Genetic analysis of haemophilia A in Taiwan

Serum TNF-α Level as a Possible Predictor of Inhibitor Levels in Severe Hemophilia A

BACKGROUND

The development of factor VIII (FVIII) inhibitor in patients with hemophilia A (PWHA) is a great challenge for hemophilia care. Both genetic and environmental factors led to complications in PWHA. The development of inhibitory antibodies is usually induced by the immune response. Tumor necrosis factor α (TNF-α), one of the cytokines, might contribute to its polymorphism. In this study, we investigated the clinical factors, level of serum TNF-α, and polymorphism of c.-308G > A TNF - α gene in inhibitor development in severe PWHA.

METHODS

A cross-sectional study was conducted among all PWHA in West Java province. The clinical parameters, FVIII, FVIII inhibitor, and serum TNF-α level were assessed. The genotyping of -380G > A TNF-α gene polymorphism was performed using polymerase chain reaction and Sanger sequencing.

RESULTS

Among the 258 PWHA, 216 (83.7%) were identified as severe PWHA. The FVIII inhibitor was identified in 90/216 (41.6%) of severe PWHA, consisting of 45 high-titer inhibitors (HTI) and 45 low-titer inhibitors (LTI). There was a significant correlation between serum TNF-α level and the development of HTI (p = 0.043). The cutoff point of serum TNF-α level, which can be used to differentiate between HTI and LTI, was 11.45 pg/mL. The frequency of FVIII replacement therapy was significant only in HTI of severe PWHA regarding serum TNF-α level (p = 0.028). There is no correlation between polymorphisms of -380G > A TNF-α gene and inhibitor development (p = 0.645).

CONCLUSIONS

The prevalence of FVIII inhibitor in severe PWHA in West Java, Indonesia, was 41.6%. The frequency of replacement therapy is a risk factor for inhibitor development. Serum TNF-α level might be used to differentiate between high and low inhibitor levels in severe hemophilia A, and this might support decision making regarding treatment options for inhibitor in severe hemophilia A.

Factor VIII inhibitor development in Egyptian hemophilia patients: does intron 22 inversion mutation play a role?

Background

Hemophilia A (HA) is an X-linked recessive bleeding disorder characterized by qualitative and quantitative deficiency of factor VIII (FVIII). The development of inhibitor antibodies against FVIII is the most challenging complication of treatment. Mutations in the FVIII gene is one of the genetic factors that leads to development of FVIII inhibitors especially intron 22 inversion (Inv22).

Objectives

This study was carried out to assess the frequency of Inv22 of FVIII gene in Egyptian patients with hemophilia A and its role as a risk factor for developing inhibitors.

Patients and methods

Seventy-two patients with severe HA and 48 patients with moderate HA were enrolled in the current study. All patients were treated on demand with either plasma-derived factor VIII or recombinant factor VIII concentrates. Genotyping of FVIII Inv22 was performed by LD-PCR while the presence and magnitude of inhibitor activity in blood was determined by the Bethesda assay.

Results

Around 23% of all hemophilia cases had positive Inv22. Intron 22 inversion mutation was detected in 6 and 33% of patients with moderate and severe HA respectively. Twenty-one cases (18%) of all hemophilic patients developed inhibitors. Thirty-7% of patients with Inv22 had inhibitor in their blood, almost all, but one, had severe HA. The risk of an inhibitor development during replacement therapy was four folds higher among Inv22 positive cases as compared with mutation negative peers (OR 4.3, 95% CI 1.6–11.9, P = 0.003).

Conclusions

The prevalence of Inv22 of F VIII in Egyptian hemophiliacs is nearly like that of other population. This mutation was more frequently detected among severe hemophilic patients as compared with moderately affected peers. The presence of Inv22 mutation significantly predispose to FVIII inhibitor development.

Factor 8 Gene Mutation Spectrum of 270 Patients with Hemophilia A: Identification of 36 Novel Mutations

Objective

Hemophilia A (HA) is the most severe X-linked inherited bleeding disorder caused by hemizygous mutations in the factor 8 (F8) gene. The aim of this study is to determine the mutation spectrum of the F8 gene in a large HA cohort from Turkey, and then to establish a phenotype-genotype correlation.

Materials and Methods

All HA cases (270 patients) analyzed molecularly in the Ege University Pediatric Genetics Molecular Laboratory between March 2017 and March 2018 were included in this study. To identify intron 22 inversion (Inv22), intron 1 inversion (Inv1), small deletion/insertions, and point mutations, molecular analyses of F8 were performed using a sequential application of molecular techniques.

Results

The mutation detection success rate was 95.2%. Positive Inv22 was found in 106 patients (39.3%), Inv1 was found in 4 patients (1.5%), and 106 different disease-causing sequence variants were identified in 137 patients (50.6%). In 10 patients (3.7%), amplification failures involving one or more exonic regions, considered to be large intragenic deletions, were identified. Of 106 different F8 mutations, 36 were novel. The relationship between F8 genotype and inhibitor development was considered significant.

Conclusion

A high mutation detection rate was achieved via the broad molecular techniques applied in this study, including 36 novel mutations. With regard to mutation types, mutation distribution and their impact on clinical severity and inhibitor development were found to be similar to those previously reported in other hemophilia population studies.

Deep intronic variant c.5999-277G>A of F8 gene may be a hot spot mutation for mild hemophilia A patients without mutation in exonic DNA

BACKGROUND

In 10%-18% of mild-type hemophilia A (HA) patients, mutations cannot be found by routine DNA analysis.

OBJECTIVE

We aimed to identify the genetic defects by mRNA analysis of F8 gene in mild HA patients without mutation in exonic DNA.

