A study of 609 HLA haplotypes marking for the hemochromatosis gene: (1) mapping of the gene near the HLA-A locus and characters required to define a heterozygous population and (2) hypothesis concerning the underlying cause of hemochromatosis-HLA association.

We compared 609 haplotypes carrying the idiopathic hemochromatosis allele with 475 control haplotypes. Four haplotypes were more frequent in hemochromatosis: A3, B7 (actually A3, CW., B7, Bfs, DR2); A3, B14 (actually A3, CW., B14, BfF, DRW6); A11, B35; and A11, B5. The linkage disequilibrium for A3, B7 and A3, B14 (and probably also for A11, B5) was undeniably stronger in hemochromatosis than in controls. Two haplotypes--A3, B12 and A3, B15--were more frequent in hemochromatosis, without linkage disequilibrium. Four haplotypes in linkage disequilibrium in hemochromatosis--i.e., A2, B12; A1, B8; A9, B7; and A29, B12--were also found to have the same frequency and strength of linkage in controls. The dual observation (1) that haplotypes carrying A3 without either B7 or B14 were highly significantly more frequent in hemochromatosis than in controls and (2) that haplotypes carrying B7 or B14 but not A3 had the same frequency in hemochromatosis and controls led to the formal conclusion that only A3 is an independent marker for the hemochromatosis allele, B7 and B14 being involved only owing to the haplotypic mode of marking; the hemochromatosis allele can thus be mapped closer to locus A than to locus B. Our findings fit well with the hypothesis that the hemochromatosis mutation was a rare if not unique event that produced an ancestral HLA marking that was subsequently modified by recombinations and geographical scattering due to migrations.     

HLA determinants in an Australian population of hemochromatosis patients and their families.

The frequencies of different HLA-A and -B alleles in 77 Australian patients with hemochromatosis have been compared with frequencies of HLA alleles not associated with hemochromatosis in 63 of their heterozygous relatives and with published population frequencies. As for all other populations reported, an association of HLA-A3 and HLA-B7 with the disease was found. A weak association with HLA-B12 was also detected. No other significant positive or negative associations with HLA alleles were detected. In addition, HLA-A2 and -B12 were in significant linkage disequilibrium in patients but not in controls, which may indicate a new mutation or recent recombination between HLA-A and hemochromatosis either in our patient group or in the founding population. HLA-A1 and -B8 and HLA-A29 and -B12 were in linkage disequilibrium in controls but not in patients, suggesting that this population is not segregating a hemochromatosis allele on either of these haplotypes. Genetic linkage analysis using the program LIPED showed strong linkage in 23/24 families, most of which had additional HLA alleles (other than A3 and B7) associated with hemochromatosis. This provides evidence for a single hemochromatosis locus, possibly with more than one allele.     

Acceptance of neonatal genetic screening for hereditary hemochromatosis by informed parents

The aim of this study was to assess attitudes to neonatal genetic screening for hereditary hemochromatosis. A total of 135 consecutive, pregnant women and their partners attending a hospital antenatal clinic in the Australian Capital Territory were given detailed written and verbal information about potential risks and benefits of neonatal genetic screening. Issues such as uncertainty of disease expression, confidentiality, genetic discrimination, and storage of genetic data were addressed. Attitudes were assessed by interview and questionnaire. There was a high level of acceptance for neonatal genetic screening in general (99%) and for hemochromatosis in particular (91.5%). There was no association of prior knowledge of hemochromatosis, family history of hemochromatosis, ethnicity, age, education, or occupation class with nonacceptance. Of the subjects, 39.5% reported feeling "a little anxious" about the prospect of screening their infants, although only 5.4% reported feeling "very anxious." Reasons given for nonacceptance of screening included inability of the child to give informed consent, insufficient evidence that diagnosis of hemochromatosis in childhood is beneficial, risk of discrimination on genetic grounds, lack of agreement between partners, and privacy issues. These data suggest that an Australian neonatal genetic screening program for hemochromatosis is likely to be accepted by this and similar groups of subjects, but there should be an opportunity for parents who object to screening to opt out of any such program.     

