Enrico Rossi

A population-based study of the clinical expression of the hemochromatosis gene

BACKGROUND AND METHODS Hereditary hemochromatosis is associated with homozygosity for the C282Y mutation in the hemochromatosis (HFE) gene on chromosome 6, elevated serum transferrin saturation, and excess iron deposits throughout the body. To assess the prevalence and clinical expression of the HFE gene, we conducted a population-based study in Busselton, Australia. In 1994, we obtained blood samples for the determination of serum transferrin saturation and ferritin levels and the presence or absence of the C282Y mutation and the H63D mutation (which may contribute to increased hepatic iron levels) in 3011 unrelated white adults. We evaluated all subjects who had persistently elevated transferrin-saturation values (45 percent or higher) or were homozygous for the C282Y mutation. We recommended liver biopsy for subjects with serum ferritin levels of 300 ng per milliliter or higher. The subjects were followed for up to four years. RESULTS Sixteen of the subjects (0.5 percent) were homozygous for the C282Y mutation, and 424 (14.1 percent) were heterozygous. The serum transferrin saturation was 45 percent or higher in 15 of the 16 who were homozygous; in 1 subject it was 43 percent. Four of the homozygous subjects had previously been given a diagnosis of hemochromatosis, and 12 had not. Seven of these 12 patients had elevated serum ferritin levels in 1994; 6 of the 7 had further increases in 1998, and 1 had a decrease, although the value remained elevated. The serum ferritin levels in the four other homozygous patients remained in the normal range. Eleven of the 16 homozygous subjects underwent liver biopsy; 3 had hepatic fibrosis, and 1, who had a history of excessive alcohol consumption, had cirrhosis and mild microvesicular steatosis. Eight of the 16 homozygous subjects had clinical findings that were consistent with the presence of hereditary hemochromatosis, such as hepatomegaly, skin pigmentation, and arthritis. CONCLUSIONS In a population of white adults of northern European ancestry, 0.5 percent were homozygous for the C282Y mutation in the HFE gene. However, only half of those who were homozygous had clinical features of hemochromatosis, and one quarter had serum ferritin levels that remained normal over a four-year period.

Validation of the FibroTest Biochemical Markers Score in Assessing Liver Fibrosis in Hepatitis C Patients

BACKGROUND Determining the stage of fibrosis by liver biopsy is important in managing patients with hepatitis C virus infection. We investigated the predictive value of the proprietary FibroTest score to accurately identify significant fibrosis in Australian hepatitis C patients. METHODS Serum obtained from 125 confirmed hepatitis C patients before antiviral therapy was analyzed for haptoglobin, alpha(2)-macroglobulin, apolipoprotein A1, bilirubin, and gamma-glutamyltransferase activity, and the FibroTest score was computed. Liver fibrosis pathology was staged according to a defined system on a scale of F0 to F4. We used predictive values and a ROC curve to assess the accuracy of FibroTest scores. RESULTS The prevalence of significant fibrosis defined by liver biopsy was 0.38. The most useful single test for predicting significant fibrosis was serum alpha(2)-macroglobulin (cutoff value, 2.52 g/L; sensitivity, 75%; specificity, 67%). The negative predictive value of a FibroTest score <0.1 was 85%, and the positive predictive value of a score >0.6 was 78%. Although 33 of the 125 patients had FibroTest scores <0.1 and were therefore deemed unlikely to have fibrosis, 6 (18%) had significant fibrosis. Conversely, of the 24 patients with scores >0.6 who were likely to have significant fibrosis, 5 (21%) had mild fibrosis. Of the 125 patients in the cohort, 57 (46%) could have avoided liver biopsy, but discrepant results were recorded in 11 of those 57 (19%). CONCLUSION The FibroTest score could not accurately predict the presence or absence of significant liver fibrosis.

A population-based study of the biochemical and clinical expression of the H63D hemochromatosis mutation

BACKGROUND & AIMS Two major mutations are defined within the hemochromatosis gene, HFE. Although the effects of the C282Y mutation have been well characterized, the effects of the H63D mutation remain unclear. We accessed a well-defined population in Busselton, Australia, and determined the frequency of the H63D mutation and its influence on total body iron stores. METHODS Serum transferrin saturation and ferritin levels were correlated with the H63D mutation in 2531 unrelated white subjects who did not possess the C282Y mutation. RESULTS Sixty-two subjects (2.1%) were homozygous for the H63D mutation, 711 (23.6%) were heterozygous, and 1758 (58.4%) were wild-type for the H63D mutation. Serum transferrin saturation was significantly increased in male and female H63D homozygotes and heterozygotes compared with wild-types. Serum ferritin levels within each gender were not influenced by H63D genotypes. Elevated transferrin saturation > or = 45% was observed in a greater proportion of male H63D carriers than male wild-types. Male H63D homozygotes (9%) and heterozygotes (3%) were more likely to have both elevated transferrin saturation and elevated ferritin > or = 300 ng/mL than male wild-types (0.7%). Homozygosity for H63D was not associated with the development of clinically significant iron overload. CONCLUSIONS Presence of the H63D mutation results in a significant increase in serum transferrin saturation but does not result in significant iron overload. In the absence of the C282Y mutation, the H63D mutation is not clinically significant.

