Hemochromatosis gene variants in three different ethnic populations: effects of admixture for screening programs

Hereditary hemochromatosis beyond hyperferritinemia: Clinical and laboratory investigation of the patient's profile submitted to phlebotomy in two reference centers in southern Brazil

Hereditary Hemochromatosis is a disorder characterized by iron deposition in several organs and hyperferritinemia. The most studied variants are linked to the HFE gene. In Brazil, surveys that characterize this population are scarce, with no sampling in the state of Rio Grande do Sul. Our objective is to carry out a data collection focusing on the profile of this population and the influence of the most frequently HFE variants. Two centers were enrolled: Hospital de Clínicas de Porto Alegre and Hospital São Vicente de Paulo. Patients with hyperferritinemia and undergoing phlebotomy were invited. Clinical data were collected, including HFE investigation. Among the descriptive data, the allele frequency of the C282Y variant (0.252) stands out, which differs from the national scenario. Systemic arterial hypertension was the most cited comorbidity. Differences between centers were observed, highlighting higher frequency of H63D cases in HSVP (p<0.01). Genotypes were stratified according to deleterious effect of C282Y variant. Higher transferrin saturation and number of phlebotomies were observed in the C282Y/C282Y cases (p<0.001). Positive family history for hyperferritinemia was more prevalent in compound heterozygotes (p<0.01). The results presented confirm the importance of encouraging such studies and reiterate the need for greater attention to this population.

Analysis of HFE genes C282Y, H63D, and S65D in patients with hyperferritinemia from northeastern Brazil

BACKGROUND

Hereditary hemochromatosis (HH) is a genetic disease caused by the high absorption and deposition of iron in several organs. This accumulation results in several clinical complications such as cirrhosis, arthritis, cardiopathies, diabetes, sexual disorders, and skin darkening. The H63D and C282Y mutations are well defined in the HH etiology. The objective of this article is identification of the H63D and C282Y mutations in the HFE protein gene and the frequency assessment of these mutations in patients with persistent increase of serum ferritin in patients from Natal City from state of Rio Grande do Norte, located in northeastern Brazil.

RESULTS

Of the 299 patients studied for C282Y and H63D, 48.49% showed absence of mutation and 51.51% showed some sort of mutation: heterozygous C282Y mutation in 4.35% patients, homozygous C282Y mutation in 2.67% patients, heterozygous H63D mutation in 31.44% patients, homozygous H63D mutation in 8.03% patients, and heterozygous for the mutation in both genes (C282Y/H63D) in 5.02% patients. The S65C mutation was studied in 112 patients and heterozygous mutation (S65D/WT) in 2.67% of patients and double mutation (H63D/S65C) in 1.78% of patients were observed.

CONCLUSION

Due to the high prevalence of hemochromatosis, its genetic diagnosis has become a challenge, especially in the high-risk group.

Precipitating factors of porphyria cutanea tarda in Brazil with emphasis on hemochromatosis gene (HFE) mutations. Study of 60 patients

BACKGROUND

Porphyria cutanea tarda is the most common form of porphyria, characterized by the decreased activity of the uroporphyrinogen decarboxylase enzyme. Several reports associated HFE gene mutations of hereditary hemochromatosis with porphyria cutanea tarda worldwide, although up to date only one study has been conducted in Brazil.

OBJECTIVES

Investigation of porphyria cutanea tarda association with C282Y and H63D mutations in the HFE gene. Identification of precipitating factors (hepatitis C, HIV, alcoholism and estrogen) and their link with HFE mutations.

METHODS

An ambispective study of 60 patients with PCT was conducted during the period from 2003 to 2012. Serological tests for hepatitis C and HIV were performed and histories of alcohol abuse and estrogen intake were investigated. HFE mutations were identified with real-time PCR.

RESULTS

Porphyria cutanea tarda predominated in males and alcohol abuse was the main precipitating factor. Estrogen intake was the sole precipitating factor present in 25% of female patients. Hepatitis C was present in 41.7%. All HIV-positive patients (15.3%) had a history of alcohol abuse. Allele frequency for HFE mutations, i.e., C282Y (p = 0.0001) and H63D (p = 0.0004), were significantly higher in porphyria cutanea tarda patients, compared to control group. HFE mutations had no association with the other precipitating factors.

CONCLUSIONS

Alcohol abuse, hepatitis C and estrogen intake are prevalent precipitating factors in our porphyria cutanea tarda population; however, hemochromatosis in itself can also contribute to the outbreak of porphyria cutanea tarda, which makes the research for HFE mutations necessary in these patients

Global prostate cancer incidence and the migration, settlement, and admixture history of the Northern Europeans

The most salient feature of prostate cancer is its striking ethnic disparity. High incidences of the disease are documented in two ethnic groups: descendents of the Northern Europeans and African Americans. Other groups, including native Africans, are much less susceptible to the disease. Given that many risk factors may contribute to carcinogenesis, an etiological cause for the ethnic disparity remains to be defined. By analyzing the global prostate cancer incidence data, we found that distribution of prostate cancer incidence coincides with the migration and settlement history of Northern Europeans. The incidences in other ethnic groups correlate to the settlement history and extent of admixture of the Europeans. This study suggests that prostate cancer has been spread by the transmission of a genetic susceptibility that resides in the Northern European genome.

Hemojuvelin and hepcidin genes sequencing in Brazilian patients with primary iron overload

BACKGROUND

most hereditary hemochromatosis (HH) patients are homozygous for the p.C282Y mutation in the HFE gene. Some studies reported that HH phenotypic expression could be modulated by genetic factors such as HJV and HAMP gene mutations.

