Inherited iron loading: genetic testing in diagnosis and management

Iron intake and multiple health outcomes: Umbrella review

Iron is an essential trace element, while excess iron can lead to different levels of physical abnormalities or diseases. This umbrella review aimed to conduct a systematic evaluation of the possible relationships between iron intake and various health outcomes. We retrieved PubMed, Embase, Web of Science, Scopus, and the Cochrane Database of Systematic Reviews from inception through May 2021. A total of 34 meta-analyses with 46 unique health outcomes were identified. Heme iron intake was positively associated with nine outcomes, including colorectal cancer, type 2 diabetes mellitus, and cardiovascular disease mortality, while dietary total iron intake could decrease the risk of colorectal adenoma, esophageal cancer, coronary heart disease, and depression. Iron supplementation was a protective factor against eight outcomes. However, it was associated with decreased length and weight gain. The quality of evidence for most outcomes was "low" or "very low" with the remaining eleven as "high" or "moderate". All outcomes were categorized as class III, IV, or NS based on evidence classification. Although high iron intake has been identified to be significantly associated with a range of outcomes, firm universal conclusions about its beneficial or negative effects cannot be drawn given the low quality of evidence for most outcomes.

Safety and efficacy of supplements in pregnancy

Pregnancy is a time where expectant mothers often focus on their diet to improve their own health and to preserve the future health of their children. There is much conflicting information in the public domain about the safety and/or efficacy of nutritional supplements during pregnancy. Despite this, the market for supplements is growing. This review discusses the roles of critical nutrients in pregnancy and the available evidence on the use of supplements to reduce risks and improve maternal and fetal outcomes. Recommendations are made for pregnant women, taking into account safety data and tolerable upper intakes set for pregnant women. It is important for dieticians, nutritionists, physicians, and other healthcare providers to be able to offer accurate and evidence-based advice on supplement use in pregnancy. Routine supplementation may not be necessary for all, but individuals at risk are identified.

Hemochromatosis (HFE) gene mutations and risk of gastric cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) study

Hereditary hemochromatosis (HH) is a strong risk factor for hepatocellular cancer, and mutations in the HFE gene associated with HH and iron overload may be related to other tumors, but no studies have been reported for gastric cancer (GC). A nested case-control study was conducted within the European Prospective Investigation into Cancer and Nutrition (EPIC), including 365 incident gastric adenocarcinoma and 1284 controls matched by center, sex, age and date of blood collection. Genotype analysis was performed for two functional polymorphisms (C282Y/rs1800562 and H63D/rs1799945) and seven tagSNPs of the HFE genomic region. Association with all gastric adenocarcinoma, and according to anatomical localization and histological subtype, was assessed by means of the odds ratio (OR) and 95% confidence interval (CI) estimated by unconditional logistic regression adjusted for the matching variables. We observed a significant association for H63D with OR (per rare allele) of 1.32 (CI = 1.03-1.69). In subgroup analyses, the association was stronger for non-cardia anatomical subsite (OR = 1.60, CI = 1.16-2.21) and intestinal histological subtype (OR = 1.82, CI = 1.27-2.62). Among intestinal cases, two tagSNPs (rs1572982 and rs6918586) also showed a significant association that disappeared after adjustment for H63D. No association with tumors located in the cardia or with diffuse subtype was found for any of the nine SNPs analyzed. Our results suggest that H63D variant in HFE gene seems to be associated with GC risk of the non-cardia region and intestinal type, possibly due to its association with iron overload although a role for other mechanisms cannot be entirely ruled out.

Unusual presentation of hemochromatosis as isolated metacarpophalangeal joint osteoarthritis: a case report

BACKGROUND

Hemochromatosis, North America's most prevalent genetic disorder, tends to present with an insidious onset and subtle, yet characteristic findings. Patients tend to present with both constitutional symptoms and end-organ effects.

METHODS

Clinical criteria such as history, physical examination, imaging criteria with focused radiologic constellations, and laboratory findings were used for diagnosis.

RESULTS

We report the case of a man who lacked classic systemic symptoms, but instead presented with isolated metacarpophalangeal joint disease and characteristic radiologic findings. The diagnosis was confirmed by serum iron studies and subsequent genetic work-up.

CONCLUSIONS

A high index of clinical suspicion is required to diagnose early disease; better prognostic responses are expected with treatment of less severe disease. Hand surgeons should be aware of the characteristic findings for this rare presentation so proper treatment can be initiated early.

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.

