Hemochromatosis: Hereditary hemochromatosis and HFE gene.

Hereditary Hemochromatosis (HH) is an autosomal recessive genetic disease, characterized by an excessively increased absorption of dietary iron. Excess iron can be accumulated because of the lack of an effective excretory mechanism leading to toxic effects. HH is one of the most common genetic disorders in individuals of European descent. Genetic polymorphisms of the HFE gene (rs1800562, rs1799945 and rs1800730) also affect the normal activity of another protein, hepcidin, a negative regulator of iron homeostasis. If left untreated, hereditary hemochromatosis can lead to morbidity and eventually death. Clinical onset hereditary hemochromatosis symptoms occur more frequently in adult men than women, as the monthly loss of iron due to menstruation in women slows down accumulation and the symptoms usually start appearing after menopause. Therapeutic phlebotomy is the primary form of treatment for this disease so far, combined with the use of chelating agents. Orthotopic liver transplantation (OTL) is performed in patients with advanced cirrhosis. In order to prevent the progression of iron accumulation, an early detection may be achieved by genotypic check of the frequent mutations of the HFE. Consequently, initiation of treatment may take place before the development of clinical symptoms, particularly cirrhosis, contributing significantly in achieving normal life expectancy. Therefore, genotypic check is vital in order to prevent the development of this type of hemochromatosis.

Identification of Genes for Hereditary Hemochromatosis.

Hereditary hemochromatosis (HH) is one of the most common genetically transmitted conditions in individuals of Northern European ancestry. The disease is characterized by excessive intestinal absorption of dietary iron, resulting in pathologically high iron storage in tissues and organs. If left untreated, HH can damage joints and organs, and eventually lead to death. There are four main classes of HH, as well as five individual molecular subtypes, caused by mutations in five genes, and the approaches implemented in the discovery of each HH type have specific histories and unique aspects. In this chapter, we review the genetics of the different HH types, including the strategies used to detect the causal variants in each case and the manner in which genetic variants were found to affect iron metabolism.

Hemocromatosis: a changing world.

Due to major advances in the understanding of iron metabolism as well as in the bioche- iuical, imaging, and genetic domains: i) The nosologicalframework of hemochromatosis (HC) encompasses not only HFE-HC, by far the most frequent HC form, but also non-HFE HC diseases which comprise essentially juvenile HC and the ferroportin disease. ii) The diagnostic approach has become totally non invasive, based on clinical, imaging and biological data. iii) The treatment remains, for most forms, based on venesections, but the innovative emerging therapeutic approach is represented by hepcidin supplementation.

[Chronic liver diseases--new therapy. Are biopsies necessary?]. / Chronische Lebererkrankungen--neue Therapie. Benötigen wir die Biopsie?

Chronic liver disease can often reliably be assessed only by examination of biopsy material. In this article the possible indications for liver biopsy in viral hepatitis B and C, autoimmune liver disease, steatohepatitis and hereditary metabolic diseases are described. A biopsy may be useful in cases with unclear clinical or serological situations or with questionable chronicity and comorbidities. The assessment of biopsy material should be based on guideline-based classification systems. The value of biopsy diagnosis benefits from a close interdisciplinary clinical pathological cooperation.

Hereditary hemochromatosis.

