Form Of Hereditary Hemochromatosis Research Articles

A brief communication of patients with homozygous C282Y mutation-related hereditary hemochromatosis.

Hereditary hemochromatosis (HH) is an autosomal recessive inherited iron-loading disorder and is characterized by chronic hepatitis, cirrhosis, diabetes, and bronze skin. The hemochromatosis gene (C282Y homozygosity)-related hemochromatosis is the most common form of HH. The prevalence of HH is varied. Here, we defined six cases with C282Y homozygosity-related HH in a single center in Turkiye.

Appropriate Clinical Genetic Testing of Hemochromatosis Type 2-4, Including Ferroportin Disease.

Hereditary hemochromatosis (HH) is an inherited iron overload disorder due to a deficiency of hepcidin, or a failure of hepcidin to degrade ferroportin. The most common form of HH, Type 1 HH, is most commonly due to a homozygous C282Y mutation in HFE and is relatively well understood in significance and action; however, other rare forms of HH (Types 2–4) exist and are more difficult to identify and diagnose in clinical practice. In this review, we describe the clinical characteristics of HH Type 2–4 and the mutation patterns that have been described in these conditions. We also review the different methods for genetic testing available in clinical practice and a pragmatic approach to the patient with suspected non-HFE HH.

Hepcidin Signaling in Health and Disease: Ironing Out the Details.

Hepcidin, a peptide hormone produced by hepatocytes, is the central regulator of systemic iron homeostasis through its interaction with ferroportin, the major cellular iron export protein. Hepcidin binding to ferroportin results in reduced iron export from macrophages and intestinal absorptive cells, leading to decreased serum iron levels. Hepcidin expression is influenced by several factors that include serum and liver iron stores, erythropoiesis, hypoxia, inflammation, and infection. Erythropoietic drive and hypoxia suppress hepcidin expression and promote red cell production. In contrast, inflammation and infection are associated with increased hepcidin production to sequester iron intracellularly as a means of depriving microorganisms of iron. Chronic inflammation may up‐regulate hepcidin expression through the interleukin‐6 (IL‐6)–Janus kinase 2 (JAK2)–signal transducer and activator of transcription 3 (STAT3) pathway. The bone morphogenetic protein (BMP)–mothers against decapentaplegic homolog (SMAD) pathway is a major positive driver of hepcidin expression in response to either increased circulating iron in the form of transferrin or iron loading in organs. Hereditary hemochromatosis (HH) consists of several inherited disorders that cause inappropriately reduced hepcidin expression in response to body iron stores, leading to increased iron absorption from a normal diet. The most common form of HH is due to a mutation in the HFE gene, which causes a failure in the hepatocyte iron–sensing mechanism, leading to reduced hepcidin expression; the clinical manifestations of HFE‐HH include increased serum transferrin–iron saturation and progressive iron loading in the liver and other tissues over time among patients who express the disease phenotype. In this article, we review the physiologic mechanisms and cellular pathways by which hepcidin expression is regulated, and the different forms of HH resulting from various mutations that cause hepcidin deficiency. We also review other drivers of hepcidin expression and the associated pathophysiologic consequences.

SAT-354 Isolated Hypoparathyroidism: A Rare Initial Manifestation of Hereditary Hemochromatosis (HH)