AIMS

the aims of this study were to identify HJV and HAMP mutations and to analyze their impact on HH phenotype in non-p.C282Y homozygous individuals.

METHODS

Twenty-four Brazilian patients with primary iron overload and non-p.C282Y homozygous genotype (transferrin saturation >50% in women and >60% in men and absence of secondary causes) were selected. Subsequent bidirectional sequencing of the HJV and HAMP exons was performed.

RESULTS

sequencing revealed a substitution in heterozygosis, c.929C > G, which corresponds to p.A310G polymorphism in HJV exon 4 (rs7540883). In the same gene, in another individual, an IVS1-36C > G intronic variant was detected in heterozygosis. In the HAMP gene, an IVS3 + 42G > A intronic variant was identified. There were six (25.0%) patients carrying a heterozygous genotype for the HFE p.C282Y and nine (37.5%) patients carrying a heterozygous genotype for the HFE p.H63D.

CONCLUSION

HJV p.A310G polymorphism and two intronic variants were found, but none of these alterations were associated with digenic inheritance with the HFE gene. Our data indicate that HJV and HAMP functional mutations are not frequent in these patients.

HFE gene mutations in patients with primary iron overload: is there a significant improvement in molecular diagnosis yield with HFE sequencing?

Rare HFE variants have been shown to be associated with hereditary hemochromatosis (HH), an iron overload disease. The low frequency of the HFE p.C282Y mutation in HH-affected Brazilian patients may suggest that other HFE-related mutations may also be implicated in the pathogenesis of HH in this population. The main aim was to screen for new HFE mutations in Brazilian individuals with primary iron overload and to investigate their relationship with HH. Fifty Brazilian patients with primary iron overload (transferrin saturation>50% in females and 60% in males) were selected. Subsequent bidirectional sequencing for each HFE exon was performed. The effect of HFE mutations on protein structure were analyzed by molecular dynamics simulation and free binding energy calculations. p.C282Y in homozygosis or in heterozygosis with p.H63D were the most frequent genotypic combinations associated with HH in our sample population (present in 17 individuals, 34%). Thirty-six (72.0%) out of the 50 individuals presented at least one HFE mutation. The most frequent genotype associated with HH was the homozygous p.C282Y mutation (n=11, 22.0%). One novel mutation (p.V256I) was indentified in heterozygosis with the p.H63D mutation. In silico modeling analysis of protein behavior indicated that the p.V256I mutation does not reduce the binding affinity between HFE and β2-microglobulin (β2M) in the same way the p.C282Y mutation does compared with the native HFE protein. In conclusion, screening of HFE through direct sequencing, as compared to p.C282Y/p.H63D genotyping, was not able to increase the molecular diagnosis yield of HH. The novel p.V256I mutation could not be implicated in the molecular basis of the HH phenotype, although its role cannot be completely excluded in HH-phenotype development. Our molecular modeling analysis can help in the analysis of novel, previously undescribed, HFE mutations.

Analysis of HFE and non-HFE gene mutations in Brazilian patients with hemochromatosis

BACKGROUND

Approximately one-half of Brazilian patients with hereditary hemochromatosis (HH) are neither homozygous for the C282Y mutation nor compound heterozygous for the H63D and C282Y mutations that are associated with HH in Caucasians. Other mutations have been described in the HFE gene as well as in genes involved in iron metabolism, such as transferrin receptor 2 (TfR2) and ferroportin 1 (SCL40A1).

AIMS

To evaluate the role of HFE, TfR2 and SCL40A1 mutations in Brazilian subjects with HH.

PATIENTS AND METHODS

Nineteen male subjects (median age 42 [range: 20-72] years) with HH were evaluated using the Haemochromatosis StripAssay A. This assay is capable of detecting twelve HFE mutations, which are V53M, V59M, H63D, H63H, S65C, Q127H, P160delC, E168Q, E168X, W169X, C282Y and Q283, four TfR2 mutations, which are E60X, M172K, Y250X, AVAQ594-597del, and two SCL40A1 mutations, which are N144H and V162del.

RESULTS

In our cohort, nine (47%) patients were homozygous for the C282Y mutation, two (11%) were heterozygous for the H63D mutation, and one each (5%) was either heterozygous for C282Y or compound heterozygous for C282Y and H63D. No other mutations in the HFE, TfR2 or SCL40A1 genes were observed in the studied patients.

CONCLUSIONS

One-third of Brazilian subjects with the classical phenotype of HH do not carry HFE or other mutations that are currently associated with the disease in Caucasians. This observation suggests a role for other yet unknown mutations in the aforementioned genes or in other genes involved in iron homeostasis in the pathogenesis of HH in Brazil.

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.

Hemochromatosis gene variants in patients with cardiomyopathy

Iron depletion was suggested to be protective against the development of ischemic heart disease. Population studies have led to conflicting results, and such an association has not been addressed in patients with heart failure due to cardiomyopathy. We studied the distribution of hemochromatosis-related mutations in 319 patients with heart failure due to cardiomyopathy of different etiologies. The genotypic distribution showed a significantly higher prevalence of heterozygotes for the C282Y mutation in patients with ischemic cardiomyopathy than in patients with cardiomyopathy of nonischemic etiologies (p = 0.0036). The frequency of the D63 mutation was not significantly different between ischemic versus nonischemic groups. In multiple logistic regression models adjusted for age, sex, ethnicity, and different degrees of disease progression, there was a strong and significant association of the C282Y mutation with ischemic cardiomyopathy compared with the nonischemic group (odds ratio 6.64, 95% confidence interval 1.71 to 25.73, after adjustment). In our sample, genetic variation in the HFE gene was associated with ischemic cardiomyopathy. Such association merits further study regarding its value as a prognostic marker in patients with ischemic heart disease.