The HLA-A1-B8 haplotype hitchhiking with the hemochromatosis mutation: does it affect the phenotype?

The ancestral haplotype markers HLA -A3 and B7 do not influence the likelihood of advanced hepatic fibrosis or cirrhosis in HFE hemochromatosis

Advanced hepatic fibrosis occurs in up to 25% of individuals with C282Y homozygous hemochromatosis. Our aim was to determine whether human leukocyte antigen (HLA)-A3 and B7 alleles act as genetic modifiers of the likelihood of advanced hepatic fibrosis. Between 1972 and 2013, 133 HFE C282Y homozygous individuals underwent clinical and biochemical evaluation, HLA typing, liver biopsy for fibrosis staging and phlebotomy treatment. Hepatic fibrosis was graded according to Scheuer as F0-2 (low grade hepatic fibrosis), F3-4 (advanced hepatic fibrosis), and F4 cirrhosis. We analysed associations between the severity of fibrosis and HLA-A3 homozygosity, heterozygosity or absence, with or without the presence of HLA-B7 using categorical analysis. The mean age of HLA-A3 homozygotes (n = 24), heterozygotes (n = 65) and HLA-A3 null individuals (n = 44) was 40 years. There were no significant differences between the groups for mean(± SEM) serum ferritin levels (1320 ± 296, 1217 ± 124, 1348 ± 188 [Formula: see text]g/L), hepatic iron concentration (178 ± 26, 213 ± 22, 199 ± 29 [Formula: see text]mol/g), mobilizable iron stores (9.9 ± 1.5, 9.5 ± 1.5, 11.5 ± 1.7 g iron removed via phlebotomy), frequency of advanced hepatic fibrosis (5/24[12%], 13/63[19%], 10/42[19%]) or cirrhosis (3/24[21%], 12/63[21%], 4/42[24%]), respectively. The presence or absence of HLA-B7 did not influence the outcome. Thus, HLA-A3 and HLA-B7 alleles are not associated with the risk of advanced hepatic fibrosis or cirrhosis in C282Y hemochromatosis.

Autoimmune Conditions in 235 Hemochromatosis Probands with HFE C282Y Homozygosity and Their First-Degree Relatives

We performed a retrospective study of autoimmune conditions (ACs) in 235 hemochromatosis probands at diagnosis by analyzing age, sex, ACs, history of first-degree family members with ACs (FH), diabetes, heavy ethanol consumption, elevated serum ALT/AST, nonalcoholic fatty liver disease, viral hepatitis, cirrhosis, iron removed to achieve iron depletion (QFe), and positivity for human leukocyte antigen (HLA) haplotypes A^∗01, B^∗08; A^∗02, B^∗44; A^∗03, B^∗07; A^∗03, B^∗14; and A^∗29, B^∗44. There were 138 men (58.7%). Median followup was 19.6 y. One or more of 19 ACs were diagnosed in each of 35 probands (14.9%). Prevalences of Hashimoto's thyroiditis, rheumatoid arthritis, and ankylosing spondylitis were 8.1% (95% CI: [5.1, 12.5]), 1.7% [0.6, 4.6], and 0.0085 [0.0015, 0.0337], respectively. Eighteen probands (7.7%) had a FH. Eight probands with ACs had 9 family members with ACs. In a logistic regression, ACs were less likely in men (odds ratio (OR) 0.3 [0.1, 0.6]) and more likely in probands with a FH (OR 4.1 [1.4, 11.8]). Overall ACs risk was not significantly associated with QFe or HLA haplotypes. Estimated survival of probands with and without ACs did not differ significantly. We conclude that ACs are common in hemochromatosis probands, especially women and probands with a FH.