Hereditary hemochromatosis is an autosomal recessive disorder that disrupts the body's regulation of iron. It is the most common genetic disease in whites. Men have a 24-fold increased rate of iron-overload disease compared with women. Persons who are homozygous for the HFE gene mutation C282Y comprise 85 to 90 percent of phenotypically affected persons. End-organ damage or clinical manifestations of hereditary hemochromatosis occur in approximately 10 percent of persons homozygous for C282Y. Symptoms of hereditary hemochromatosis are nonspecific and typically absent in the early stages. If present, symptoms may include weakness, lethargy, arthralgias, and impotence. Later manifestations include arthralgias, osteoporosis, cirrhosis, hepatocellular cancer, cardiomyopathy, dysrhythmia, diabetes mellitus, and hypogonadism. Diagnosis requires confirmation of increased serum ferritin levels and transferrin saturation, with or without symptoms. Subtyping is based on genotypic expression. Serum ferritin measurement is the most useful prognostic indicator of disease severity. Liver biopsy is performed to stage the degree of fibrosis with severe ferritin elevation or transaminitis, or to diagnose nonclassical hereditary hemochromatosis in patients with other genetic defects. Treatment of hereditary hemochromatosis requires phlebotomy, and the frequency is guided by serial measurements of serum ferritin levels and transferrin saturation. Iron avidity can result from overtreatment. If iron avidity is not suspected, it may mimic undertreatment with persistently elevated transferrin saturation. Dietary modification is generally unnecessary. Universal screening for hereditary hemochromatosis is not recommended, but testing should be performed in first-degree relatives of patients with classical HFE-related hemochromatosis, those with evidence of active liver disease, and patients with abnormal iron study results. Screening for hepatocellular carcinoma is reserved for those with hereditary hemochromatosis and cirrhosis.

Sobrecarga de hierro y enfermedad hepática: aspectos clínicos y terapéuticos / Iron overload and liver disease: clinical and therapeutic issues

Iron accumulation in parenchymal cells results in toxic damage and cell death which can determine a functional organ failure. The prototypical disease is hereditary hemochromatosis (HH). HH has been associated to mutations affecting any of the proteins that regulate iron metabolism. The most common cause of HH is a mutation in the HFE gene [C282Y]. Mutations in the gene for the hormone hepcidin and any of other eight genes that regulate iron biology, including the transferrin receptor 2 (TfR2), hemojuvelin (HJV) and ferroportin (FPN), also cause iron overload and hemochromatosis. Although information is limited, HFE-associated to HH is uncommon in Chile. Evaluation of iron overload in clinical practice should include consideration of co-factors such as alcohol consumption, the presence of virus infection hepatitis C virus and nonalcoholic steatohepatitis, which independently can contribute to iron accumulation. While genetic testing is useful, analysis of liver histology and imaging evaluation of iron overload by MRI are important tools for clinical evaluation. This article reviews current concepts on the clinical diagnosis and management of hepatic iron overload.

La acumulación de hierro en las células parenquimatosas determina la ocurrencia de daño tóxico y muerte celular, lo que puede producir una insuficiencia funcional. La enfermedad prototípica es la hemocromatosis hereditaria (HH). La HH se ha asociado a mutaciones que afectan a cualquiera de las proteínas que regulan el metabolismo del hierro. La causa más común de HH es una mutación en el gen HFE [C282Y]. Mutaciones en el gen de la hormona hepcidina (HAMP) y cualquiera de los 8 genes que regulan su biología, incluyendo el receptor de transferrina 2 (TfR2), hemojuvelina (HJV) y ferroportina(FPN), también causan sobrecarga de hierro y hemocromatosis. Aunque la información es limitada, la HH asociada a HFE es infrecuente en nuestro medio. La evaluación de la sobrecarga de hierro en la práctica clínica debe contemplar la evaluación de otros factores tales como el consumo de alcohol, la presencia de infección por el virus de la hepatitis por virus C y de esteatohepatitis no alcohólica. Si bien el test genético es de utilidad, los análisis de la histología hepática y la evaluación imagenológica de la sobrecarga de hierro mediante resonancia magnética son útiles para la evaluación clínica de la sobrecarga de hierro. El presente artículo revisa conceptos actuales sobre el manejo clínico de la sobrecarga de hierro hepática.

[Diagnosis of iron overload syndrome].

The article presents a classification of conditions, accompanied with increasing of iron accumulation of the liver cells, normal iron metabolism in the human body, etiology, epidemiology, multifactorial structure of the pathogenesis of HFE homozygous hemochromatosis, clinic of iron overload syndrome. The modern algorithms of diagnostic and tactics of patients with the use of genotyping and correction of iron content.

