A targeted approach significantly increases the identification rate of patients with undiagnosed haemochromatosis

Management of human factors engineering-associated hemochromatosis: A 2015 update

This review focuses on the management of iron metabolism and iron overload experienced in the hereditary condition, human factors engineering (HFE)-associated hemochromatosis. Hemochromatosis refers to a group of genetic diseases that result in iron overload; the major one globally is HFE-associated hemochromatosis. The evolution in understanding of the most common form of hereditary hemochromatosis, being the substation of cysteine to a tyrosine at position 282 in the HFE gene, has been extensively studied Novel mutations in both HFE and non-HFE genes have been indicated in this disease which hold significance in its application for the Asia-Pacific region. In conditions with iron overload, the storage of excess iron in various body tissues leads to complications and toxic damage. The most common presenting complaint for this disease is malaise, lethargy and other non-specific symptoms. In order to diagnose hereditary hemochromatosis, there are biochemical, imaging and genetic testing options. Currently, cascade screening of affected families is preferred over population-level screening. The mainstay of treatment is venesection and the appropriate approach to treatment has been consolidated over the years. Recently, the indications for venesection therapy of hemochromatosis have been challenged and are the subject of ongoing research.

Recent advances in hemochromatosis: a 2015 update : a summary of proceedings of the 2014 conference held under the auspices of Hemochromatosis Australia

This review focuses on iron metabolism, the genetics of hemochromatosis, current treatment protocols and various screening methods. Even though the most common form of hereditary hemochromatosis, C282Y gene mutations in the HFE gene, has been extensively studied, novel mutations in both HFE and non-HFE genes have been implicated in this disease. These have important implications for the Asia-Pacific region. In overload, deposition of iron in various body tissues leads to toxic damage. Patients commonly present with non-specific symptoms of malaise and lethargy. Biochemical, imaging and genetic testing can be carried out to confirm diagnosis. Venesection forms the mainstay of treatment and at present cascade screening of affected families is recommended over population-level screening.

Phenotypic expression of a novel C282Y/R226G compound heterozygous state in HFE hemochromatosis: molecular dynamics and biochemical studies

Most adults affected with hereditary hemochromatosis are homozygous for a single point mutation of HFE (p.Cys282Tyr). Apart from the compound heterozygous state for the p.Cys282Tyr mutant and the widespread p.His63Asp variant allele, other rare HFE mutations can be found in trans and may have clinical impact. In the present report we describe the structural and functional consequences of a new mutation, namely the p.Arg226Gly which was inherited in trans with the p.Cys282Tyr allele in a patient affected with a mild iron overload. Because the R226G substitution is located in the vicinity of the normal Cys225S-S282Cys disulfide bond we initially investigated the structure of the variant by molecular dynamics techniques in order to estimate the effect of the mutation on the global structure of HFE domain α3. We found that the solvation free energy, hydrophobicity and formation of salt bridges are slightly modified with the global secondary structure of the α3 domain being conserved. In a previous paper, we demonstrated that the Q283P substitution leads to the loss of the normal Cys225S-S282Cys disulfide bridge. Similar to the Q283P substitution, the R226G substitution does not substitute a residue directly involved in the formation of the disulfide bridge. However, unlike the p.Gln283Pro variant which destroyed the normal disulfide bridge, the R226G mutation does not affect the normal Cys225S-S282Cys bridge. Furthermore based on cell line studies we clearly show that the mutation does not prevent cell surface localization, β2-microglobulin association and binding to transferrin receptor 1. This new compound heterozygous phenotype is very close to those of the C282Y/H63D compound heterozygous patients who display the biochemical hemochromatosis phenotype but with lower body iron stores than C282Y homozygotes. Our results do not exclude unknown genetic and/or metabolic factors that may act synergistically to increase the ferritin level.

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.

Prevalence of genetic haemochromatosis and iron overload in patients attending rheumatology and joint replacement clinics

BACKGROUND & AIMS

Genetic Haemochromatosis (GH) is common in North European and Celtic populations and is associated with arthropathy. We aimed to measure the frequency of the common GH mutations (C282Y and H63D), the carrier frequency of C282Y and markers of iron overload in patients who were referred to our rheumatology and joint replacement clinics.

METHODS

Unselected patients attending these clinics were anonymously tested for the described mutations. Transferrin saturation and serum ferritin were also measured and if elevated, the patients had predictive counselling then named GH mutation testing. The carrier and mutation frequencies were also determined in 340 local controls.

RESULTS

One hundred and sixty-one unselected patients attending these clinics were studied. The C282Y mutation carrier frequency was 1 in 5.2 in patients compared with 1 in 8.1 in controls (p < 0.005). The overall mutation frequencies were similar in patients and controls. One patient was found to be a homozygous for the C282Y mutation and eight were compound heterozygotes. Seven other patients had a raised ferritin, one of whom was a C282Y heterozygote.

CONCLUSION

The C282Y carrier frequency is significantly higher in patients attending rheumatology and joint replacement clinics than in controls. Screening of these patients for GH should be considered.

Hereditary hemochromatosis and diabetes mellitus: implications for clinical practice

Hereditary hemochromatosis (HH) is a genetic condition that can lead to unregulated absorption of iron from the gut with resultant iron overload. The most common form of HH is caused by mutations in the HFE gene, with most cases of HH presenting in patients who are homozygous for the Cys282Tyr mutation. The prevalence of HFE gene mutations in persons of Northern European ancestry is fairly high (0.3-0.7% homozygous and 9-14% heterozygous for the Cys282Tyr mutation), but the penetrance of the disease is considered fairly low and is quite variable. While routine screening of the general population is not recommended, a targeted approach to screening in symptomatic patients and in those with a family member with iron overload is warranted. Untreated, iron overload can lead to considerable morbidity including liver cirrhosis, arthritis and diabetes mellitus, and increased mortality. The pathophysiology of diabetes mellitus in HH is thought to be due primarily to defects in the early insulin response to glucose. An Hfe(-/-) mouse model of HH has demonstrated defects in beta-cell function and beta-cell apoptosis that may be mediated by increased oxidative stress. Fortunately, these defects seem to be reversible if phlebotomy treatment is initiated before the development of cirrhosis or diabetes mellitus in patients. Further research into the long-term effects of treatment on prevention of diabetes mellitus in HH is needed.