UGT1A1 gene polymorphism as a potential factor inducing iron overload in the pathogenesis of type 1 hereditary hemochromatosis

Aim Hereditary hemochromatosis is a common genetic disorder characterized by iron overload and subsequent organ damage. It is caused in most cases by HFE gene mutations which penetrance can be affected by many factors. The aim of this study was to establish the role of UGT1A1 gene polymorphism and serum bilirubin concentration in the pathogenesis of hereditary hemochromatosis. Methods Biochemical, histopathological and genetic data indicating iron excess and serum total bilirubin concentration were determined in 32 patients with the type 1 hereditary hemochromatosis. Fluorescent molecular probes assays were used for genotyping of UGT1A1*28 and UGT1A1*60 mutations in these individuals. Results High incidence and a significant correlation of UGT1A1 gene mutations with increased serum bilirubin level and lower grades of liver tissue inflammatory activity were observed in study participants. UGT1A1*28 and UGT1A1*60 mutations were strongly linked together. Two of the subjects presented very rare genotypes of UGT1A1 gene: (TA)(5/7) and c.-64G>C heterozygotes. Conclusions UGT1A1 gene polymorphism and as its consequence of high serum bilirubin level may promote iron accumulation in hemochromatosis patients by reducing the activity of inflammation. We proposed a possible mechanism of this interaction.

Iron-overload-related disease in HFE hereditary hemochromatosis

BACKGROUND

Most persons who are homozygous for C282Y, the HFE allele most commonly asssociated with hereditary hemochromatosis, have elevated levels of serum ferritin and transferrin saturation. Diseases related to iron overload develop in some C282Y homozygotes, but the extent of the risk is controversial.

METHODS

We assessed HFE mutations in 31,192 persons of northern European descent between the ages of 40 and 69 years who participated in the Melbourne Collaborative Cohort Study and were followed for an average of 12 years. In a random sample of 1438 subjects stratified according to HFE genotype, including all 203 C282Y homozygotes (of whom 108 were women and 95 were men), we obtained clinical and biochemical data, including two sets of iron measurements performed 12 years apart. Disease related to iron overload was defined as documented iron overload and one or more of the following conditions: cirrhosis, liver fibrosis, hepatocellular carcinoma, elevated aminotransferase levels, physician-diagnosed symptomatic hemochromatosis, and arthropathy of the second and third metacarpophalangeal joints.

RESULTS

The proportion of C282Y homozygotes with documented iron-overload-related disease was 28.4% (95% confidence interval [CI], 18.8 to 40.2) for men and 1.2% (95% CI, 0.03 to 6.5) for women. Only one non-C282Y homozygote (a compound heterozygote) had documented iron-overload-related disease. Male C282Y homozygotes with a serum ferritin level of 1000 mug per liter or more were more likely to report fatigue, use of arthritis medicine, and a history of liver disease than were men who had the wild-type gene.

CONCLUSIONS

In persons who are homozygous for the C282Y mutation, iron-overload-related disease developed in a substantial proportion of men but in a small proportion of women.

HFE gene mutation, chronic liver disease, and iron overload In Turkey

We aimed to determine the relationships between iron overload and HFE gene mutation in chronic liver disease in Turkey. One hundred thirteen chronic liver disease patients and 138 healthy controls were evaluated regarding their clinical, biochemical, and genetic parameters. Each group was divided into two subgroups according to transferrin saturation (TS) (45% and >45%). HFE gene mutation was analyzed by the PCR-RFLP method. C282Y homozygote, heterozygote, and wild-type mutation rates were 1.7%, 0%, and 98.3% in patients and 0%, 1.4%, and 98.6% in controls, respectively. H63D homozygote, heterozygote, and wild-type mutation rates were 1.8%, 24.7%, and 73.5% in patients and 1.4%, 24%, and 74.6% in controls, respectively. Mutation rates were not statistically different in patients with high and normal TS. Iron overload was positively correlated with biochemical activity and Child-Pugh score (P < 0.05). In multivariate analysis, H63D homozygotic mutation was an independent factor for the development of hepatocellular carcinoma (P = 0.004). We conclude that C282Y mutation is very rare in Turkey. Iron overload is not related to H63D mutation but is positively correlated with biochemical activity and Child-Pugh score in chronic liver diseases.