Background:We present a case of hypoparathyroidism diagnosed in a patient as initial manifestation of hereditary hemochromatosis. As per our literature search, it is very rarely reported as an isolated abnormality in HH.Case:A 27 year old male with history of seizure disorder, well controlled on Oxcarbazepine, referred for evaluation of chronic hypocalcemia. His PMH includes cerebral palsy, with good functional capacity and mild cognitive impairment. He denied muscle spasm, perioral numbness, bone pain, muscle weakness or fracture. He was taking calcium carbonate 600mg bid and vitamin D 50,000 IU q2monthly.There was no family history of any Ca disorders. Physical exam was unremarkable.Laboratory evaluation revealed Ca levels ranging from 7.6 to 8.5mg/dl with intact PTH values ranging from 11 to 22pg/ml. His ionized calcium was also low. Patient’s 24 hr urinary Ca was 122mg/24hrs. In this case, he did initially have hypomagnesemia and vitamin d deficiency, which could potentially explain low calcium. But even after supplementing Vitamin D and Mg, patient’s Ca remained low. His kidney function was normal. Hemoglobin was in range of 14-15g/dl. To further evaluate the cause of hypoparathyroidism, iron saturation and iron levels were also sent. His iron saturation % was high at 89% with iron level of 286 ug/dl. His ferritin was 224 ng/ml and TIBC was 265 ug/dl. A sample was sent for genetic analysis to rule out hemochromatosis. Homozygous mutations in C282Y gene were found. A diagnosis of hereditary hemochromatosis was made. His other entire hormonal axis was intact. In this case, patient’s hypoparathyroidism is likely an initial manifestation of his HH.Discussion:Hereditary Hemochromatosis (HH) is a genetic disease characterized by an excessive (unregulated) entry of iron into the bloodstream with increased iron deposition in the parenchymal cells of a variety of organs leading to their failure. A defect in the hemochromatosis gene (HFE) is the most common form of HH, also known as the classic form or type 1 HH, where the principal mutation is represented by a substitution of tyrosine for cysteine at position 282 of the HFE gene (C282Y) as seen in our case. According to the genetic forms, the clinical manifestation usually ranges from simple biochemical abnormalities to severe organ damage and disease such as liver cirrhosis, arthritis, DM, cardiomyopathy and hypogonadism.There are reports of hypoparathyroidism from iron overload seen in thalassemia patients and patients who receive long term blood transfusions. In our literature review, this is the first documented case of HH initially manifesting as hypoparathyroidism. As HH is not uncommon in Caucasians, the work up for hemochromatosis as a possible cause of endocrinopathies should be kept in the differential diagnosis. It will help in early diagnosis & treatment which can reverse the effects of the disease leading to better outcomes.

Phenotypic analysis of hemochromatosis subtypes reveals variations in severity of iron overload and clinical disease

AbstractThe clinical progression of HFE-related hereditary hemochromatosis (HH) and its phenotypic variability has been well studied. Less is known about the natural history of non-HFE HH caused by mutations in the HJV, HAMP, or TFR2 genes. The purpose of this study was to compare the phenotypic and clinical presentations of hepcidin-deficient forms of HH. A literature review of all published cases of genetically confirmed HJV, HAMP, and TFR2 HH was performed. Phenotypic and clinical data from a total of 156 patients with non-HFE HH was extracted from 53 publications and compared with data from 984 patients with HFE-p.C282Y homozygous HH from the QIMR Berghofer Hemochromatosis Database. Analyses confirmed that non-HFE forms of HH have an earlier age of onset and a more severe clinical course than HFE HH. HJV and HAMP HH are phenotypically and clinically very similar and have the most severe presentation, with cardiomyopathy and hypogonadism being particularly prevalent findings. TFR2 HH is more intermediate in its age of onset and severity. All clinical outcomes analyzed were more prevalent in the juvenile forms of HH, with the exception of arthritis and arthropathy, which were more commonly seen in HFE HH. This is the first comprehensive analysis comparing the different phenotypic and clinical aspects of the genetic forms of HH, and the results will be valuable for the differential diagnosis and management of these conditions. Importantly, our analyses indicate that factors other than iron overload may be contributing to joint pathology in patients with HFE HH.

Structure-function analysis of ferroportin defines the binding site and an alternative mechanism of action of hepcidin

AbstractNonclassical ferroportin disease (FD) is a form of hereditary hemochromatosis caused by mutations in the iron transporter ferroportin (Fpn), resulting in parenchymal iron overload. Fpn is regulated by the hormone hepcidin, which induces Fpn endocytosis and cellular iron retention. We characterized 11 clinically relevant and 5 nonclinical Fpn mutations using stably transfected, inducible isogenic cell lines. All clinical mutants were functionally resistant to hepcidin as a consequence of either impaired hepcidin binding or impaired hepcidin-dependent ubiquitination despite intact hepcidin binding. Mapping the residues onto 2 computational models of the human Fpn structure indicated that (1) mutations that caused ubiquitination-resistance were positioned at helix-helix interfaces, likely preventing the hepcidin-induced conformational change, (2) hepcidin binding occurred within the central cavity of Fpn, (3) hepcidin interacted with up to 4 helices, and (4) hepcidin binding should occlude Fpn and interfere with iron export independently of endocytosis. We experimentally confirmed hepcidin-mediated occlusion of Fpn in the absence of endocytosis in multiple cellular systems: HEK293 cells expressing an endocytosis-defective Fpn mutant (K8R), Xenopus oocytes expressing wild-type or K8R Fpn, and mature human red blood cells. We conclude that nonclassical FD is caused by Fpn mutations that decrease hepcidin binding or hinder conformational changes required for ubiquitination and endocytosis of Fpn. The newly documented ability of hepcidin and its agonists to occlude iron transport may facilitate the development of broadly effective treatments for hereditary iron overload disorders.

