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PubMed2003

Current directions in hemochromatosis research: towards an understanding of the role of iron overload and the HFE gene mutations in the development of clinical disease.

Since the discovery of a candidate gene (HFE) thought to be involved in the development of hereditary hemochromatosis, there has been much interest in the potential use of genetic testing as a screening tool for the disease in the general population. However, a recent study suggests that less than 1% of subjects who are homozygous for the gene mutations will go on to develop the full-blown disease of hereditary hemochromatosis, historically termed "bronzed diabetes." The study also suggests that homozygotes have no higher risk of mortality or of any clinically significant morbidity than normal control subjects. This conclusion contradicts earlier findings that linked iron overload and HFE mutations to a number of devastating diseases, including cardiovascular disease, diabetes, and cancer.

Genetic Predisposition to Disease↗
PubMed2003

Linked linear amplification for simultaneous analysis of the two most common hemochromatosis mutations.

BACKGROUND: Two mutations in HFE, G845A (amino acid substitution C282Y) and C187G (H63D), are associated with hereditary hemochromatosis. We developed and validated a novel method, linked linear amplification (LLA), for detection of these two mutations. METHODS: Two segments of HFE were amplified by a multiplex LLA reaction that generated biotinylated LLA products. Aliquots of the multiplex LLA reaction were captured in microwells by hybridization to immobilized allele-specific oligonucleotides (ASOs). One wild-type and one mutant ASO represented the DNA sequence at each of the two mutation sites. Hybridization was detected by a streptavidin-horseradish peroxidase-based colorimetric method. Genotypes obtained by LLA and PCR-restriction fragment length polymorphism (PCR-RFLP) methods for 320 individuals were compared. RESULTS: The amplified samples included the following genotypes as determined by PCR-RFLP: wild-type 282 and 63 codons (n = 105), C282Y homozygous mutant (n = 54), C282Y heterozygous (n = 52), H63D homozygous mutant (n = 17), H63D heterozygous (n = 59), and compound H63D and C282Y heterozygous mutant (n = 33). There was complete concordance between the results obtained by LLA and those obtained by PCR-RFLP analysis. The presence of another HFE mutation, A193T (encoding S65C), did not interfere with genotyping at codon 63. CONCLUSIONS: LLA provides a reliable method to detect the common mutations in HFE that cause hereditary hemochromatosis.

Amino Acid Substitution↗
PubMed2006

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.

Antimicrobial Cationic Peptides↗
PubMed2002

Analysis of HLA-A antigens and C282Y and H63D mutations of the HFE gene in Brazilian patients with hemochromatosis.

The hemochromatosis gene, HFE, is located on chromosome 6 in close proximity to the HLA-A locus. Most Caucasian patients with hereditary hemochromatosis (HH) are homozygous for HLA-A3 and for the C282Y mutation of the HFE gene, while a minority are compound heterozygotes for C282Y and H63D. The prevalence of these mutations in non-Caucasian patients with HH is lower than expected. The objective of the present study was to evaluate the frequencies of HLA-A antigens and the C282Y and H63D mutations of the HFE gene in Brazilian patients with HH and to compare clinical and laboratory profiles of C282Y-positive and -negative patients with HH. The frequencies of HLA-A and C282Y and H63D mutations were determined by PCR-based methods in 15 male patients (median age 44 (20-72) years) with HH. Eight patients (53%) were homozygous and one (7%) was heterozygous for the C282Y mutation. None had compound heterozygosity for C282Y and H63D mutations. All but three C282Y homozygotes were positive for HLA-A3 and three other patients without C282Y were shown to be either heterozygous (N = 2) or homozygous (N = 1) for HLA-A3. Patients homozygous for the C282Y mutation had higher ferritin levels and lower age at onset, but the difference was not significant. The presence of C282Y homozygosity in roughly half of the Brazilian patients with HH, together with the findings of HLA-A homozygosity in C282Y-negative subjects, suggest that other mutations in the HFE gene or in other genes involved in iron homeostasis might also be linked to HH in Brazil.