Importance of hereditary haemochromatosis in the care of diabetes mellitus

Szerzők a vas- és a szénhidrátanyagcsere kapcsolatait vizsgálták saját és irodalmi eredmények tükrében. Különös hangsúlyt fektettek a szabad gyökös folyamatok ismertetésére, mivel a hereditaer haemochromatosis és a diabetes mellitus is, mint a vas- és a szénhidrátanyagcsere-zavarok leggyakoribbjai oxidatív stressz keltése révén vezetnek szövődményekhez. A nagy vér és szöveti glükózkoncentráció elektronfelesleget eredményez. Ez redukálhatja a redox ciklusban részt vevő, transzport- vagy raktárfehérjéhez nem kötött vasat, és ez vezet az oxidatív stresszhez. A hereditaer haemochromatosis mind a válogatás nélküli, mind pedig a diabeteses populációban a szöveti redox-aktív vas szintjének emelkedését okozhatja. A hereditaer haemochromatosis leggyakoribb mutációit hordozók aránya hazánkban, szelekció nélküli népességben 30,4%-ot és diabetesben 35,8%-ot tesz ki. Az irodalom adatai szerint feltételezhető, hogy már a hereditaer haemochromatosis leggyakoribb mutációi (HFE-C282Y és HFE-H63D) szempontjából heterozigotákban is megemelkedik a szöveti vasszint, bár a fenotípusban a hereditaer haemochromatosis ilyenkor általában nem jelenik meg, mivel penetranciája alacsony. Mégis, ez a megemelkedett vas-ellátottság a már más okból – például diabetes mellitus miatt – károsodott szövetek betegségének progresszóját okozhatja. Másrészt a hereditaer haemochromatosis olyan endothelkárosodáshoz vezethet, ami miatt – a diabetes mellitus manifesztálódását megelőzően – hypertonia alakulhat ki. Feltételezhető, hogy a vérnyomásemelkedés a hereditaer haemochromatosis egyik legkorábbi klinikai jele. Nehezen beállítható hypertonia és szénhidrátanyagcsere-zavar esetén érdemes gondolni a hereditaer haemochromatosis lehetőségére.

Best practice guidelines for the molecular genetic diagnosis of Type 1 (HFE-related) hereditary haemochromatosis

Background

Hereditary haemochromatosis (HH) is a recessively-inherited disorder of iron over-absorption prevalent in Caucasian populations. Affected individuals for Type 1 HH are usually either homozygous for a cysteine to tyrosine amino acid substitution at position 282 (C282Y) of the HFE gene, or compound heterozygotes for C282Y and for a histidine to aspartic acid change at position 63 (H63D). Molecular genetic testing for these two mutations has become widespread in recent years. With diverse testing methods and reporting practices in use, there was a clear need for agreed guidelines for haemochromatosis genetic testing. The UK Clinical Molecular Genetics Society has elaborated a consensus process for the development of disease-specific best practice guidelines for genetic testing.

Methods

A survey of current practice in the molecular diagnosis of haemochromatosis was conducted. Based on the results of this survey, draft guidelines were prepared using the template developed by UK Clinical Molecular Genetics Society. A workshop was held to develop the draft into a consensus document. The consensus document was then posted on the Clinical Molecular Genetics Society website for broader consultation and amendment.

Results

Consensus or near-consensus was achieved on all points in the draft guidelines. The consensus and consultation processes worked well, and outstanding issues were documented in an appendix to the guidelines.

Conclusion

An agreed set of best practice guidelines were developed for diagnostic, predictive and carrier testing for hereditary haemochromatosis and for reporting the results of such testing.

Heteroduplex analysis for the three common HFE variants: methodology, reliability and analysis of over 5000 requests for testing

OBJECTIVE

To describe the analysis of over 5300 patient samples for the HFE genotype.

METHODS

Blood samples received from hospitals in England, Wales and Ireland were analysed with a single, multiplex PCR using heteroduplex generators for the C282Y, H63D and S65C variants of the HFE gene. PCR products labelled with fluorescent dyes were analysed by capillary electrophoresis. Genotype frequencies were analysed according to the reasons given for testing.

RESULTS

Analysis of 400 samples sent in duplicate revealed one error that was associated with reporting rather than the methodology. Of 5327 samples received, 1122 were for family testing, 2470 for diagnostic testing and in 1735 cases no reason was given. Overall, homozygosity for C282Y was found in 14% of samples received for family testing and in 16% of the remaining samples. Clinical indications such as "liver disease" were of little predictive value for homozygosity for C282Y, but this increased if a raised serum ferritin concentration or transferrin saturation was indicated. When the diagnosis was iron overload, 39% of subjects tested were homozygous for C282Y. Compound heterozygosity (C282Y/H63D) was more frequent than in the general population but the frequency was not further increased in subjects for whom there was a diagnosis of iron overload. The frequencies of heterozygosity for H63D or S65C and homozygosity for H63D were not significantly increased in any group compared with the general population frequency.