PATIENTS AND METHODS

From 2006 to 2016, we identified F8 exon mutations in 39 of 49 mild HA patients using routine genetic testing. We then evaluated the 10 remaining patients from six unrelated families without exonic DNA mutation by performing cDNA sequence analysis.

RESULTS

Nine of the 10 (90%) patients were confirmed to have F8 gene mutation. Eight patients from four unrelated families were notably found to have presence of an aberrant 675-bp fragment. Sequencing of this fragment showed that there were two separate new alternative splicing exons of 35 bp and 55 bp within intron 18, which formed a 90-bp insertion between exon 18 and exon 19 (E18ins90bpE19) in the mRNA. Based on direct sequencing, this alternative splicing transcript appears to have resulted from deep intronic variant c.5999-277G>A of intron 18.

CONCLUSIONS

Our study suggests that deep intronic variant of c.5999-277G>A may be a hot spot mutation for mild hemophilia patients without mutation in exonic DNA.

Spectrum of Molecular Defects in 216 Chinese Families With Hemophilia A: Identification of Noninversion Mutation Hot Spots and 42 Novel Mutations

Hemophilia A (HA) is an X-linked bleeding disorder caused by heterogeneous mutations in the factor VIII gene ( F8). Our aim is to identify the causative mutations in a large HA cohort from China. We studied 216 unrelated HA families. Molecular analyses of F8 were performed using a combination of molecular techniques, including polymerase chain reaction, direct sequencing, and multiplex ligation-dependent probe amplification. The deleterious consequences of the unreported missense mutations were evaluated using various bioinformatics approaches. Causative mutations in F8 were identified in 209 families, intron 22 inversion (Inv22) was identified in 89 severe families, and intron 1 inversion (Inv1) was positive in 5 severe families; 95 mutations were detected among 115 noninversion families, of which 42 were novel, including 29 null variations and 13 missense mutations for which causality was demonstrated via bioinformatics. Among the 53 previously reported mutations, more nonsense (5 of 9) and missense (10 of 26) mutation sites were found to occur at Arginine (Arg) sites and multiple small deletions/insertions (5 of 10) located within the poly-A runs of the B domain. The majority of these sequence variants frequently recurred in the database. The odds ratios for the likelihood of developing inhibitors significantly increased in the presence of nonsense mutation. Our F8 defect spectrum was heterogeneous. Small deletions/insertions in the poly-A runs of the B domain and nonsense and missense mutations at Arg sites were identified as mutation hot spots. Nonsense mutation increased the risk of developing inhibitors.

Violating the theory of single gene-single disorder: inhibitor development in hemophilia

Hemophilia is clinically and genetically heterogeneous blood disorder with several known gene defects accounting for the diversity of disease phenotype and inhibitor production. Although increasing number of causative mutations have been reported, not much is known regarding the root cause of inhibitor development against infused blood clotting factors, which represents a major challenge in the treatment of disease. The variations in the severity and frequency of bleeding in hemophiliacs with same molecular defect, indicates the role of modifier genes in the pathogenesis of disease. Herein, we aim to review and summarise the literature over the past decade, to gain insight into what is critical for the development of inhibitors in hemophilia. Aside from potential mutations in factor VIII and IX, polymorphisms in various genes such as human leukocyte antigen-I (HLA-I), HLA-II, tumor necrosis factor-alpha, interleukin-10 and cytotoxic T-lymphocyte associated antigen-4, also tends to contribute to the development of inhibitors. Violating the theory of single gene-single disorder, new research indicates that inhibitor arise from a complex interplay of multiple genetic, immunological and environmental factors. With the revolutionary advances in whole genome sequencing, we propose a detailed genome wide study to identify the spectrum of genetic markers involved in the development of inhibitors for better diagnostics and therapeutics.

Prevalence, incidence, and factor concentrate usage trends of hemophiliacs in Taiwan

PURPOSE

Hemophilia A and B (HA, HB) are the most common X-linked inherited bleeding disorders. The introduction of factor concentrates has allowed for control of the lifelong chronic disease. However, no studies have been published regarding the epidemiology of hemophilia in Taiwan. Our aim was to determine the prevalence, incidence, and mortality rate, as well as trends in the use of factor concentrates, in individuals with hemophilia in Taiwan.

MATERIALS AND METHODS

A retrospective study was conducted using the National Health Insurance Research Database between 1997 and 2007.

RESULTS

We identified 988 males with hemophilia (HA : HB ratio=5.4 : 1). The mean prevalence per 100000 males was 6.7 ± 0.1 for HA and 1.2 ± 0.1 for HB. The estimated mean annual incidence per live male birth was 1 in 10752 for HA and 1 in 47619 for HB. Standardized mortality ratios for males with hemophilia (all severities) or severe hemophilia were 1.3- and 2.1-fold higher than that of the general male population, respectively. Mean factor VIII (FVIII) and factor IX (FIX) usage was 1.5003 ± 0.4029 and 0.3126 ± 0.0904 international units (IUs) per capita, respectively. Mean FVIII and FIX usage per patient with hemophilia (all severities) or severe hemophilia was 44027 ± 11532 and 72341 ± 17298, respectively, and 49407 ± 13015 and 74369 ± 18411 IUs per person with HA or HB, respectively.

CONCLUSION

Our data revealed epidemiologic and factor concentrate usage trends in males with hemophilia in Taiwan, highlighting a need for improvements in the mandatory National Health Insurance registry. A better- designed, patient-centered registry system would enable more detailed patient information collection and analysis, improving subsequent care.