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Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetic haemochromatosis (GH) is one of the most common hereditary diseases, with a prevalence of 1-5/1000 in the Western world. In 90 per cent of cases a mutation is found in an MHC-class-like gene designated HFE, involving a substitution at position 282 of the HFE protein and resulting in defective binding of beta(2)-microglobulin. Animals with beta(2)-microglobulin deficiency develop iron overload, indicating this protein to be involved in the regulation of iron metabolism. Hepatic iron overload results in increased production of oxygen free radicals and peroxidation of membrane lipids, thus causing damage to lysosomes, mitochondria and the endoplasmic reticulum. These cellular events may progress to cell death, fibrogenesis, and the development of liver cirrhosis which is associated with a 200-fold increase in risk of hepatocellular carcinoma. In addition to the risk of diabetes, arthralgia, cardiac arrhythmia, pituitary insufficiency and hypogonadism, iron excess is also associated with aggravation of the cytotoxic effects exerted on hepatocytes by other agents such as alcohol or hepatotrophic viruses. The treatment of iron overload in GH consists of weekly venesection until the serum ferritin level is normalized, followed by maintenance therapy. Survival rates are normal if the disease is detected and treated before complications have developed.
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PMID:[Defective iron metabolism in genetic hemochromatosis. The mechanisms remain unknown in spite of genetic advances]. 972 62

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder that can result in iron overload and a wide range of clinical complications, including hepatic cirrhosis, diabetes mellitus, hypopituitarism, hypogonadism, arthritis, and cardiomyopathy. People with HH can be detected at an asymptomatic stage of the disease by abnormalities in serum iron measures. Early detection is desirable, because periodic phlebotomy provides effective treatment for iron overload and may prevent complications of the disorder. The natural history of HH is poorly understood, however, and the proportion of people detected by screening who will develop serious complications of HH is unknown. The genetics of HH may help to resolve these questions. The gene, HFE, and two mutations, C282Y and H63D, have been identified: the C282Y mutation has a higher penetrance than the H63D mutation, and appears to result in a greater loss of HFE protein function. Most people with HH are C282Y homozygotes, a small proportion are compound heterozygotes or H63D homozygotes, and some have no identifiable HFE mutation or are HFE heterozygotes, suggesting that additional mutations associated with HH are yet to be found. Gender and environmental agents, such as alcohol and dietary iron, influence phenotypic expression of HH. The severity of HH is thus determined by an interaction between genotype and modifying factors. HFE mutations also appear to increase the likelihood of iron overload in inherited anemias and to promote the clinical manifestations of porphyria cutanea tarda. HH is an important paradigm for medical genetics because it offers an opportunity to explore the complexity of gene gene and gene environment interactions.
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PMID:Hemochromatosis: genetics helps to define a multifactorial disease. 972 31

Hemochromatosis is a recessive disorder of iron metabolism characterized by progressive iron loading of parenchymal organs, which accounts for clinical complications such as cirrhosis, diabetes mellitus, cardiopathy, endocrine dysfunctions and arthropathy. Clinical complications, which usually develop after the third or fourth decade of life, can be fatal but may be prevented by phlebotomy if iron excess is detected at a very early stage. The hemochromatosis gene (HFE), located 4.5 megabases telomeric to the HLA-A locus, encodes an HLA class I like protein and two missense mutations, C282Y and H63D in complete disequilibrium have been identified within this gene. Due to its high frequency in the general population, the involvement of H63D in the pathogenesis of the disease remains controversial, and it might correspond to a minor mutation. Conversely, the C282Y mutation is tightly linked to the disease, as it accounts for 80 to 100% of the hemochromatosis cases in Northern Europe. The lower frequency observed, in the patients, in Italy and South of France led to imagine either the implication of other mutations or of other genes. The C282Y mutation is absent in Asia and Africa and is present in the general population with a decreasing gradient of frequency from Northern to Southern Europe. The prevalence of the disease was usually estimated to be 3% but the observed frequency of the C282Y homozygotes is 5% in our breton population raising the question of the penetrance of the disease, and consequently the use of the genotypic test for its systematic screening. As HFE encodes a membrane protein similar to HLA class I protein, its contribution to iron overload is not obvious. The normal protein is predicted to to be expressed at the cell surface in association with beta 2-microglobulin, a localization for which C282Y is critical as it disrupts this association. This protein has also been shown to form a stable complex with the transferrin receptor leading to a decreased affinity for transferrin. A better knowledge of its function will help to decipher iron and different metal-ions metabolism. Although the exact role of the HFE protein is unknown, the genotypic test allows the clinicians to ascertain their diagnosis and genetic counselling.
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PMID:[Molecular genetics of hemochromatosis]. 1052 Apr 11