Transferrin Receptors TfR1 and TfR2 Bind Transferrin through Differing Mechanisms.

Hereditary hemochromatosis (HH), a disease marked by chronic iron overload from insufficient expression of the hormone hepcidin, is one of the most common genetic diseases. One form of HH (type III) results from mutations in transferrin receptor-2 (TfR2). TfR2 is postulated to be a part of signaling system that is capable of modulating hepcidin expression. However, the molecular details of TfR2's role in this system remain unclear. TfR2 is predicted to bind the iron carrier transferrin (Tf) when the iron saturation of Tf is high. To better understand the nature of these TfR-Tf interactions, a binding study with the full-length receptors was conducted. In agreement with previous studies with truncated forms of these receptors, holo-Tf binds to the TfR1 homologue significantly stronger than to TfR2. However, the binding constant for Tf-TfR2 is still far above that of physiological holo-Tf levels, inconsistent with the hypothetical model, suggesting that other factors mediate the interaction. One possible factor, apo-Tf, only weakly binds TfR2 at serum pH and thus will not be able to effectively compete with holo-Tf. Tf binding to a TfR2 chimera containing the TfR1 helical domain indicates that the differences in the helical domain account for differences in the on rate of Tf, and nonconserved inter-receptor interactions are necessary for the stabilization of the complex. Conserved residues at one possible site of stabilization, the apical arm junction, are not important for TfR1-Tf binding but are critical for the TfR2-Tf interaction. Our results highlight the differences in Tf interactions with the two TfRs.

Icariin regulates systemic iron metabolism by increasing hepatic hepcidin expression through Stat3 and Smad1/5/8 signaling.

Systemic iron homeostasis is strictly controlled under normal conditions to ensure a balance between the absorption, utilization, storage and recycling of iron. The hepcidin-ferroportin (FPN) axis is of critical importance in the maintenance of iron homeostasis. Hepcidin deficiency gives rise to enhanced dietary iron absorption, as well as to increased iron release from macrophages, and this in turn results in iron accumulation in the plasma and organs, and is associated with a range of tissue pathologies. Low hepcidin levels have been demonstrated in most forms of hereditary hemochromatosis (HH), as well as in β-thalassemia. Therapies that increase hepcidin concentrations may potentially play a role in the treatment of these iron overload-related diseases. To date, natural compounds have not been extensively investigated for this purpose, to the best of our knowledge. Thus, in the present study, we screened natural compounds that have the potential to regulate hepcidin expression. By performing hepcidin promoter-luciferase assay, RT-qPCR and animal experiments, we demonstrated that icariin and berberine were potent stimulators of hepcidin transcription. Mechanistic experiments indicated that icariin and berberine increased hepcidin expression by activating the signal transducer and activator of transcription 3 (Stat3) and Smad1/5/8 signaling pathways. The induction of hepcidin was confirmed in mice following icariin administration, coupled with associated changes in serum and tissue iron concentrations. In support of these findings, the icariin analogues, epimedin A, B and C, also increased hepatic hepcidin expression. However, these changes were not observed in hepcidin-deficient [Hamp1-/- or Hamp1‑knockout (KO)] mice following icariin administration, thereby verifying hepatic hepcidin as the target of icariin. Although berberine exhibited a robust capacity to promote hepcidin expression in vitro, it failed to alter hepcidin expression in mice. Taken together, the findings of the present study suggest that icariin exhibits a robust capacity to increase hepatic hepcidin expression and to modulate systemic iron homeostasis. The present study therefore highlights the significance of using natural compounds to ameliorate iron disorders through the regulation of hepcidin expression.