Mapping the locus for hereditary hemochromatosis: localization between HLA-B and HLA-A.

We studied a family with HLA-linked hereditary hemochromatosis in which an informative recombination occurred within the HLA region. The father, an obligate heterozygote for hereditary hemochromatosis, had HLA haplotypes A2,B13 and A11,B27. The mother, also an obligate heterozygote, had HLA haplotypes A29,B44 and A2,B7. Three haplotypes were found among three homozygous affected offspring. Two affected siblings were HLA-identical with haplotypes A2,B13 and A29,B44. The proband had HLA haplotypes A2,B13 and A2,B44, the latter a recombinant haplotype inherited from her mother. Since the maternal hemochromatosis allele was linked to the A29,B44 haplotype, and since the proband has hemochromatosis, the maternal hemochromatosis allele was transmitted to the proband with the B44 antigen. This is the first known example of recombination in an individual with HLA-linked hemochromatosis in whom the hemochromatosis allele appeared to segregate with the HLA-B antigen instead of the -A antigen. The possibility of either a double reciprocal recombination event or a gene conversion event cannot be excluded. Combined with earlier observations of segregation of the hemochromatosis allele with the A locus in HLA recombinants, the findings in this pedigree map the hemochromatosis locus between the HLA-B and HLA-A loci rather than outside the HLA region.     

Idiopathic hemochromatosis: demonstration of homozygous-heterozygous mating by HLA typing of families

Summary In five families with idiopathic (hereditary) hemochromatosis, clinical and biochemical expression of the disease occurred in offspring of probands, suggesting an autosomal dominant mode of inheritance. However, HLA typing of subjects indicated that a homozygous-heterozygous mating almost certainly had occurred in four of the five families, resulting in homozygous offspring. Thus, in these families inheritance of the hemochromatosis trait was best explained in terms of an autosomal recessive or intermediate mode of inheritance. This study demonstrates the value of HLA typing in identifying homozygous-heterozygous matings in hemochromatosis families.     

A candidate gene for hemochromatosis: frequency of the C282Y and H63D mutations

The gene whose alteration causes hereditary hemochromatosis (HFE according to the international nomenclature) was, more than 20 years ago, shown to map to 6p21.3. It has since escaped all efforts to identify it by positional cloning strategies. Quite recently, a gene named HLA-H was reported as being responsible for the disease. Two missense mutations, Cys282Tyr (C282Y) and His63Asp (H63D), were observed, but no proof was produced that the gene described is the hemochromatosis gene. To validate this gene as the actual site of the alteration causing hemochromatosis, we decided to look for the two mutations in 132 unrelated patients from Brittany. Our results indicate that more than 92% of these patients are homozygous for the C282Y mutation, and that all 264 chromosomes but 5 carry either mutation. These findings confirm the direct implication of HLA-H in hemochromatosis. Received: 16 December 1996 / Accepted: 13 May 1997     

A rapid PCR-SSP assay for the hemochromatosis-associated Tyr250Stop mutation in the TFR2 gene

Several genes associated with hemochromatosis and primary iron overload have been identified. Mutations in the HFE gene have been detected in 60-100% of hemochromatosis patients of northern, central, and western European descent, although the frequencies of these mutations vary among racial and ethnic groups. Recently, a mutation in the gene encoding transferrin receptor-2 (exon 6, nucleotide 750 C --> G; Y250X) was detected by a PCR-restriction fragment length polymorphism (RFLP) method in Sicilians with hemochromatosis. We describe a modification of the original assay in which the sequence-specific priming PCR assay does not require the use of restriction endonuclease. The modified assay is robust and cost-efficient, and may be more useful for large-scale population studies because it can be performed rapidly on DNA extracted from buccal swabs.     

Isoenzyme composition of human plasma monoamine oxidase in normal subjects and in fibrotic liver disease.