Effects of highly conserved major histocompatibility complex (MHC) extended haplotypes on iron and low CD8+ T lymphocyte phenotypes in HFE C282Y homozygous hemochromatosis patients from three geographically distant areas

Hereditary Hemochromatosis (HH) is a recessively inherited disorder of iron overload occurring commonly in subjects homozygous for the C282Y mutation in HFE gene localized on chromosome 6p21.3 in linkage disequilibrium with the human leukocyte antigen (HLA)-A locus. Although its genetic homogeneity, the phenotypic expression is variable suggesting the presence of modifying factors. One such genetic factor, a SNP microhaplotype named A-A-T, was recently found to be associated with a more severe phenotype and also with low CD8⁺T-lymphocyte numbers. The present study aimed to test whether the predictive value of the A-A-T microhaplotype remained in other population settings. In this study of 304 HH patients from 3 geographically distant populations (Porto, Portugal 65; Alabama, USA 57; Nord-Trøndelag, Norway 182), the extended haplotypes involving A-A-T were studied in 608 chromosomes and the CD8⁺ T-lymphocyte numbers were determined in all subjects. Patients from Porto had a more severe phenotype than those from other settings. Patients with A-A-T seemed on average to have greater iron stores (p = 0.021), but significant differences were not confirmed in the 3 separate populations. Low CD8⁺ T-lymphocytes were associated with HLA-A*03-A-A-T in Porto and Alabama patients but not in the greater series from Nord-Trøndelag. Although A-A-T may signal a more severe iron phenotype, this study was unable to prove such an association in all population settings, precluding its use as a universal predictive marker of iron overload in HH. Interestingly, the association between A-A-T and CD8⁺ T-lymphocytes, which was confirmed in Porto and Alabama patients, was not observed in Nord-Trøndelag patients, showing that common HLA haplotypes like A*01–B*08 or A*03–B*07 segregating with HFE/C282Y in the three populations may carry different messages. These findings further strengthen the relevance of HH as a good disease model to search for novel candidate loci associated with the genetic transmission of CD8⁺ T-lymphocyte numbers.

Dupuytren's Contracture in Alabama HFE Hemochromatosis Probands

BACKGROUND

Dupuytren's contracture (DC) and HFE hemochromatosis occur in some of the same at-risk populations and present with similar comorbid conditions.

METHODS

We estimated DC prevalence in two cohorts of white Alabama hemochromatosis probands (294 C282Y homozygotes, 67 C282Y/H63D compound heterozygotes) in a retrospective study. We performed logistic regressions on DC using the following independent variables: age, body mass index, heavy ethanol consumption, serum ferritin, elevated serum AST/ALT, non-alcoholic fatty liver disease, viral hepatitis, cirrhosis, and diabetes.

RESULTS

One man and two women with C282Y homozygosity had DC (prevalence 1.02%; 95% CI 0.35%-2.96%). A man with C282Y/H63D had DC (prevalence 1.49%; 95% CI 0.26%-7.98%). DC occurred as an autosomal dominant trait in his kinship. In regression analyses, no single variable predicted DC. We observed no new DC cases after the diagnosis of hemochromatosis (mean follow-up 12.9 ± 7.5 years (1 SD), and 9.0 ± 5.1 years, respectively).

CONCLUSIONS

Our prevalence estimates of DC in white Alabama hemochromatosis probands are similar to those found in the white US population cohorts. DC risk was unrelated to the variables we studied.

Common local founder effects for Wilson's disease and hereditary hemochromatosis; mutation studies of a large family

Wilson's disease (WND) and hereditary hemochromatosis (HH) are two metal loading diseases of copper and iron, respectively, and are both recessively inherited. In central Sweden, where HH is common, 9 Wilson kindred (14 members) were identified. Aims of the study were to test whether nine WND families shared a common origin, a common mutation and if carrying HFE mutations affected their phenotype.

RESULTS

The nine families were traced through 13 generations to a common founder origin in the mid-seventeenth century. Despite identity of descent, four different ATP7B mutations appeared with homozygosity in four, with two different mutations, W779X and T977M. There were three compound heterozygotes, W779X/T977M, R1319X/H1069Q and one T977M combined with a new, previously not described mutation, probably of Finnish origin. The founder family also included 26 descendant kindred (55 members) with HH as shown by HFE mutations. This admixture coincided with a migration out of the original parish into hemochromatosis-rich localities. One WND patient had iron overload (serum ferritin 672 µg/l and raised liver enzymes), but lacked HFE mutations. In another family with serious hemochromatosis (two sons dying from bronze diabetes), the coinheritance of congenital spherocytosis was probably the cause rather than an additional effect of WND.