[Hereditary iron overload]. / Surcharges héréditaires en fer.

The field of hereditary iron overload has known, in the recent period, deep changes mainly related to major advances in molecular biology. It encompasses now a series of genetic entities. The mechanistic understanding of iron overload development and iron toxicity has greatly improved. The diagnostic approach has become essentially noninvasive with a major role for biological tests. From the therapeutic viewpoint, the phlebotomy treatment is now enriched by the possibility of resorting to oral chelation and by innovative perspectives directly linked to our improvement in the molecular understanding of these diseases.

[Hereditary hemochromatosis]. / Die hereditäre Hämochromatose.

Genetic hemochromatosis is classified into four subtypes of which only type 1 is of clinical importance in Caucasians. Type 1 is due to an autosomal recessive inborn error of metabolism; the homozygous C282Y mutation of the HFE gene on chromosome 6 accounts for more than 90% of the clinical phenotype in populations of Celtic origin. The mutation leads to an inadequately high intestinal iron absorption which may finally cause iron overload in and damage to various organs. Type 2 is the juvenile form of iron overload which leads to a severe phenotype prior to age 30 with cardiomyopathy and hypogonadism. The corresponding mutations are located in the hemojuveline and hepcidin genes. Typ 3 has mainly been described in Italian families and refers to mutations in transferrin receptor 2 gene. Histopathologic and clinical consequences of type 3 hemochromatosis are similar to those seen in type 1. Types 2 and 3 are autosomal recessive traits. Type 4 hemochromatosis follows an autosomal dominant trait; the corresponding mutation affects the basolateral iron carrier ferroportin 1. Diagnosis of hemochromatosis is based on determinations of serum ferritin and transferrin saturation with the latter being more sensitive and specific. In case of a homozygous C282Y gene test, liver biopsy is not required for diagnosis. Liver biopsy is, however, recommended in C282Y homozygotes at ferritin values > 1,000 ng/ml because of an increased risk for liver fibrosis. Phlebotomy treatment is the standard care to remove iron in genetic hemochromatosis. Patients treated in the early noncirrhotic stage have a normal life expectancy. Thus, future efforts should aim at early diagnosis. Iron removal also improves the outcome in cirrhotic patients. Liver carcinoma may develop in cirrhotic patients despite iron depletion. Liver cancers without cirrhosis are so rare that screening is only recommended in cirrhotic patients.

Rare types of genetic hemochromatosis.

Most types of genetic hemochromatosis are due to mutations in the HFE gene, although similar iron overload and organ damage can also result from mutations in genes other than HFE in rare types of hemochromatosis. Non-HFE hemochromatoses have been divided into two subgroups with distinctive features. The first includes juvenile and TFR2-related hemochromatoses that, similar to HFE hemochromatosis, show recessive inheritance, increased transferrin saturation, iron storage in hepatocytes and responsiveness to phlebotomy. Disorders in this subgroup, although differing regarding the severity of iron overload and/or the age at presentation, are all either due to hepcidin deficiency or to the inability to increase hepcidin levels according to iron stores. The second subgroup of hemochromatosis is caused by autosomal dominant mutations in the SLC40A1 gene encoding the iron exporter ferroportin with distinctive features. Iron loading of Kupffer cells and normal transferrin saturation characterize the so-called 'ferroportin disease'. In contrast, few mutations in SLC40A1 that cause hepcidin resistance lead to a hemochromatosis-like phenotype with dominant inheritance. The precise diagnosis of the genetic type of hemochromatosis is relevant for the follow-up, treatment, and for family counseling.

[Genetic iron overloads and hepatic insulin-resistance iron overload syndrome: an update]. / Surcharges en fer d'origine génétique et hépatosidérose dysmétabolique.