The global prevalence of HFE and non-HFE hemochromatosis estimated from analysis of next-generation sequencing data

The prevalence of HFE-related hereditary hemochromatosis (HH) among European populations has been well studied. There are no prevalence data for atypical forms of HH caused by mutations in HFE2, HAMP, TFR2, or SLC40A1. The purpose of this study was to estimate the population prevalence of these non-HFE forms of HH. A list of HH pathogenic variants in publically available next-generation sequence (NGS) databases was compiled and allele frequencies were determined. Of 161 variants previously associated with HH, 43 were represented among the NGS data sets; an additional 40 unreported functional variants also were identified. The predicted prevalence of HFE HH and the p.Cys282Tyr mutation closely matched previous estimates from similar populations. Of the non-HFE forms of iron overload, TFR2-, HFE2-, and HAMP-related forms are predicted to be rare, with pathogenic allele frequencies in the range of 0.00007 to 0.0005. Significantly, SLC40A1 variants that have been previously associated with autosomal-dominant ferroportin disease were identified in several populations (pathogenic allele frequency 0.0004), being most prevalent among Africans. We have, for the first time, estimated the population prevalence of non-HFE HH. This methodology could be applied to estimate the population prevalence of a wide variety of genetic disorders.Genet Med 18 6, 618-626.

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.

SLC39A14 Is Required for the Development of Hepatocellular Iron Overload in Murine Models of Hereditary Hemochromatosis

Nearly all forms of hereditary hemochromatosis are characterized by pathological iron accumulation in the liver, pancreas, and heart. These tissues preferentially load iron because they take up non-transferrin-bound iron (NTBI), which appears in the plasma during iron overload. Yet, how tissues take up NTBI is largely unknown. We report that ablation of Slc39a14, the gene coding for solute carrier SLC39A14 (also called ZIP14), in mice markedly reduced the uptake of plasma NTBI by the liver and pancreas. To test the role of SLC39A14 in tissue iron loading, we crossed Slc39a14(-/-) mice with Hfe(-/-) and Hfe2(-/-) mice, animal models of type 1 and type 2 (juvenile) hemochromatosis, respectively. Slc39a14 deficiency in hemochromatotic mice greatly diminished iron loading of the liver and prevented iron deposition in hepatocytes and pancreatic acinar cells. The data suggest that inhibition of SLC39A14 may mitigate hepatic and pancreatic iron loading and associated pathologies in iron overload disorders.

Transferrin Receptor 2 and HFE Regulate Hepcidin Levels Independently of Bmp6 and Hemojuvelin