Adult↗
PubMed2005

Hemochromatosis (HFE) gene mutations in Brazilian chronic hemodialysis patients.

Patients with chronic renal insufficiency (CRI) have reduced hemoglobin levels, mostly as a result of decreased kidney production of erythropoietin, but the relation between renal insufficiency and the magnitude of hemoglobin reduction has not been well defined. Hereditary hemochromatosis is an inherited disorder of iron metabolism. The importance of the association of hemochromatosis with treatment for anemia among patients with CRI has not been well described. We analyzed the frequency of the C282Y and H63D mutations in the HFE gene in 201 Brazilian individuals with CRI undergoing hemodialysis. The analysis of the effects of HFE mutations on iron metabolism and anemia with biochemical parameters was possible in 118 patients of this study (hemoglobin, hematocrit, ferritin levels, transferrin saturation, and serum iron). A C282Y heterozygous mutation was found in 7/201 (3.4%) and H63D homozygous and heterozygous mutation were found in 2/201 (1.0%) and 46/201 (22.9%), respectively. The allelic frequencies of the HFE mutations (0.017 for C282Y mutation and 0.124 for H63D mutation) did not differ between patients with CRI and healthy controls. Regarding the biochemical parameters, no differences were observed between HFE heterozygous and mutation-negative patients, although ferritin levels were not higher among patients with the H63D mutation (P = 0.08). From what we observed in our study, C282Y/H63D HFE gene mutations are not related to degrees of anemia or iron stores in CRI patients receiving intravenous iron supplementation (P > 0.10). Nevertheless, the present data suggest that the H63D mutation may have an important function as a modulating factor of iron overload in these patients.

Adolescent↗
PubMed2001

Role of hemochromatosis C282Y and H63D mutations in HFE gene in development of type 2 diabetes and diabetic nephropathy.

OBJECTIVE: In patients with clinical hemochromatosis, the frequency of diabetes ranges from 20 to 50%, and the heterozygosity for the C282Y mutation in the HFE gene might be associated with an increased risk for diabetes. There are also some reports that suggest that iron overload might cause diabetic nephropathy. RESEARCH DESIGN AND METHODS: We performed an association study to assess the role of the C282Y and H63D mutations in the HFE gene as a risk factor for type 2 diabetes and diabetic nephropathy. Altogether, 563 patients with type 2 diabetes were included in the study. In the analyzed group, 108 patients had overt proteinuria, 154 had microalbuminuria, and 301 had normoalbuminuria. Among the patients with normoalbuminuria, only those with known diabetes duration > or = 10 years were considered normoalbuminuric (n = 162). A total of 196 unrelated healthy subjects were used as a control group. All subjects were genotyped for C282Y and H63D using the polymerase chain reaction-based protocol. RESULTS: There was an increased frequency of 282Y allele carriers among patients with type 2 diabetes versus healthy control subjects (OR 5.3, 95% CI 1.6-17.3). We observed an increased frequency of the 63D allele carriers among patients with diabetic nephropathy (1.8, 1.2-2.8). CONCLUSIONS: In conclusion, our study is the first to indicate that being a carrier of the H63D hemochromatosis mutation is a risk factor for nephropathy in type 2 diabetic patients. We also confirmed previous observations that the frequency of the 282Y mutation was higher in patients with type 2 diabetes than it was in the general population of healthy subjects.

Age of Onset↗
PubMed2005

Occult celiac disease prevents penetrance of hemochromatosis.