Hepcidin inhibits intestinal absorption of iron through internalisation of ferroportin. Its discovery helps to better understand the genetic iron overloads. The insulin resistance-hepatic iron overload (IR-HIO)--also coined as the dysmetabolic iron overload syndrome--is a common cause or iron overload. This article is a review about genetic iron overloads and IR-HIO. Type 1 haemochromatosis C282Y +/+ accounts for 95% of the haemochromatosis. Hepatic fibrosis may develop if serum ferritin is higher than 1000 microg/l but can be partially reversible with phlebotomies. Juvenile haemochromatosis (type 2) and type 3 haemochromatosis (mutation of the transferrin receptor 2) are very uncommon. Several mutations of the ferroportin gene can cause usually mild iron overload of autosomal dominant inheritance. Aceruleoplasminemia is an uncommon disorder involving cerebral iron overload. The causes and consequences of the IR-HIO are unknown. Treatment of IR-HIO is focused on metabolic syndrome and phlebotomies are questionable because the overload is moderate and intestinal absorption of iron seems to be low. MRI (or other non invasive methods) is needed to truly assess iron overload because serum ferritin overestimates it in metabolic syndrome. Several points have to be elucidated: how HFE interferes with hepcidin in type 1 haemochromatosis; the causes of variability of iron overload; the benefits of populations screening; the advantage of phlebotomies in IR-HIO; the use of new oral iron chelators.

[Novel aspects of pathogenesis of hereditary hemochromatosis]. / Nowe aspekty patogenetyczne wrodzonej hemochromatozy.

Patients with hereditary hemochromatosis (HC) may present a plenty of clinical symptoms, thus are referred to various specialists and may prone a significant diagnostic dillema. The molecular basis of hemochromatosis is more complex than expected. In 1996 HFE gene was identified and its main mutations (C282Y and H63D) were described as well as their high frequency in population of European descent. Them: Most patients with clinical symptoms of hemochromatosis are homozygous for C282Y but it is also clear that some families are linked to rarer conditions, named "non-HFE hemochromatosis". Between 2000-2004 other genes involved in iron homeostasis were intensively studied, leading to recognition of hepcidin (HAMP) - the most important iron hormone, hemojuvelin (HJV), transferin receptor 2 (TfR2) and ferroportin. Recent findings led to novel hypothesis on potential digenic modes of inheritance or the involvement of modifier genes. Hepcidin plays a central role in mobilization of iron, HFE, TfR2 and HJV playing a modulating role in its production, related to the body's iron status. It has also been demonstrated that HAMP negatively regulates cellular iron efflux by affecting the ferroportin cell surface availability. The result of such a wide investigations is OMIM classification of hereditaty hemochromatosis, typing four types of the disease.

A novel mutation of transferrin receptor 2 in a Taiwanese woman with type 3 hemochromatosis.

Hereditary hemochromatosis (HH) is very rare in Asia. Here, we describe a Taiwanese woman presenting with fully developed characteristics of HH including bronze skin, DM, decreased MRI T2 signal intensity over liver and pituitary gland. Biochemistry of iron profile indicated a severe status of iron overload by serum iron: 194 microg/dL, serum ferritin: 6640 microg/L, transferrin saturation: 92.8%. By measuring the hepatic iron index 8.48 (>1.9) of her liver biopsy tissue, the diagnosis of HH was established. Diagnosis of non-HFE HH was carried out since the whole HFE genome was sequenced but failed to localize any genetic alterations. The whole genome of transferrin receptor 2 (TfR2) was sequenced and a novel mutation of 13528 G-->A (Arg 481 His) in exon 11 was detected. Therefore, type 3 hemochromatosis was confirmed. The distinct clinical features, extremely high iron index and impressive iron staining in her liver biopsy tissue may represent an aggravated iron deposition in the liver caused by this novel mutation. Our finding implicates functional importance of histidine in exchange of arginine at amino acid 481 of transferrin receptor 2 in iron homeostasis. This case reminds physicians in Asia to keep in mind that hemochromatosis could be a rare cause of DM.