Hydroxyapatite column chromatography elution profile reveals characteristic differences between monoamine oxidase (MAO) isolated from normal human plasma and from patients with hemochromatosis having hepatic fibrosis. In normal plasma, the alpha form constitutes about 84% of the enzyme, with the remainder in the beta and gamma forms. By contrast, in hemochromatosis there is less alpha form (less than 40%), an additional alpha1 form (about 20%) which was eluted immediately after alpha form, increased beta form (more than 25%), and no significant difference in gamma form. When calculated on the basis of total amount per liter, hemochromatosis is characterized by elevation of beta form (3- to 10-fold) and the presence of alpha1. These results also appear to indicate that the multiple forms separated by hydroxyapatite column chromatography represent true multiplicity of human plasma MAO in vivo.     

Celtic origin of the C282Y mutation of hemochromatosis

The main hereditary hemochromatosis mutation C282Y in the HFE gene was recently described, and the C282Y frequencies were reported for various European populations. The aim of this synthesis is to compile the Y allele frequencies of the C282Y mutation for 40 European populations. The most elevated values are observed in residual Celtic populations in Ireland, the United Kingdom, and France, in accordance with the hypothesis of Simon et al. (1980) concerning a Celtic origin of the hereditary hemochromatosis mutation.     

Hemochromatosis gene sequence deviations in German patients with porphyria cutanea tarda

Patients with porphyria cutanea tarda (PCT) reveal a susceptibility to reversible inactivation of hepatic uroporphyrinogen decarboxylase, which might be triggered by alcohol, hepatitis C virus infection, and iron overload. Inherited factors that may predispose to clinically overt PCT also include sequence deviations in the HFE gene that is mutated in classical hemochromatosis. Here, we studied the prevalence of both common and rare hemochromatosis gene variations in 51 PCT patients and 54 healthy controls of German origin. The frequency of the common HFE gene mutation C282Y was 15.7 % in PCT patients and 2.8 % in healthy control individuals (P < 0.001). By contrast, the frequencies of the common H63D mutation did not differ, and the allele frequencies of the less frequently observed sequence deviations as substitution S65C in the HFE gene and mutation Y250X in the TFR2 gene underlying hemochromatosis type 3 (HFE3) were < 0.02 both in PCT patients and controls. Our results comprise the first molecular studies of both common and rare hemochromatosis gene variants in German PCT patients, indicating a significant role of the C282Y mutation in the pathogenesis of PCT.     

Serum ferritin as a marker of affection for genetic hemochromatosis

A bivariate segregation analysis of genetic hemochromatosis with serum ferritin concentration was undertaken to examine the pleiotropic effect of the hemochromatosis locus on each of the two phenotypes, in an ascertained sample of families from Brittany, France. The gene was recessive with respect to both phenotypes, and the estimated gene frequency in the general population was 0.054. Although the ferritin concentration was corrected for the linear relationship with age among controls, there was a residual correlation with age among male family members, consistent with the progressive increase in body iron stores among hemochromatosis homozygotes. This genotype-specific relationship with age illustrates the importance of incorporating interaction effects into analytic models, and suggests that even as a better indicator of progress of disease, rather than liability to disease, serum ferritin concentration serves well to distinguish hemochromatosis homozygotes from alternate genotypes in a family study.     

Tropical pyomyositis of the abdominal wall musculature mimicking acute abdomen.

Hemochromatosis is an autosomal recessive genetic disorder that occurs with high prevalence in populations of European origin. The gene that is abnormal in hemochromatosis is found on the short arm of chromosome 6 in close proximity (approximately 1 centimorgan) to HLA-A, but the product coded for by that gene is unknown. The pathogenetic mechanism in hemochromatosis is that of continued, excessive absorption of dietary iron with loss of normal control mechanisms, leading to a gradual but vast expansion of storage iron as ferritin and especially as hemosiderin. Through mechanisms that probably include peroxidation of lipid membranes, the excess iron injures hepatocytes, islet B cells, gonadotropes in the anterior pituitary, myocardium, synovial cells, and chondrocytes, and probably other cells and tissues as well. Most patients with hemochromatosis remain undiagnosed throughout life. Removal of the excess iron by phlebotomy will prevent all of the complications of hemochromatosis when begun early and will significantly improve survival in virtually all patients. It is important, therefore, that the diagnosis of hemochromatosis be considered much more frequently in clinical medicine in order that this effective therapy be utilized.     