AIM: To report a patient with C282Y homozygocity, depleted body iron and intestinal atrophy caused by celiac disease (CD) who experienced resolution of the enteropathy with subsequent normalization of iron metabolism upon gluten-free diet. METHODS: To obtain information on the tissue distribution and quantitative expression of proteins involved in duodenal iron trafficking, we determined the expression of divalent-metal transporter 1 (DMT1), ferroportin 1 (FP1) and transferrin receptor (TfR1) by means of immunohistochemistry and real-time PCR in duodenal biopsies of this patient. RESULTS: Whereas in hereditary hemochromatosis patients without CD, DMT1 expression was up-regulated leading to excessive uptake of iron, we identified a significant reduction in protein and mRNA expression of DMT1 as a compensatory mechanism in this patient with HH and CD. CONCLUSION: Occult CD may compensate for increased DMT1 expression in a specific subset of individuals with homozygous C282Y mutations in the hemochromatosis (HFE) gene, thus contributing to the low penetrance of HH.

Aged↗
PubMed2004

Evolution of untreated hereditary hemochromatosis in the Busselton population: a 17-year study.

OBJECTIVE: To describe the evolution of biochemical and clinical features during a 17-year period in untreated subjects homozygous for the C282Y mutation in the hemochromatosis gene. SUBJECTS AND METHODS: In 1998, 12 subjects from Busselton, Australia, were newly diagnosed as being homozygous for the C282Y mutation. We determined transferrin saturation and ferritin values and retrieved clinical information from the 1981, 1994, and 1998 population surveys for 10 of these subjects. RESULTS: The median age of the 10 subjects in 1981 was 30 years. Between 1981 and 1998, the median transferrin saturation value increased from 42% to 76%. Six subjects with elevated transferrin saturation in 1998 had values less than 45% in 1981. Between 1981 and 1998, the median serum ferritin levels increased from 271 microg/L to 593 microg/L. Serum ferritin levels increased in 4 subjects, remained relatively constant in 4, and decreased in 2. Of 5 subjects with serum ferritin levels lower than 200 microg/L in 1981, 4 had no increase in these levels between 1981 and 1998. Of 4 subjects with persistently elevated serum ferritin levels greater than 500 microg/L, 3 developed stage III or IV fibrosis, based on the METAVIR scoring system. CONCLUSIONS: Untreated C282Y homozygous subjects had progressively increasing transferrin saturation values but marked variation in serum ferritin levels during a 17-year period before diagnosis. A screening threshold for serum transferrin saturation values greater than 45% at an early stage in adult life could fail to detect 60% of C282Y homozygotes who subsequently develop biochemical features of hemochromatosis.

Adult↗
PubMed2001

Vibrio vulnificus septicemia in a patient with the hemochromatosis HFE C282Y mutation.

Vibrio vulnificus is an extremely invasive gram-negative bacillus found in marine waters that causes overwhelming bacteremia and shock that is associated with high mortality. Impaired iron metabolism has been implicated in the susceptibility to V vulnificus bacterial infections. We report a case of fatal V vulnificus sepsis in a 56-year-old man who died within 1 to 3 days after consuming raw seafood. At autopsy, he was found to have micronodular cirrhosis and iron overload. Postmortem genetic analysis revealed the presence of the hemochromatosis gene (HFE) C282Y mutation. To our knowledge, this is this first documented fatal case of V vulnificus infection in a patient proven to carry the HFE C282Y mutation. Because this patient was heterozygous for the major hereditary hemochromatosis mutation and was not previously diagnosed with clinical iron overload, the spectrum of clinical susceptibilities to V vulnificus infection may include carriers of the C282Y mutation.

Animals↗
PubMed1999

The C282Y mutation causing hereditary hemochromatosis does not produce a null allele.

Targeted mutagenesis was used to produce two mutations in the murine hemochromatosis gene (Hfe) locus. The first mutation deletes a large portion of the coding sequence, generating a null allele. The second mutation introduces a missense mutation (C282Y) into the Hfe locus, but otherwise leaves the gene intact. This mutation is identical to the disease-causing mutation in patients with hereditary hemochromatosis. Mice carrying each of the two mutations were bred and analyzed. Homozygosity for either mutation results in postnatal iron loading. The effects of the null mutation are more severe than the effects of the C282Y mutation. Mice heterozygous for either mutation accumulate more iron than normal controls. Interestingly, although liver iron stores are greatly increased, splenic iron is decreased. We conclude that the C282Y mutation does not result in a null allele.

