Prevalence of HFE C282Y and H63D in Jewish populations and clinical implications of H63D homozygosity

Transient elevation of serum ferritin in a Sri Lankan with homozygosity for H63D mutation in the HFE gene: a case report

INTRODUCTION

Hereditary hemochromatosis is an inherited disorder of iron metabolism, characterized by excessive iron deposition in major organs of the body, leading to multi-organ dysfunction. It is a genetically heterogeneous disease caused by mutations in one or more different genes, the most common being mutations in the HFE gene. HFE hereditary hemochromatosis is mostly found in Europeans and is almost always a result of two mutations: C282Y and H63D. The H63D mutation is not as penetrant as the C282Y mutation, but there are rare reported cases of hereditary hemochromatosis with homozygous H63D genotype. While the C282Y mutation is primarily confined to persons of Northern European origin, the H63D mutation is spread worldwide. Other types of hereditary hemochromatosis are rare and broadly defined as non-HFE hereditary hemochromatosis and include mutations in the hemojuvelin gene, hepcidin (HAMP gene), transferrin receptor 2 gene, and ferroportin gene. Hereditary hemochromatosis is commonly found in populations of European origin; in contrast, it is rare and less well understood in Asia. It can be masked by the presence of concurrent iron deficiency or secondary iron overload in thalassemias.

CASE PRESENTATION

We report the case of a 42-year-old Sri Lankan man investigated for fatigue during a brief upper respiratory tract infection and found to have high liver transaminases and high serum ferritin, which persisted even after complete resolution of the infection. Homozygosity for H63D mutation in the HFE gene was detected. Liver enzymes, serum ferritin, and transferrin saturation normalized following venesections.

CONCLUSION

This case adds to the literature on the importance of being vigilant and investigating patients suspected for iron overload, including genetic studies for hereditary hemochromatosis, even though it is a rare clinical entity in Asians.

C282Y/H63D hemochromatosis mutations and microevolution: Speculations concerning the Basque population

The Basques live at the Western extremity of the Pyrenees. According to linguistic and genetic data they could be considered as one of the most ancient European populations. Numerous studies have evidenced particular patterns in the frequency of several genetic polymorphisms in this relatively unmixed human group. We discuss herein the puzzling distribution of the two major hemochromatosis HFE mutations associated with hereditary hemochromatosis. Thus, one can observe a low frequency of C282Y and, in contrast, one of the highest European frequencies of H63D. Genetic drift (enhanced by the long history and the small size of this population), long persistence of Paleolithic iron-rich diet, lower exposure to major infectious threats and limited mixing with both Celts and Vikings (who demonstrate the highest prevalence of C282Y) could be the underlying factors explaining these particular genetic features. Historical and environmental data represent key elements for understanding the role of the different evolutionary forces which shape the genetic profile of human populations.

Haemochromatosis Gene (HFE) Polymorphisms and Migraine: An Association Study

Several studies have suggested that iron metabolism may be involved in the pathogenesis of migraine. Using a case-control design, we performed an association study in a cohort of Italian migraine patients to evaluate whether a particular allele or genotype of the haemochromatosis gene ( HFE) would modify the occurrence and clinical features of the disease. We genotyped 256 migraine patients and 237 healthy age-, sex- and ethnicity-matched controls for the C282Y and H63D polymorphisms of the HFE gene. Phenotype and allele frequencies of both polymorphisms were similarly distributed in migraine patients and controls. The patients carrying the DD genotype of the H63D polymorphism showed a later age at onset of the disease and an increased number of migraine attacks. Our data suggest that the HFE gene is not a major disease gene for migraine. However, the H63D polymorphism of the HFE gene may be considered a modifying genetic factor in migraine.

EMQN best practice guidelines for the molecular genetic diagnosis of hereditary hemochromatosis (HH)

Molecular genetic testing for hereditary hemochromatosis (HH) is recognized as a reference test to confirm the diagnosis of suspected HH or to predict its risk. The vast majority (typically >90%) of patients with clinically characterized HH are homozygous for the p.C282Y variant in the HFE gene, referred to as HFE-related HH. Since 1996, HFE genotyping was implemented in diagnostic algorithms for suspected HH, allowing its early diagnosis and prevention. However, the penetrance of disease in p.C282Y homozygotes is incomplete. Hence, homozygosity for p.C282Y is not sufficient to diagnose HH. Neither is p.C282Y homozygosity required for diagnosis as other rare forms of HH exist, generally referred to as non-HFE-related HH. These pose significant challenges when defining criteria for referral, testing protocols, interpretation of test results and reporting practices. We present best practice guidelines for the molecular genetic diagnosis of HH where recommendations are classified, as far as possible, according to the level and strength of evidence. For clarification, the guidelines' recommendations are preceded by a detailed description of the methodology and results obtained with a series of actions taken in order to achieve a wide expert consensus, namely: (i) a survey on the current practices followed by laboratories offering molecular diagnosis of HH; (ii) a systematic literature search focused on some identified controversial topics; (iii) an expert Best Practice Workshop convened to achieve consensus on the practical recommendations included in the guidelines.