A haplotype and linkage disequilibrium analysis of the hereditary hemochromatosis gene region

Hereditary hemochromatosis is a recessive disease of iron metabolism widely distributed among people of European descent. Most patients have inherited the causative mutation from a single ancestor. In the course of cloning the hemochromatosis gene, genotypes were generated for these samples at 43 microsatellite repeat markers that span the 6.5-Mb hemochromatosis gene region. The data used to reconstruct the ancestral haplotype across the hemochromatosis gene region are presented in this paper. Portions of the ancestral haplotype were present on 85% of patient chromosomes in this sample and ranged in size from approximately 500 kb to greater than 6.5 Mb. Only one marker, D6S2239, was identical by descent on all of the patient chromosomes containing the ancestral mutation. In contrast, only 3 of the 128 control chromosomes, or 2.3%, carried the ancestral mutation and the surrounding ancestral haplotype. To test new methods for gene finding using linkage disequilibrium we analyzed the genotypic data with a multilocus maximum likelihood method (DISMULT) and a single point method (DISLAMB), both written to analyze data generated from multi-allelic markers. The maximum value from DISLAMB analysis occurred at marker D6S2239, which is less than 20 kb from the hemochromatosis gene HFE, consistent with the haplotype analysis. The peak of the multi-point analysis was 700 kb from HFE, possibly due to the nonuniform recombination rates within this large region. The recombination rate appears to be lower than expected centromeric of the HFE gene. Received: 10 June 1997 / Accepted: 4 December 1997     

Iron chelation with deferasirox in a patient with de-novo ferroportin mutation

Ferroportin disease is a rare type of autosomal dominantly inherited hemochromatosis caused with mutations in the ferroportin gene (SLC40A1). The patients characteristically have hyperferritinemia but normal transferin saturations. Herein, we present a 15-year-old female whose chief complaint was persistent nausea for the last one year. Extensive work-up including brain imaging revealed nothing to explain the etiology of nausea. The serum ferritin level of 1474 ng/mL was suggestive for hemochromatosis syndromes and the molecular testing revealed de-novo c.485_487delTTG (P.Val162del) ferroportin gene mutation. Mild hepatic iron loading, in addition to the cumbersome nausea were accepted as indications for chelation treatment in this particular patient and deferasirox was initiated (10 mg/kg/day) since family did not consent for phlebotomy. Deferasirox was stopped by the 9th month of initiation, since nausea subsided and hepatic iron content was normalized, in order to prevent over chelation. There are no well-established guidelines for the chelation of patients with hereditary hemochromatosis syndromes. However, lifelong monitorization for iron loading and re-initiation of chelation when necessary was planned in our patient.     

Increased urinary excretion of 8-iso-prostaglandin F2alpha in patients with HFE-related hemochromatosis: a case-control study