Alleles↗
PubMed2000

[Genetic hemochromatosis and the HFE gene].

The discovery of the HFE gene has lead to considerable improvement in the understanding and the management of genetic hemochromatosis. More than 90% of well-defined patients are homozygous for the C282Y mutation, and genetic testing has become an important diagnostic tool. The significance of the other mutations in the HFE gene remain controversial: only C282Y/H63D compound heterozygotes could present with a phenotype compatible with hemochromatosis, but with a mild expression and a low penetrance. The link between iron overload and HFE mutation is explained by the interaction between HFE protein, beta-2-microglobulin and transferrin receptor, which is abolished by the C282Y mutation, but is not yet fully understood.

HLA Antigens↗
PubMedDate not supplied

Frequency of the hemochromatosis C282Y and H63D mutations in a Polish population of Slavic origin.

BACKGROUND: Hereditary hemochromatosis is one of the most common monogenic diseases among Caucasians. The most frequent mutation causing hemochromatosis is C282Y in the HFE gene, the highest frequency of which has been observed in populations of Celtic origin. There are no studies providing information about the frequency of the C282Y and H63D mutations in the HFE gene in populations of Slavic origin. MATERIAL AND METHODS: We collected 871 healthy unrelated subjects in Poland to assess the relevant frequencies. Each subject was genotyped for the C282Y and H63D mutations using a PCR-based protocol. RESULTS: Among the analysed subjects 6.0% were CY heterozygotes, and only one person was YY homozygote. The observed frequency of the 282Y allele was 3.1%. The frequency of the D allele of the H63D polymorphism was 16.2%. There were 13 (1.5%) compound heterozygotes for C282Y and H63D found in the analysed group. CONCLUSION: The high frequency of the Y allele in this Polish population of non-Celtic origin may indicate an early introduction of this mutation through admixture with a strong positive selection.

Alleles↗
PubMedDate not supplied

Heterozygosity for the H63D mutation in the hereditary hemochromatosis (HFE) gene may lead into severe iron overload in beta-thalassemia minor: observations in a thalassemic kindred.

Heterozygosity for beta-thalassemia (minor) by itself does not lead into iron overload; however, when it is inherited together with a homozygous state for either the H63D or the C282Y mutations of the hereditary hemochromatosis gene (HFE gene), iron overload may ensue. We describe here a kindred in which the propositus, being heterozygote for beta-thalassemia and the H63D mutation of the HFE gene, developed severe iron overload and in turn, chronic liver failure with portal hypertension. Other members of the family with either beta-thalassemia or heterozygous for the H63D gene mutation did not develop iron overload. The interaction between beta-thalassemia and hereditary hemochromatosis is briefly discussed and speculations about other possible genetic mutations leading into familial iron loading are done.

Adult↗
PubMed2002

[Relationship between HFE gene and hereditary hemochromatosis].

HFE gene is a major histocompatibility complex class I-like gene, which was identified as a candidate gene for hemochromatosis in 1996. The proposed role for HFE is its part in the regulation of the interaction of the transferrin receptor with transferrin. Hemochromatosis, the common autosomal recessive disease of iron overload, affects at least 1 in 300 Caucasians. The identification of the C282Y mutation in the HFE gene has led to population screening studies. Much of this work has also included the analysis of a second mutation, H63D, which appears to have a low penetrability. HFE protein was recently found to coprecipitate with the transferrin receptor and to affect the reaction between transferrin and the transferrin receptor. Functional data suggest that the mutation C282Y abolishes the association of the HFE protein with beta 2-microglobulin (beta 2M), making the complex unable to reach the cell surface. Clearly, if the mutation protein is unable to reach the cell surface, this regulatory feature is missing. The role of a second mutation in the HFE gene, H63D, is less clear. Current data suggest that this mutation protein can associate with beta 2-microglobulin and does reach the cell surface and that the defect lies in a failure to modify the affinity of the transferrin receptor for transferrin. This does not explain the low degree of penetrability associated with this mutation.

