron overload. Our conclusions are genetic recombinations. All families were white with European anas follows: 1) finding HLA-identical siblings without iron overcestry. This study included 4 families in which one or more HLAload does not confirm a genetic recombination, 2) difficulties identical sibling was found without phenotypic expression of the in phenotypic definition of disease and the description of new disease, and 1 family in which two putative homozygotes produced iron overload syndromes that may differ from classical genetic an unaffected son. The diagnosis of hemochromatosis was based HC cause complicated genetic studies, and 3) finding iron-on clinical history, physical examination, and elevated serum ferriloaded patients without a C282Y mutation and patients that tin...