Mutation analysis of factor VIII in Korean patients with severe hemophilia A

The prevalence and risk factors of inhibitor development of FVIII in previously treated patients with hemophilia A

Background

Risk factors for the development of inhibitors in previously untreated patients (PUPs) have been reported; this is not the case in previously treated patients (PTPs) owing to fewer studies. Risk factors may differ for the development of PTP versus PUP inhibitors. We aimed to identify risk factors for PTP inhibitor development.

Methods

Participants were patients at a hemophilia treatment center in Korea with current or past history of factor VIII or factor IX alloantibodies. Observed inhibitors were classified as PUP or PTP inhibitors based on the cumulative number of exposure days. We compared the type and severity of hemophilia, mutation type, and family history of inhibitor between PUPs and PTPs. Events within 3 months before the first inhibitor detection, such as change of the factor concentrate used, short-term high exposure or continuous infusion of factor concentrate, history of surgery, infection, diagnosis of cancer, use of immunosuppressive or immunomodulator agents, and vaccination were compared between PUPs and PTPs.

Results

We observed 5 PUP inhibitors and 5 PTP inhibitors in 115 patients with hemophilia A. Events that might be related to the development of inhibitors within 3 months prior to the first inhibitor detection were observed in all 5 PTPs. On the contrary, no such events were observed in any PUPs. The observed events included a change in the factor concentrate used, subsequent chemotherapy, and short-term high exposure to factor concentrates for controlling hemorrhage and surgeries.

Conclusion

Our results suggest a greater role of nongenetic factors in PTP inhibitor development.

F8 inversions of introns 22 and 1 confer a moderate risk of inhibitors in Mexican patients with severe hemophilia A. Concordance analysis and literature review

Intron-22 (Inv22) and intron-1 (Inv1) inversions account for approximately one half of all severe cases of hemophilia A (SHA) worldwide. Inhibitor development against exogenous factor VIII (FVIII) represents a major complication in HA. The causative F8 mutation is considered the most decisive factor conditioning inhibitor development. We aimed to investigate prevalence of Inv22 and Inv1 mutations, and its association as risk factors for developing inhibitors to FVIII. We investigated Inv22 and Inv1 in 255 SHA Mexican patients from 193 unrelated families using the inverse shifting-polymerase chain reaction (IS-PCR). We analyzed the association between inversions and inhibitor development via logistic regression introducing as covariates the populations, the inversions, F8-haplotypes and the age of patients at enrollment. Inv22 was found in 91/193 (47.2%: 38.9% exhibited Inv22-1 and 8.3% Inv22-2), and Inv1 in 2/193 (1.0%) independent families. Absolute inhibitor prevalence (IP) for Inv22 in unrelated patients was 15% (10-19). The cohorts and age of patients were independent predictors of inhibitor risk, but not inversions or haplotypes. Inversions presence in our population was associated to a moderate risk of developing inhibitors. Inv1 was found for the first time in two Mexican families. A relevant genetic component was observed by the strong concordance among brother-pairs.

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.

Heterogeneous lengths of copy number mutations in human coagulopathy revealed by genome-wide high-density SNP array

BACKGROUND

The recent advent of genome-wide molecular platforms has facilitated our understanding of the human genome and disease, particularly copy number aberrations. We performed genome-wide single nucleotide polymorphism-array in hereditary coagulopathy to delineate the extent of copy number mutations and to assess its diagnostic utility.

DESIGN AND METHODS

The study subjects were 17 patients with hereditary coagulopathy from copy number mutations in coagulation genes detected by multiple ligation-dependent probe amplification. Eleven had hemophilia (7 hemophilia A and 4 hemophilia B) and 6 had thrombophilia (4 protein S deficiency and 2 antithrombin deficiency). Single nucleotide polymorphism-array experiments were performed using Affymetrix Genome-Wide Human SNP arrays 6.0.

RESULTS

Copy number mutations were identified by single nucleotide polymorphism-array in 9 patients, which ranged in length from 51 Kb to 6,288 Kb harboring 2 to ~160 genes. Single nucleotide polymorphism-array showed a neutral copy number status in 8 patients including 7 with either a single-exon copy number mutation or duplication mutations of PROS1.

CONCLUSIONS

This study revealed unexpectedly heterogeneous lengths of copy number mutations underlying human coagulopathy. Single nucleotide polymorphism-array had limitations in detecting copy number mutations involving a single exon or those of a gene with homologous sequences such as a pseudogene.