The hypothesis according to which iron overload could be harmful has been extensively and controversially discussed in the literature. One underlying pathological mechanism may be elevated oxidative stress. Thus, we studied the correlation between hemochromatosis and an established marker of oxidative stress, 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha, iPF2alpha-III, 15-F2t-IsoP). We enrolled 21 patients with hemochromatosis, positive for the homozygous C282Y mutation in the HFE gene, and 21 healthy controls frequency-matched by age and gender in a case-control study design. The objective was to show that iron overload in HFE-related hemochromatosis is associated with increased oxidative stress assessed through 8-iso-PGF(2alpha) urinary excretion, and that oxidative stress is impacted by iron-removal treatment (phlebotomy). Study parameters were transferrin saturation, 8-iso-PGF(2alpha) urine excretion, transferrin, ferritin, serum iron, and vitamins A and E for all participants. Iron concentration in the liver and non-transferrin-bound iron were measured in patients only. We found a significant difference in 8-iso-PGF2alpha in patients (245 [interquartile range 157-348] pg/mg creatinine) compared with controls (128 [106-191] pg/mg creatinine, P = 0.002). Vitamin A was significantly reduced in cases (0.34 [0.25-1.83] microg/ml compared to 3.00 [2.11-3.39] microg/ml, P < 0.001), while vitamin E did not show a significant difference in cases (14.7 [11.5-18.1] microg/ml) compared with controls (14.9 [13.1-19.2] microg/ml, P = 0.52). After phlebotomy treatment and normalization of the iron parameters in the hemochromatosis group, serum vitamin A levels were significantly increased (1.36 [1.08-1.97] microg/ml, P = 0.035 vs. baseline, P < 0.001 vs. controls) and 8-iso-PGF2alpha urinary excretion was lowered to control levels (146 [117-198] pg/mg creatinine, P = 0.38 vs. controls). In our study, HFE-related hemochromatosis was associated with increased oxidative stress and hypovitaminemia A in C282Y homozygotes. The increased oxidative stress was reversible by normalization of the iron load by phlebotomy. Thus, phlebotomy is an effective and adequate means for reducing oxidative stress in these patients.     

Psychosocial impact of C282Y mutation testing for hemochromatosis

The aim of this study was to investigate the psychological effects of genetic testing for hemochromatosis. Study participants included cases discovered through a population screening study in 5211 voluntary blood donors (n = 25) and patients referred for diagnostic evaluation for hemochromatosis (n = 117). Participants completed questionnaires (Spielberger State-Trait Anxiety Index, Medical Outcomes Survey Short Form 36) before and after genetic testing. A subset of participants from the screening study was also interviewed 1 year after testing (Feelings About Test Results Measure). Additional questions included data on insurance applications, time off from work, and family issues. Anxiety significantly decreased in homozygotes and heterozygotes after genetic testing and remained constant in C282Y mutation-negative cases. Vitality and physical composite scores improved after genetic testing. There were no significant deleterious psychological effects of genetic testing on anxiety and on mental and physical health status. There were no negative effects discovered on insurance or time off work. This study has not demonstrated deleterious effects of genetic testing for hemochromatosis on anxiety, mental health and physical health status, insurance, or time off from work. Genetic testing for hemochromatosis is well accepted and should not be discouraged on the basis of potential adverse psychosocial effects.     

Idiopathic hemochromatosis and chromosomal damage.

Spontaneous and radiation-induced chromosome damage in cultured lymphocytes was examined in a pilot study of 11 patients with idiopathic hemochromatosis and matched controls. Increased frequencies of chromosome breaks were found in the patients, both spontaneously and after exposure to ionizing radiation, but the differences between patients and controls were not statistically significant (p greater than 0.05) when individual data were analyzed. When pooled (group) data for patients and controls were compared, significant increases in spontaneous and radiation-induced chromosome breaks were found among the patients. The results suggest that iron overload may lead to chromosome damage in idiopathic hemochromatosis.     

Hereditary hemochromatosis

The advent of the genetics era has profoundly changed the way we look at iron related diseases, particularly hemochromatosis. New discoveries have challenged historical concepts about the disease, such as its monogenic nature, intestinal origin or complete phenotypic penetrance. This review presents a new concept of hemochromatosis which stems from the idea that, beyond their genetic diversities, all known hemochromatoses have in common the same metabolic abnormality: the genetically determined failure to prevent unneeded iron from entering the circulatory pool. Inappropriate levels of hepcidin, the iron hormone, appear now as the central pathogenic event in all forms of hemochromatosis: depending on the protein involved, and its effect on hepatic production of hepcidin, the phenotype varies, ranging from massive early-onset iron loading with severe organ disease (e.g., associated with homozygous mutations of hemojuvelin or hepcidin itself) to the milder late-onset phenotype characterizing the classic and highly prevalent HFE-related form or the rare transferrin receptor 2-related form. In vitro and in vivo studies will be needed to dissect the consequences of each hereditary hemochromatosis allele and increase our understanding of the precise contribution of each gene to the hereditary hemochromatosis phenotype.