CONCLUSIONS

WND though a rare disease may become aggregated like HH in certain areas due to local founder effects. Despite extensive pedigree studies leading back to the local founder family, the authors were unable to find a single defining mutation of the ATP7B gene.

[Hemochromatosis--from an underdiagnosed curiosity to a common disease]

BACKGROUND

Hemochromatosis is a common disease with a good prognosis, when diagnosed early and treated appropriately. The aim of this overview is to give updated information on hemochromatosis with special focus on biochemical features, diagnosis and treatment.

MATERIAL AND METHODS

This article is based on our own experience and a review of available literature in various databases such as PubMed and Medline.

RESULTS

Hereditary hemochromatosis is an autosomal recessive disease characterized by iron overload due to increased intestinal iron uptake over many years. Hemochromatosis is often discovered through coincidental detection of high levels of transferrin and/or ferritin. The early symptoms are asthenia and joint pain. About 85 % of patients with hereditary hemochromatosis are homozygote for the C282Y mutation in the HFE: gene, but the majority of homozygotes remain asymptomatic. With ferritin levels > 500 microg/, both hereditary hemochromatosis and iron overload (of unknown cause) are treated with blood-letting.

INTERPRETATION

The pathogenesis is not fully elucidated but recent reports indicate that the protein hepcidin (produced in the liver) plays a key role in the development of hemochromatosis. Iron overload may also be secondary to other diseases such as thalassemia and other conditions requiring multiple long-term blood transfusions. The goal is to maintain ferritin values at approximately 20 - 50 microg/L.

HLA haplotype map of river valley populations with hemochromatosis traced through five centuries in Central Sweden

BACKGROUND

The hemochromatosis mutation, C282Y of the HFE gene, seems to have originated from a single event which once occurred in a person living in the north west of Europe carrying human leukocyte antigen (HLA)-A3-B7. In descendants of this ancestor also other haplotypes appear probably caused by local recombinations and founder effects. The background of these associations is unknown. Isolated river valley populations may be fruitful for the mapping of genetic disorders such as hemochromatosis. In this study, we try to test this hypothesis in a study from central Sweden where the haplotyope A1-B8 was common.

METHODS

HLA haplotypes and HFE mutations were studied in hemochromatosis patients with present or past parental origin in a sparsely populated (1/km(2)) rural district (n = 8366 in the year of 2005), in central Sweden. Pedigrees were constructed from the Swedish church book registry. Extended haplotypes were studied to evaluate origin of recombinations.

RESULTS

There were 87 original probands, 36 females and 51 males identified during 30 yr, of whom 86% carried C282Y/C282Y and 14% C282Y/H63D. Of 32 different HLA haplotypes A1-B8 was the most common (34%), followed by A3-B7 (16%), both in strong linkage disequilibrium with controls, (P < 0.001). Twenty-nine different families with A1-B8 had a common founder origin 15 generations ago in small bottleneck populations of the late 16th century. A second A1-B8 founder born 1655 was of Norwegian origin. Most of the A3 carriers (n = 26) had a common founder origin 16 generations ago in an even smaller nearby river valley. A fourth founder family carrying HLA-A2 seems to have originated from a recombination along the descendant lines from the A3 ancestor supported by extended haplotype studies. A1-haplotypes with alleles at the B locus different from B8 had a similar recombination origin as HLA-A2 alleles and a common founder origin 11 generations ago. The intergenerational time interval averaged 35.5 +/- 7.9 yr in men and 31.9 +/- 5.9 in females.

CONCLUSIONS

River valley populations may contain HLA haplotypes reflecting their demographic history. This study has demonstrated that the resistance against recombinations between HLA-A and HFE make HLA haplotypes excellent markers for population movements. Founder effects and genetic drift from bottleneck populations (surviving the plague?) may explain the commonness of the mutation in central Scandinavia. The intergenerational time difference >30 yr was greater than expected and means that the age of the original mutation may be underestimated.