Hereditary hemochromatosis (HH) is a genetically heterogeneous disorder characterized by elevated iron absorption from the diet, with consequent iron overload and tissue injury. Adult-onset forms of HH are caused by mutations in the HFE gene and in the gene for transferrin receptor 2 (TFR2). Human patients and mouse models of TFR2 and HFE-related HH show inappropriately low expression of hepcidin, the central regulator of iron metabolism. However, although these genes have been discovered far more than a decade ago, the mechanisms by which HFE and TFR2 influence hepcidin expression remain unclear.The bone morphogenetic protein BMP6 plays a key role in the regulation of hepcidin expression. BMP6 binds to type I (ALK3) and type II serine threonine kinase receptors, and to the coreceptor hemojuvelin (HJV), which phosphorylates intracellular SMAD proteins. Phosphorylated SMADs then bind to SMAD4 and translocate to the nucleus to induce the transcription of hepcidin. Inactivation of Bmp6 or Hjv in mice leads to considerably reduced hepcidin production and severe hepatic iron overload. However, there are major differences in hepcidin expression and extrahepatic tissue iron loading between Bmp6 or Hjv KO males and females, due to the suppressive effect of testosterone on hepcidin in males. In contrast to males, Bmp6-/- and Hjv-/-females still produce some hepcidin and do not massively accumulate iron in the pancreas, heart, or kidneys.The goal of this study was to investigate the role of Hfe and Tfr2 in the residual hepcidin production observed in the absence of Bmp6 in females. We used Bmp6-/-, Tfr2-/-, and B2m-/- mice to generate wild-type, single KO (Bmp6-/-, Tfr2-/-, or B2m-/-) and double KO (Tfr2-/- and Bmp6-/-, or B2m-/- and Bmp6-/-) mice, and we assessed Smad5 phosphorylation, hepcidin expression, and the sites of iron accumulation in the different groups of mice. Notably, B2m-/- mice develop spontaneously hepatic iron overload with a distribution similar to that seen in the liver of Hfe-/-mice and the lack of CD8+ lymphocytes and the absence of classical class I molecules in these mice are not responsible for their iron phenotype.Interestingly, the lack of functional Hfe or the lack of Tfr2 in Bmp6-/- females leads to a very similar phenotype that is much more severe than the single impairment of Bmp6, with massive iron loading in extrahepatic tissues, most notably the exocrine pancreas, the heart, and the kidney. Hepcidin mRNA and pSmad levels in the two categories of double KO females were much more strongly downregulated than in single Bmp6-/- females and, in contrast to Bmp6-/-females, no protein was detectable by ELISA in the double KO mice.Our findings clearly demonstrate that Hfe and Tfr2 regulate hepcidin production independently of Bmp6. The symmetrical phenotype of double Bmp6 and Tfr2, or double Bmp6 and Hfe KO mice suggests that Hfe and Tfr2 could participate in the same signaling complex affecting pSmad levels, even if they do not physically interact. Two complexes, one made of ALK3 and HJV, and the other made of ALK2, ALK3, HFE, and TFR2, very likely affect pSMAD levels independently of each other. Signaling through the second complex occurs in the absence of BMP6 and is most probably initiated by another BMP, for instance BMP2 or BMP4 that are also expressed in the liver and, although not regulated by iron, are capable of stimulating hepcidin expression in hepatocytes. Regulation of hepcidin expression by these two complexes would explain why, whereas Alk3, double Bmp6/Hfe, and double Bmp6/Tfr2 deficient females present with iron overload in extrahepatic tissues as do hepcidin KO mice, Bmp6 and Hjv single KO females present with early-onset iron overload only in the liver, similarly to patients with juvenile HH, and mice KO for Alk2, Hfe, or Tfr2 have the least severe phenotype, comparable with that of patients with adult-onset HH. Notably, TFR2 was also shown to localize in lipid rafts where it promotes MAPK activation. Thus, in addition to its role in the complex affecting pSMAD levels, TFR2 could also regulate hepcidin through a parallel pathway involving ERK1/2 signaling. This would explain the more severe phenotype of mice with combined deletion of Hfe and Tfr2 and the fact that, whereas Tfr2-/- mice do not respond to acute iron loading, Hfe-/-mice still have a significant, although blunted hepcidin response.This work was funded in part by FRM (DEQ2000326528) and ANR (ANR-13-BSV3-0015-01). DisclosuresNo relevant conflicts of interest to declare.

The erythroid function of transferrin receptor 2 revealed by Tmprss6 inactivation in different models of transferrin receptor 2 knockout mice

Transferrin receptor 2 (TFR2) is a transmembrane glycoprotein expressed in the liver and in the erythroid compartment, mutated in a form of hereditary hemochromatosis. Hepatic TFR2, together with HFE, activates the transcription of the iron-regulator hepcidin, while erythroid TFR2 is a member of the erythropoietin receptor complex. The TMPRSS6 gene, encoding the liver-expressed serine protease matriptase-2, is the main inhibitor of hepcidin and inactivation of TMPRSS6 leads to iron deficiency with high hepcidin levels. Here we evaluate the phenotype resulting from the genetic loss of Tmprss6 in Tfr2 total (Tfr2(-/-)) and liver-specific (Tfr2(LCKO)) knockout mice. Tmprss6(-/-)Tfr2(-/-) and Tmprss6(-/-)Tfr2(LCKO) mice have increased hepcidin levels and show iron-deficiency anemia like Tmprss6(-/-)mice. However, while Tmprss6(-/-)Tfr2(LCKO) are phenotypically identical to Tmprss6(-/-) mice, Tmprss6(-/-)Tfr2(-/-) mice have increased red blood cell count and more severe microcytosis than Tmprss6(-/-) mice. In addition hepcidin expression in Tmprss6(-/-)Tfr2(-/-) mice is higher than in the wild-type animals, but lower than in Tmprss6(-/-) mice, suggesting partial inhibition of the hepcidin activating pathway. Our results prove that hepatic TFR2 acts upstream of TMPRSS6. In addition Tfr2 deletion causes a relative erythrocytosis in iron-deficient mice, which likely attenuates the effect of over-expression of hepcidin in Tmprss6(-/-) mice. Since liver-specific deletion of Tfr2 in Tmprss6(-/-) mice does not modify the erythrocyte count, we speculate that loss of Tfr2 in the erythroid compartment accounts for the hematologic phenotype of Tmprss6(-/-)Tfr2(-/-) mice. We propose that TFR2 is a limiting factor for erythropoiesis, particularly in conditions of iron restriction.