Ancestral association between HLA and HFE H63D and C282Y gene mutations from northwest Colombia

A significant association between HFE gene mutations and the HLA-A*03-B*07 and HLA-A*29-B*44 haplotypes has been reported in the Spanish population. It has been proposed that these mutations are probably connected with Celtic and North African ancestry, respectively. We aimed to find the possible ancestral association between HLA alleles and haplotypes associated with the HFE gene (C282Y and H63D) mutations in 214 subjects from Antioquia, Colombia. These were 18 individuals with presumed hereditary hemochromatosis (“HH”) and 196 controls. The HLA-B*07 allele was in linkage disequilibrium (LD) with C282Y, while HLA-A*23, A*29, HLA-B*44, and B*49 were in LD with H63D. Altogether, our results show that, although the H63D mutation is more common in the Antioquia population, it is not associated with any particular HLA haplotype, whereas the C282Y mutation is associated with HLA-A*03-B*07, this supporting a northern Spaniard ancestry.

Iron overload is rare in patients homozygous for the H63D mutation

BACKGROUND

Previous research has suggested that the H63D HFE mutation is associated with elevated iron indexes. However, the true penetrance of this mutation remains unclear.

OBJECTIVE

To assess the proportion of H63D homozygotes with laboratory abnormalities consistent with iron overload.

METHODS

The present study was a retrospective analysis of all individuals referred for HFE genotyping in Newfoundland and Labrador between 1999 and 2009, who were found to be homozygous for the H63D mutation. Using electronic health records, results of ferritin, transferrin saturation, aspartate aminotransferase and alanine aminotransferase testing performed closest to the time of genetic testing were recorded for each patient. Iron overload was classified using previously published definitions from the HealthIron study. SPSS version 17.0 (IBM Corporation, USA) was used for descriptive statistics and to compare means using one-way ANOVA.

RESULTS

Between 1999 and 2009, 170 individuals tested positive for H63D⁄H63D. At the time of genotyping, 28.8% had an elevated mean (± SD) ferritin level of 501±829 μg⁄L and 15.9% had an elevated transferrin saturation of 0.45±0.18. At genotyping, 94 individuals had sufficient data available to classify iron overload status. Only three (3.2%) had documented iron overload while the majority (85.1%) had no evidence of iron overload. Sixty individuals had follow-up data available and, of these, only four (6.7%) had documented iron overload, while 45 (75.0%) had no evidence of iron overload. Only one individual had evidence of iron overload-related disease at genotyping and at follow-up.

CONCLUSIONS

H63D homozygosity was associated with an elevated mean ferritin level, but only 6.7% had documented iron overload at follow-up. The penetrance of the H63D mutation appeared to be low.

EASL clinical practice guidelines for HFE hemochromatosis

Iron overload in humans is associated with a variety of genetic and acquired conditions. Of these, HFE hemochromatosis (HFE-HC) is by far the most frequent and most well-defined inherited cause when considering epidemiological aspects and risks for iron-related morbidity and mortality. The majority of patients with HFE-HC are homozygotes for the C282Y polymorphism [1]. Without therapeutic intervention, there is a risk that iron overload will occur, with the potential for tissue damage and disease. While a specific genetic test now allows for the diagnosis of HFE-HC, the uncertainty in defining cases and disease burden, as well as the low phenotypic penetrance of C282Y homozygosity poses a number of clinical problems in the management of patients with HC. This Clinical Practice Guideline will therefore, focus on HFE-HC, while rarer forms of genetic iron overload recently attributed to pathogenic mutations of transferrin receptor 2, (TFR2), hepcidin (HAMP), hemojuvelin (HJV), or to a sub-type of ferroportin (FPN) mutations, on which limited and sparse clinical and epidemiologic data are available, will not be discussed. We have developed recommendations for the screening, diagnosis, and management of HFE-HC.

Hereditary hemochromatosis: pathophysiology, diagnosis, and management

Hereditary hemochromatosis (HH) is an autosomal recessive genetic disease resulting in inappropriate intestinal iron absorption leading to iron overload and end-organ disease. The disease is most prevalent in white individuals of European descent. The C282Y mutation on the HFE gene accounts for most cases of HH; however, other genetic mutations have been identified. End-organ damage results in cirrhosis, diabetes mellitus, and cardiomyopathy. Therapeutic phlebotomy to deplete excessive iron stores is the standard treatment of HH and results in normal longevity if therapy is initiated before end-organ disease occurs.

H63D homozygotes with hyperferritinaemia: is this genotype, the primary cause of iron overload?

OBJECTIVES

Hereditary haemochromatosis is a disease that affects iron metabolism and leads to iron overload. Homozygosity for the H63D mutation is associated with increased transferrin saturation (TS) and ferritin levels. Our objective was to find out if the homozygosity of H63D mutation was the primary cause of iron overload.

PATIENTS AND METHODS

We studied 45 H63D homozygotes (31 males and 14 females) with biochemical iron overload and/or clinical features of haemochromatosis. The simultaneous detection of 18 known HFE, TFR2 and FPN1 mutations and sequencing of the HAMP gene were performed to rule out the possible existence of genetic modifier factors related with iron overload.

RESULTS

Values of biochemical iron overload, measured as percentage TS and serum ferritin concentration (SF), in our H63D homozygotes were significantly higher in patients than in controls: TS 55 +/- 15% vs. 35 +/- 15% and SF 764 (645-883) microg/L vs. 115 (108-123) microg/L for patients and controls, respectively. These H63D homozygotes presented extreme hyperferritinaemia and no additional mutations in HFE, TFR2, FPN1 and HAMP genes were detected.

CONCLUSIONS

The lack of additional mutations in our H63D homozygotes suggests that this genotype could be the primary cause of iron overload in these patients. Despite our results, we cannot entirely discount the possibility that one or more genetic modifier factor exists, simply because we were unable to find it, although there was a precedent in the HFE gene. Genetic modifier factors have been described for C282Y mutations in the HFE gene, but at the present time they have never been reported in H63D homozygotes.