Gene Frequency↗
PubMed2003

Association of heterozygous hemochromatosis C282Y gene mutation with hand osteoarthritis.

OBJECTIVE: To determine if there is an association between radiographic osteoarthritis (OA) of the hand and the presence of hemochromatosis HFE gene mutations. METHODS: One hundred seventy-six patients with radiographic OA of the hand were randomly selected from an academic rheumatology practice. We measured serum transferrin saturation (TS) and ferritin levels, and genotyped for the presence of the 2 common HFE mutations, C282Y and H63D. The prevalences of HFE mutations in these patients were compared to those in a hemochromatosis screening study from the same primary care patient base. RESULTS: There was a significantly increased prevalence of the C282Y mutation in the OA population compared to the unselected controls (12.5 vs 7.8%; p = 0.029). The prevalence of C282Y in OA was higher among older patients: 15.75% in the group older than 65 years versus 4.08% in the younger group. The mean TS level was higher among OA patients who were heterozygous for C282Y compared to those who lacked both HFE mutations (35.75 vs 25.93%; p < 0.0001). This difference was also found in the general population. CONCLUSION: This is the first report to show an increased risk of OA among individuals who are heterozygous for the C282Y HFE mutation. The increase in this mutation in patients older than 65 suggests that this is associated with a late onset subset of OA. If this association is substantiated by larger randomized controlled studies, it could have major therapeutic implications in the development of specific therapy directed at individuals heterozygous for C282Y HFE mutation.

Aged↗
PubMed2005

Hereditary hemochromatosis in a Brazilian university hospital in São Paulo State (1990-2000).

Hereditary hemochromatosis (HH) is the most common genetic disease among individuals of European descent. Two mutations (845G-->A, C282Y and 187C-->G, H63D) in the hemochromatosis gene (HFE gene) are associated with HH. About 85-90% of patients of northern European descent with HH are C282Y homozygous. The prevalence of HH in the Brazilian population, which has a very high level of racial admixture, is unknown. The aims of the present study were to identify individuals with diagnostic criteria for HH among patients with a body iron overload attended at the university hospital of the Faculty of Medicine of Ribeirao Preto from 1990 to 2000, and to evaluate the prevalence of HFE mutations. We screened first-degree relatives for HFE mutations. Four of 72 patients (three men and one woman, mean age 47 years) fulfilled the criteria for HH. HFE mutations were studied in three patients [two C282Y homozygotes (patients 1 and 2) and one H63D heterozygote]. Patient 1 had four children (all C282Y heterozygotes with no iron overload) and seven brothers and sisters: two sisters (66 and 76 years old) were C282Y homozygotes and both had an iron overload (a liver biopsy in one showed severe iron deposits), one sister (79 years old) was a compound heterozygote with no iron overload, one brother (78 years old) was a C282Y heterozygote with no iron overload, two individuals were H63D heterozygotes (one brother, 49 years old, obese, with a body iron overload and abnormal liver enzymes - a biopsy showed non-alcoholic steatohepatitis, and one 70-year-old sister with no iron overload). Patient 2 had two children (22 and 24 years old who were C282Y heterozygotes with no iron overload) but no brothers or sisters. These results showed that HH was uncommon among individuals attended at our hospital, although HFE mutations were found in all patients. Familial screening is valuable for the early diagnosis of individuals at risk since it allows treatment to be initiated before the onset of the clinical manifestations of organ damage associated with HH.

Adult↗