A Late Presentation of a Fatal Disease: Juvenile Hemochromatosis

Juvenile hemochromatosis is a rare and severe form of hereditary hemochromatosis. We report the case of a 39-year-old female who presented with heart failure and cirrhosis from previously unrecognized juvenile hemochromatosis. This is the latest presentation described in the literature. An important clue to the diagnosis was a history of amenorrhea since the age of 20 that had never been investigated. The patient died of intractable heart failure two months after the initial presentation. Juvenile hemochromatosis should be suspected in a young patient with endocrine or cardiac manifestations. Early diagnosis is crucial since phlebotomy can improve the prognosis and delay or prevent progression to heart failure and cirrhosis.

A Novel Rat Model of Hereditary Hemochromatosis Due to a Mutation in Transferrin Receptor 2

AbstractAbstract 612Sporadic iron overload has been reported previously in rats but the underlying cause has not been ascertained. In this study, phenotypic analysis of a subpopulation of Wistar rats designated Hsd:HHCL revealed a low incidence of histologically detected liver iron overload. One rat out of 132 screened animals exhibited liver iron accumulation in a predominantly periportal, hepatocellular distribution; this male rat expressed low RNA levels of the iron regulatory hormone hepcidin and low protein levels of transferrin receptor 2, a membrane protein essential for hepcidin expression in humans and mice and mutated in forms of hereditary hemochromatosis, a disease of excessive intestinal iron absorption and progressive tissue iron overload. Sequencing of the transferrin receptor 2 gene in the iron-overloaded rat revealed a novel Ala679Gly polymorphism affecting a highly conserved residue. Quantitative trait locus mapping revealed that a transferrin receptor 2 polymorphism correlated strongly with serum iron and transferrin saturations in male rats. Transfection of Tfr2 expression constructs into tissue culture cell lines revealed that the Gly679 Tfr2 variant is expressed at a lower level than the Ala679 variant. Selective breeding of rats carrying this polymorphism and characterization of iron metabolism in the resulting progeny indicated that homozygosity for the Ala679Gly allele leads to a hemochromatosis phenotype. The Hsd:HHCL rat is the first genetic rat model of hereditary hemochromatosis and may prove useful for understanding the molecular mechanisms underlying the regulation of iron metabolism and the pathogenesis of hereditary hemochromatosis. Disclosures:No relevant conflicts of interest to declare.

Minihepcidins prevent iron overload in a hepcidin-deficient mouse model of severe hemochromatosis

AbstractThe deficiency of hepcidin, the hormone that controls iron absorption and its tissue distribution, is the cause of iron overload in nearly all forms of hereditary hemochromatosis and in untransfused iron-loading anemias. In a recent study, we reported the development of minihepcidins, small drug-like hepcidin agonists. Here we explore the feasibility of using minihepcidins for the prevention and treatment of iron overload in hepcidin-deficient mice. An optimized minihepcidin (PR65) was developed that had superior potency and duration of action compared with natural hepcidin or other minihepcidins, and favorable cost of synthesis. PR65 was administered by subcutaneous injection daily for 2 weeks to iron-depleted or iron-loaded hepcidin knockout mice. PR65 administration to iron-depleted mice prevented liver iron loading, decreased heart iron levels, and caused the expected iron retention in the spleen and duodenum. At high doses, PR65 treatment also caused anemia because of profound iron restriction. PR65 administration to hepcidin knockout mice with pre-existing iron overload had a more moderate effect and caused partial redistribution of iron from the liver to the spleen. Our study demonstrates that minihepcidins could be beneficial in iron overload disorders either used alone for prevention or possibly as adjunctive therapy with phlebotomy or chelation.

