title: The clinical relevance of compound heterozygosity for the C282Y and H63D substitutions in hemochromatosis.
abstract: OBJECTIVE
  Two major mutations are defined within the hemochromatosis gene, HFE. Although the effects of the C282Y substitution have been well characterized, the clinical significance of the C282Y/H63D state remains unclear. This study assessed the phenotypic expression in C282Y/H63D subjects as compared with C282Y homozygotes.
  
  
  METHODS
  Data were obtained from 91 C282Y/H63D probands, 158 C282Y/H63D subjects identified through family screening, and 483 C282Y homozygotes. Subjects underwent clinical evaluation, genotyping, biochemical assessment, and liver biopsy examination where clinically indicated.
  
  
  RESULTS
  C282Y/H63D probands had significantly less clinical and biochemical expression than C282Y homozygotes. Biochemical expression was higher in C282Y/H63D probands than in C282Y/H63D subjects identified through family screening (P < .001). Of the C282Y/H63D subjects with serum ferritin levels greater than 1000 mug/L, all had known comorbid factors that could have contributed to the increased ferritin level. Of the 51 C282Y/H63D subjects who underwent liver biopsy examination, significantly increased iron stores were present in 9 subjects and hepatic fibrosis was present in 13. Twelve of the 13 had evidence of hepatic steatosis, excess alcohol consumption, or diabetes. The mobilizable iron level was significantly higher in C282Y homozygous males than in compound heterozygous males (P < .001). Genetic screening of C282Y/H63D first-degree relatives detected 5 C282Y homozygotes.
  
  
  CONCLUSIONS
  C282Y/H63D subjects referred for assessment had a high prevalence of increased iron indices but did not develop progressive clinical disease without comorbid factors such as steatosis, diabetes, or excess alcohol consumption. When fibrosis was seen, 1 or more comorbid factors almost always were present. Thus, phlebotomy therapy is warranted and cascade screening of relatives should be performed because expressing C282Y homozygotes may be detected.
authors.affiliation: The Department of Gastroenterology & Hepatology, Royal Brisbane & Women's Hospital, Brisbane, Australia.
authors.forename: Alissa
authors.initials: A
authors.lastname: Walsh
authors.forename: Jeannette L
authors.initials: JL
authors.lastname: Dixon
authors.forename: Grant A
authors.initials: GA
authors.lastname: Ramm
authors.forename: David G
authors.initials: DG
authors.lastname: Hewett
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Lincoln
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Anderson
authors.forename: V Nathan
authors.initials: VN
authors.lastname: Subramaniam
authors.forename: Julian
authors.initials: J
authors.lastname: Dodemaide
authors.forename: Juleen A
authors.initials: JA
authors.lastname: Cavanaugh
authors.forename: Mark L
authors.initials: ML
authors.lastname: Bassett
authors.forename: Lawrie W
authors.initials: LW
authors.lastname: Powell
mesh_terms: D000328:Adult; D015897:Comorbidity; D018450:Disease Progression; D005260:Female; D005293:Ferritins / Q000097:blood; D006432:Hemochromatosis / Q000097:blood / Q000453:epidemiology / Q000235:genetics*; D000071020:Hemochromatosis Protein; D006579:Heterozygote; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D007501:Iron / Q000378:metabolism; D008099:Liver / Q000737:chemistry; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D010641:Phenotype
chemical_list: C103673:HFE protein, human; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D005293:Ferritins; D007501:Iron