Like most essential nutrients, Fe needs to be maintained in the body at a defined level for optimal health, with appropriate adaptation to varying Fe needs and supply. The primary mechanism for controlling Fe level is the regulation of Fe absorption. Several different proteins have been identified as contributors to the process. Despite a complex regulatory system, Fe disorders (both Fe deficiency and Fe overload) occur. Fe deficiency is a common problem worldwide, resulting from inadequate dietary Fe and blood loss. Complications include pre-term labour, developmental delay, and impaired work efficiency. No specific genetic syndromes causing isolated Fe deficiency have been described, but animal studies and clinical observations suggest that such a relationship may be a possibility. Conversely, the known causes of Fe overload are genetic. Fe overload is less common than Fe deficiency, but can result in serious medical complications, including cirrhosis, primary liver cancer, diabetes, cardiomyopathy and arthritis. The most common and best characterized syndrome of Fe overload is hereditary haemochromatosis (HHC), an autosomal recessive disorder. Mutations in the HFE protein cause HHC, but the clinical presentation is variable. Of particular interest is the factor that some FIFE genotypes appear to be associated with protection from Fe deficiency. Other genetic variants in the regulatory pathway may influence the likelihood of Fe deficiency and Fe overload. Studies of genetic variants in HFE and other regulatory proteins provide important tools for studying the biological processes in Fe regulation. This work is likely to lead to new insights into Fe disorders and potentially to new therapeutic approaches. It will not be complete, however, until coordinated study of both genetic and nutritional factors is undertaken.
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PMID:Iron deficiency and iron overload: effects of diet and genes. 1131 Apr 26

Hereditary hemochromatosis (hh, type 1 hemochromatosis) is an autosomal recessive trait characterized by hyperabsorption of dietary iron. The disease trait occurs in approximately five per thousand Caucasians of northern European descent. The causative gene, designated HFE, was isolated and characterized in 1996; most individuals with hh are homozygous for a mutation resulting in a change from cysteine to tyrosine at residue 282 of the HFE protein (C282Y). Wild-type HFE protein binds to the transferrin receptor, and by an undefined mechanism the enterocyte is "programmed" to absorb an amount of dietary iron precisely matched to the body's needs. The C282Y mutant protein is not expressed on the cell surface and does not bind to the transferrin receptor; the result is an enterocyte programmed to absorb slightly more iron than required. Most individuals with hh display a common laboratory phenotype, an elevated transferrin saturation. Iron stores in excess of normal eventually occur in most men and some women. The prevalence of organ damage due to iron overload, however, remains a controversial issue. Published estimates range from less than 1% to "nearly all." The main reason for this discrepancy has been ascertainment bias. Retrospective studies have been biased in favor of individuals with morbid complications of hh, whereas screening studies of groups such as blood donors generally include only healthy subjects. We focus here on a review of studies that have attempted to avoid ascertainment bias. If biopsy-proven hepatic fibrosis and/or cirrhosis is employed as the single criterion for disease-related morbidity, clinical penetrance of hh occurs in 4% to 25% of homozygotes. This range, although narrower than in biased studies, is still wide and requires clarification. A large-scale population-based study has been sponsored by the National Institutes of Health to address this issue. Until results become available, the pragmatic approach is to continue to screen for hemochromatosis in the primary care setting and to maintain serum ferritin values at approximately 100 micro g/L or lower with phlebotomy therapy.
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PMID:Hereditary hemochromatosis. 1238 98

Haemochromatosis is most commonly due to the autosomal recessive inheritance of a C282Y substitution in the HFE protein, whereby both alleles of the corresponding gene are affected. The disease is characterised by an inappropriate increase in intestinal iron absorption due to reduced expression of the iron regulatory protein, hepcidin. Progressive iron deposition in parenchymal tissues may ultimately lead to liver and other organ toxicity. The characteristic biochemical abnormalities are raised serum ferritin and transferrin saturation, which can be used in conjunction with genetic tests and emerging magnetic resonance imaging-based techniques to diagnose patients with the disorder. Progressive iron overload can manifest clinically as advanced fibrosis, cirrhosis and hepatocellular carcinoma. Enigmatically, the penetrance of both raised iron indices and clinically significant disease is incomplete in patients with hereditary haemochromatosis. Regardless, advanced clinical presentations of the disease have become less common due to increased awareness and earlier diagnosis. On the other hand, obesity and alcohol have been identified as major risk factors that can compound the risk of liver injury in people with hereditary (HFE) haemochromatosis. The prospect of modifying genes that may contribute to the clinical expression of the disease is the subject of ongoing research. Treatment with phlebotomy remains the first-line therapy, and if instigated early leads to a normal life expectancy. A healthy, well-balanced diet is recommended to be incorporated as part of the ongoing management of the disease.
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PMID:Haemochromatosis: a clinical update for the practising physician. 2972 88