Complex non-invasive fibrosis models are more accurate than simple models in non-alcoholic fatty liver disease

Background and Aim:  Significant hepatic fibrosis is prognostic of liver morbidity and mortality in non‐alcoholic fatty liver disease (NAFLD); however, it remains unclear whether non‐invasive fibrosis models can determine this end‐point. We therefore compared the accuracy of simple bedside versus complex fibrosis models across a range of fibrosis in a multi‐centre NAFLD cohort.

Genotyping as a diagnostic aid in genetic haemochromatosis.

Background: Two mutations in a newly described gene, HFE, have been proposed as genetic markers for the inherited iron overload disease, genetic haemochromatosis.

Biological Variability and Reference Intervals for Total Plasma Homocysteine

We determined the intra-individual biological variability of plasma homocysteine in 20 healthy subjects. The intra-individual coefficient of variation was relatively low (8·3%), indicating that a single measurement can be used to characterize the average homocysteine concentration. A population study measuring plasma homocysteine and serum folate levels was conducted on serum samples collected from 1109 randomly selected, fasting adults with a wide age range. We determined age- and gender-specific central 0·95 intervals and found that subjects in the highest quartile of serum folate had significantly lower (P = 0·0001) mean plasma homocysteine concentrations than did those in the lowest quartile of folate values. An ‘ideal’ homocysteine reference range, based on targeting those subjects who are likely to be folate replete, is preferable to the population-based range using the central 0·95 interval.

Effects of body iron stores and haemochromatosis genotypes on coronary heart disease outcomes in the Busselton health study

Background Increased iron stores and haemochromatosis gene mutations may be risk factors for coronary heart disease. The aims of this study were to determine in a stable community population whether increased iron stores or haemochromatosis gene mutations were risk factors for coronary heart disease. Design Cross-sectional and prospective cohort studies. Methods We evaluated 1185 men and 1141 women aged 20–79 years of predominantly Anglo-Celtic descent from the 1994–95 assessment of the Busselton population in Western Australia. Subjects underwent haemochromatosis genotyping, serum iron studies, clinical, biochemical and ECG evaluation for coronary heart disease and associated risk factors. Hospital admissions or death from cardiovascular disease were determined by linkage with the Western Australian morbidity and mortality database. The study design was cross-sectional for the 1994–95 cohort comparing coronary heart disease cases with unaffected subjects and unaffected subjects were followed prospectively until December 1998. Results Cross-sectional and prospective cohort analyses demonstrated that elevated serum iron parameters or possession of either the C282Y or H63D mutations in the HFE gene were not predictive of increased risk for coronary heart disease in men or women. Conclusions Increased iron stores or haemochromatosis gene mutations are not significant risk factors for coronary heart disease.

Prevalence, Characteristics, and Prognostic Significance of HFE Gene Mutations in Type 2 Diabetes: The Fremantle Diabetes Study

OBJECTIVE—To examine the relationship between iron status, hereditary hemochromatosis (HFE) gene mutations, and clinical features and outcomes of type 2 diabetes in a well-characterized representative sample of community-based patients. RESEARCH DESIGN AND METHODS—HFE genotype data were available for 1,245 type 2 diabetic patients from the longitudinal observational Fremantle Diabetes Study (FDS), representing 96.2% of the total FDS type 2 diabetes cohort. Data were collected at recruitment between 1993 and 1996 and annually until the end of June 2001. Hospitalization and mortality data were available until the end of June 2006. The presence of the C282Y HFE mutation was determined in all subjects and H63D in C282Y heterozygotes. Fasting serum iron, transferrin, and ferritin were measured in all C282Y homozygotes and C282Y/H63D heterozygotes and in 286 randomly selected wild-type subjects. Multiple logistic regression analysis was performed to determine independent baseline associates of prevalent complications (myocardial infarction, cerebrovascular disease, retinopathy, neuropathy, and nephropathy), as was Cox proportional hazards modeling to determine predictors of incident complications and mortality. RESULTS—Although there were expected positive associations between HFE gene mutations and serum iron and transferrin saturation, there were no independent positive associations between HFE gene status and either microvascular or macrovascular complications in cross-sectional and longitudinal analyses. HFE gene status did not independently predict cardiac or all-cause mortality. Measures of iron metabolism including serum ferritin were not associated with combined microvascular or macrovascular end points. CONCLUSIONS—Directed screening for iron overload and/or HFE mutations appears unwarranted in patients with type 2 diabetes.

Clinical penetrance of C282Y homozygous HFE hemochromatosis

Following the discovery of the HFE gene, it became apparent that C282Y homozygous HFE hemochromatosis is the most common autosomal recessive genetic disorder in populations of northern European descent, where it attains a maximum prevalence of approximately 1 in 200. Cross-sectional studies have revealed that the clinical penetrance of symptoms of iron-loading disease is relatively low and highly variable. Although there is no standard definition of clinical penetrance, large studies of newly diagnosed C282Y homozygotes that have specifically assessed liver disease have obtained data showing that penetrance occurs in between 24 and 43% of males and 1 and 14% of females. This relatively low clinical penetrance is largely unexplained. Current evidence suggests a limited role for digenic inheritance of mutations in iron homeostasis genes in modifying the penetrance of HFE hemochromatosis. Currently, the single most important environmental and genetic variables promoting penetrance are alcohol consumption and male gender, respectively. With genetic analyses becoming simpler to perform, new genetic modifiers of hepatic iron loading and liver fibrogenesis await identification.

Hepatic iron loading in patients with compound heterozygous HFE mutations.

Abstract: Aim: To assess the severity of hepatic iron loading in patients with a compound heterozygous C282Y/H63D HFE genotype.