CONCLUSION

These results demonstrate the reliability of the methodology and confirm the difficulty of identifying genetic haemochromatosis purely on the basis of clinical suspicion that haemochromatosis may be responsible for liver disease, diabetes or arthritis.

Prevalence of HFE mutations in California newborns

Advances in molecular diagnostics have led to an increased interest in expanding population-based screening to include genetic diseases that occur outside the newborn period. Hereditary hemochromatosis may be a candidate for large-scale screening in populations with a high prevalence of the common HFE mutations. To determine race-specific frequencies of the HFE mutations, C282Y and H63D, the authors applied an automated, high-throughput genotyping method to dried blood spot samples from a representative population of California newborns. In this sample of 3989 newborns, C282Y and H63D allele frequencies were highest in white (C282Y: 5.5 +/- 0.5%; H63D: 13.4 +/- 0.76%) and Hispanic (C282Y: 1.8 +/- 0.29%; H63D: 11.9 +/- 0.72%) newborns, and lowest in black (C282Y: 1.3 +/- 0.25%; H63D: 3.0 +/- 0.38%) and Asian (C282Y 0.5 +/- 0.16%; H63D 2.9 +/- 0.37%) newborns. The estimated prevalence of C282Y homozygotes in this multiracial population is 1.4/1000. As additional genetic and environmental risk factors for HHC are identified, neonatal screening may become an acceptable strategy to follow susceptible individuals and prevent clinical disease.

Targeted screening for genetic haemochromatosis: a combined phenotype/genotype approach

OBJECTIVE

To evaluate the clinical utility of a targeted screening approach for the detection of genetic haemochromatosis.

METHODS

Screening by measuring fasting serum transferrin saturation (TS) and gene testing was carried out in patients in whom a raised serum alanine amino transferase (ALT) activity and raised random serum TS had been found on routine blood testing.

RESULTS

During the 29 month study period, 32 patients homozygous for the C282Y genotype were detected from a catchment population of 330,000 by screening blood samples referred initially for routine laboratory liver function tests. By comparison, during the same period of time and within the same population, only seven patients were found by clinical suspicion alone. The patients in the study, after treatment by venesection, have shown both clinical and biochemical improvement.

CONCLUSIONS

The study shows that from a population of patients in whom a routine liver function profile had been requested, it is possible to detect subjects homozygous for the C282Y HFE genotype who have clinical or biochemical markers of iron overload.

Hereditary iron overload: update on pathophysiology, diagnosis, and treatment

Hereditary hemochromatosis, a very common genetic defect in the Caucasian population, is characterized by progressive tissue iron overload which leads to irreversible organ damage if it is not treated timely. The elucidation of the molecular pathways of iron transport through cells and its control has led to the understanding of various genetic iron-loading conditions. Four types of inherited iron overload have been recognized: type 1, the most common form with an autosomal recessive inheritance, is associated with mutations in the HFE gene on chromosome 6; type 2 (juvenile hemochromatosis) is an autosomal recessive disorder with causative mutations identified in the HJV gene (subtype A) on chromosome 1 and the HAMP gene (subtype B) on chromosome 19; type 3 has also an autosomal recessive inheritance with mutations in the TfR2 gene on chromosome 3; type 4 is an autosomal dominant condition with heterozygous mutations in the ferroportin 1 gene on chromosome 2. In this review, the genetics, pathophysiology, diagnosis, clinical features, and management of these different types of hereditary hemochromatosis are briefly discussed.

The molecular genetics of haemochromatosis

The molecular basis of haemochromatosis has proved more complex than expected. After the 1996 identification of the main causative gene HFE and confirmation that most patients were homozygous for the founder C282Y mutation, it became clear that some families were linked to rarer conditions, first named 'non-HFE haemochromatosis'. The genetics of these less common forms was intensively studied between 2000 and 2004, leading to the recognition of haemojuvelin (HJV), hepcidin (HAMP), transferrin receptor 2 (TFR2) and ferroportin-related haemochromatosis, and opening the way for novel hypotheses such as those related to digenic modes of inheritance or the involvement of modifier genes. Molecular studies of rare haemochromatosis disorders have contributed to our understanding of iron homeostasis. In turn, recent findings from studies of knockout mice and functional studies have confirmed that HAMP plays a central role in mobilization of iron, shown that HFE, TFR2 and HJV modulate HAMP production according to the body's iron status, and demonstrated that HAMP negatively regulates cellular iron efflux by affecting the ferroportin cell surface availability. These data shed new light on the pathophysiology of all types of haemochromatosis, and offer novel opportunities to comment on phenotypic differences and distinguish mutations.