Screening for hemochromatosis by measuring ferritin levels: a more effective approach

Because the penetrance of HFE hemochromatosis is low, traditional population screening measuring the transferrin saturation is unlikely to be cost-effective because the majority of subjects detected neither have clinical disease nor are likely to develop it. Three independent studies show that only patients with serum ferritin concentrations more than 1000 microg/L are at risk for cirrhosis, one of the main morbidities of hemochromatosis. Among 29,699 white subjects participating in the Scripps/Kaiser hemochromatosis study, only 59 had serum ferritin levels more than 1000 microg/L; 24 had homozygous mutant or compound heterozygous mutant HFE genotypes. In all but 5 of the other subjects, the causes of elevated ferritin were excessive alcohol intake, cancer, or liver disease. Screening for hemochromatosis with serum ferritin levels will detect the majority of patients who will be clinically affected and may detect other clinically significant disease in patients who do not have hemochromatosis genotypes. Because the ferritin level of the majority of adult homozygotes for HFE mutations does not rise over long periods of time, excluding subjects with serum ferritin levels less than or equal to 1000 microg/L should not result in missed opportunities for early treatment of patients who could benefit.

Reverse cascade screening of newborns for hereditary haemochromatosis: a model for other late onset diseases?

BACKGROUND

Genetic testing can determine those at risk for hereditary haemochromatosis (HH) caused by HFE mutations before the onset of symptoms. However, there is no optimum screening strategy, mainly owing to the variable penetrance in those who are homozygous for the HFE Cys282Tyr (C282Y) mutation. The objective of this study was to identify the majority of individuals at serious risk of developing HFE haemochromatosis before they developed life threatening complications.

METHODS

We first estimated the therapeutic penetrance of the C282Y mutation in people living in la Somme, France, using genetic, demographic, biochemical, and follow up data. We examined the benefits of neonatal screening on the basis of increased risk to relatives of newborns carrying one or two copies of the C282Y mutation. Between 1999 and 2002, we screened 7038 newborns from two maternity hospitals in the north of France for the C282Y and His63Asp (H63D) mutations in the HFE gene, using bloodspots collected on Guthrie cards. Family studies and genetic counselling were undertaken, based on the results of the baby's genotype.

FINDINGS

In la Somme, we found that 24% of the adults homozygous for the C282Y mutation required at least 5 g iron to be removed to restore normal iron parameters (that is, the therapeutic penetrance). In the reverse cascade screening study, we identified 19 C282Y homozygotes (1/370), 491 heterozygotes (1/14) and 166 compound heterozygotes (1/42) in 7038 newborns tested. The reverse cascade screening strategy resulted in 80 adults being screened for both mutations. We identified 10 previously unknown C282Y homozygotes of whom six (four men and two women) required venesection. Acceptance of neonatal screening was high; parents understood the risks of having HH and the benefits of early detection, but a number of parents were reluctant to take the test themselves. Neonatal screening for HH is straightforward. Reverse cascade screening increased the efficiency of detecting affected adults with undiagnosed haemochromatosis. This strategy allows almost complete coverage for HH and could be a model for efficient screening for other late onset genetic diseases.

Recent advances in understanding haemochromatosis: a transition state

Mutations in the hepcidin gene HAMP and the hemojuvelin gene HJV have recently been shown to result in juvenile haemochromatosis (JH). Hepcidin is an antimicrobial peptide that plays a key role in regulating intestinal iron absorption. Hepcidin levels are reduced in patients with haemochromatosis due to mutations in the HFE and HJV genes. Digenic inheritance of mutations in HFE and HAMP can result in either JH or hereditary haemochromatosis (HH) depending upon the severity of the mutation in HAMP. Here we review these findings and discuss how understanding the different types of haemochromatosis and our increasing knowledge of iron metabolism may help to elucidate the host's response to infection.

The 16189 variant of mitochondrial DNA occurs more frequently in C282Y homozygotes with haemochromatosis than those without iron loading

BACKGROUND

Patients with hereditary haemochromatosis (HH) are usually homozygous for the C282Y mutation in the HFE gene. They have variable expression of iron overload and present with a variety of complications, including liver disease, diabetes, arthropathy, fatigue, and cardiomyopathy. The mitochondrial 16189 variant is associated with diabetes, dilated cardiomyopathy, and low body fat at birth, and might contribute to genetic predisposition in further multifactorial disorders. The objective of this study was to determine the frequency of the 16189 variant in a range of patients with haemochromatosis, who had mutations in the HFE gene.

METHODS

Blood DNA was analysed for the presence of the 16189 variant in British, French, and Australian C282Y homozygotes and controls, with known iron status, and in birth cohorts.

RESULTS

The frequency of the mitochondrial 16189 variant was found to be elevated in individuals with haemochromatosis who were homozygous for the C282Y allele, compared with population controls and with C282Y homozygotes who were asymptomatic (42/292 (14.4%); 102/1186 (8.6%) (p = 0.003); and 2/64 (3.1%) (p = 0.023), respectively).

CONCLUSIONS

Iron loading in C282Y homozygotes with HH was exacerbated by the presence of the mitochondrial 16189 variant.