Hereditary hemochromatosis of tongue

Hereditary hemochromatosis (HH) refers to several inherited disorders of iron metabolism leading to tissue iron overload. Classical HH is associated with mutations in HFE (C282Y homozygotes or C282Y/H63D compound heterozygotes) and is almost exclusively found in populations of northern European descent. Non-HFE-associated HH is caused by mutations in other recently identified genes involved in iron metabolism. Hepcidin is an iron regulatory hormone that inhibits ferroportin-mediated iron export from enterocytes and macrophages. Defective hepcidin gene expression or function may underlie most forms of HH. Target organs and tissues affected by HH include the liver, heart, pancreas, joints, and skin, with cirrhosis and diabetes mellitus representing late signs of disease in patients with markedly elevated liver iron concentration. Recently, we have encountered the rare representation of this disease of the oral cavity associated with generalized burning sensation of the tongue. The diagnosis was established accidently, from the lab investigations, otherwise the patient was healthy and free from classical signs and symptoms of the disease. The patient was adequately treated by phlebotomy. To conclude, all patients with a chief complaint of burning sensation of the oral cavity and tongue should be adequately screened for hereditary hemochromatosis to prevent the associated mortality and morbidity with the hemochromatosis.

Visão atual da hemocromatose hereditária

A hemocromatose hereditária (HH) está relacionada a diversos distúrbios do metabolismo do ferro que ocasionam sua sobrecarga tecidual. A HH clássica está associada às mutações do gene HFE (homozigose para C282Y ou duplo heterozigose para C282Y/H63D), sendo encontrada quase exclusivamente em descendentes do norte Europeu. A hemocromatose hereditária, quando não relacionada ao gene HFE, é causada por mutações de outros genes, recentemente identificados, envolvidos no metabolismo do ferro. Hepcedina é o hormônio regulador do ferro que inibe a ferroportina, proteína exportadora de ferro dos enterócitos e dos macrófagos; um defeito na expressão do gene da hepcedina ou na sua função costuma ser a causa da maioria dos tipos de hemocromatose hereditária. Os alvos acometidos pela HH são órgãos e tecidos - fígado, coração, pâncreas, articulações e pele -, sendo a cirrose e o diabetes melito os sinais tardios da doença em pacientes com expressivo aumento da concentração hepática de ferro. Pacientes com diagnóstico estabelecido de hemocromatose hereditária e sobrecarga de ferro devem ser tratados com flebotomia para a obtenção de depleção do ferro do organismo; em seguida, com flebotomia de manutenção. As causas mais frequentes de morte por hemocromatose hereditária são câncer hepático, cirrose, miocardiopatia e diabete; entretanto, pacientes submetidos à depleção do ferro de maneira satisfatória e antes do desenvolvimento da cirrose ou da diabete podem ter sobrevida normal.

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.

Homozygous form of hereditary hemochromatosis in a patient with beta-thalassemia minor: case report

Background: Diagnostic approach to the simultaneous inheritance of beta-thalassemia and hereditary hemochromatosis might be quite complex due to the fact that severe beta-thalassemia itself may lead to hemochromatosis. On the other hand, beta-thalassemia minor accompanied by some heterozygous form of HFE polymorphism may also lead to the disease manifestation. These conditions as well as the homozygous forms of HFE polymorphisms are hemochromatosis risk factors that may lead to liver cirrhosis and hepatocellular carcinoma. Therefore, early diagnosis is crucial for patient quality of life and life expectancy. Methods: A febrile patient admitted to Department of Infectious Diseases, Osijek University Hospital, with hepatosplenomegaly and some neurological symptoms has been chosen for this case report. Basic laboratory tests as well as ultrasound examination of the abdomen and magnetic resonance imaging of the head were performed shortly upon admission. Liver biopsy, hemoglobin electrophoresis, haptoglobin concentration and Cys282Tyr polymorphism determination were subsequently obtained. Results: History data and laboratory findings suggested the diagnosis of beta-thalassemia. Extended laboratory work-up pointed to the diagnosis of pigment cirrhosis-hemochromatosis, and verified the diagnosis of beta-thalassemia minor. Appropriate molecular diagnostic procedure indicated the homozygous form of hereditary hemochromatosis. Conclusions: In this case of homozygous hereditary hemochromatosis and beta-thalassemia minor coinheritance, serum ferritin concentration, tran-sferrin saturation, hemoglobin electrophoresis and HFE gene Cys282Tyr polymorphism analysis proved to be crucial for the relatively fast establishment of accurate diagnosis. Recognition of the homozygous form of hemochromatosis in association with beta-thalassemia minor explained the complexity and severity of the disease presentation.