Hiperpigmentación cutánea y homeostasis del hierro: rol de la hepcidina / Cutaneous hyperpigmentation and homeostasis of iron: role of the hepcidin

La hiperpigmentación cutánea por melanina en zonas expuestas al sol puede estar asociada a un desequilibrio en la homeostasis del hierro. La hepcidina es un péptido responsable de la regulación negativa de la absorción del hierro en el intestino delgado y de su liberación por los macrófagos. Posee capacidad antimicrobiana. Es sintetizada en el hígado, secretada al torrente circulatorio y excretada por la orina. La sobreexpresión causa anemia y su déficit, sobrecarga de hierro (acumulación en diferentes órganos y hemocromatosis hereditaria). Los antagonistas de la hepcidina podrían utilizarse en el tratamiento de la anemia resistente a eritropoyetina, asociada a procesos crónicos. Por su parte, los agonistas o sustancias que estimulen la producción de hepcidina, podrían constituir un tratamiento en enfermedades con sobrecarga de hierro (siderosis) y por consiguiente, corregir la hiperpigmentación asociada.

The cutaneous hyperpigmentation by melanin in zones of the skin exposed to the sun can be associated to an imbalance in the homeostasis of the iron. The hepcidin is a peptide responsible for the negative regulation of the absorption of the iron in the small intestine and of its liberation by the macrophages. It has, in addition, antimicrobial capacity. It is synthesized in the liver, secreted to the circulatory torrent and excreted by the urine. Its overexpression causes anemia and its deficit iron overload (accumulation in different organs and hereditary hemochromatosis), The antagonists of the hepcidin, could be used in the treatment of anemia resistant to erythropoyetin associated to chronic processes. On the other hand, the agonists or substances that stimulate the hepcidin production, could constitute a treatment in diseases with overload of iron (siderosis) and therefore, to correct the associate.hyperpigmentation.

Molecular and clinical aspects of iron homeostasis: From anemia to hemochromatosis.

The discovery in recent years of a plethora of new genes whose products are implicated in iron homeostasis has led to rapid expansion of our knowledge in the field of iron metabolism and its underlying complex regulation in both health and disease. Abnormalities of iron metabolism are among the most common disorders encountered in practical medicine and may have significant negative impact on physical condition and life expectancy. Basic insights into the principles of iron homeostasis and the pathophysiological and clinical consequences of iron overload, iron deficiency and misdistribution are thus of crucial importance in modern medicine. This review summarizes our current understanding of human iron metabolism and focuses on the clinically relevant features of hereditary and secondary hemochromatosis, iron deficiency anemia, anemia of chronic disease and anemia of critical illness. The interconnections between iron metabolism and immunity are also addressed, in as much as they may affect the risk and course of infections and malignancies.

Hereditary hemochromatosis: genetic complexity and new diagnostic approaches.

Since the discovery of the hemochromatosis gene (HFE) in 1996, several novel gene defects have been detected, explaining the mechanism and diversity of iron-overload diseases. At least 4 main types of hereditary hemochromatosis (HH) have been identified. Surprisingly, genes involved in HH encode for proteins that all affect pathways centered around liver hepcidin synthesis and its interaction with ferroportin, an iron exporter in enterocytes and macrophages. Hepcidin concentrations in urine negatively correlate with the severity of HH. Cytokine-mediated increases in hepcidin appear to be an important causative factor in anemia of inflammation, which is characterized by sequestration of iron in the macrophage system. For clinicians, the challenge is now to diagnose HH before irreversible damage develops and, at the same time, to distinguish progressive iron overload from increasingly common diseases with only moderately increased body iron stores, such as the metabolic syndrome. Understanding the molecular regulation of iron homeostasis may be helpful in designing innovative and reliable DNA and protein tests for diagnosis. Subsequently, evidence-based diagnostic strategies must be developed, using both conventional and innovative laboratory tests, to differentiate between the various causes of distortions of iron metabolism. This review describes new insights in mechanisms of iron overload, which are needed to understand new developments in diagnostic medicine.

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.