Most Factor VIII B Domain Missense Mutations Are Unlikely to Be Causative Mutations for Hemophilia A: Implications for Factor VIII Genetic Analysis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 513-513
Author(s):  
Kyoichi Ogata ◽  
Steven W. Pipe
Keyword(s):  
Amino Acid ◽  
Factor Viii ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Causative Mutation ◽  
Factor V ◽  
Missense Mutations ◽  
Severe Hemophilia ◽  
Single Chain

Abstract Hemophilia A results from the quantitative or qualitative deficiency of coagulation factor VIII (FVIII). FVIII is synthesized as a single-chain polypeptide of approximately 280 kDa with the domain structure A1-A2-B-A3-C1-C2. Whereas the A and C domains exhibit ~40% amino acid identity to each other and to the A and C domains of coagulation factor V, the B domain is not homologous to any known protein and is dispensable for FVIII cofactor activity. Missense mutations in the FVIII B domain have been described in patients with variable phenotypes of hemophilia A. According to the NCBI SNPs (single nucleotide polymorphism) database, 22 SNPs are reported within FVIII, 11 of which occur within the B domain. FVIII B domain variant D1241E has been reported as a missense mutation associated with mild or severe hemophilia A, yet this mutation is also present in the NCBI SNPs database. We hypothesize that D1241E and most other reported B domain missense mutations are not the causative mutation for hemophilia A in these patients but represent SNPs or otherwise non-pathologic mutations. To investigate this, we analyzed 7 B domain missense mutations that were previously found in hemophilia A patients (T751S, V993L, H1047Y, D1241E, T1353A, P1641L and S1669L). Comparative analysis showed that the amino acids at these positions are not conserved in all species and in some cases, the amino acid substitution reported in hemophilia patients is represented in the native sequence in other species. Analysis with PolyPhen Software showed that only H1047Y mutation was considered as “possibly damaging”, while the others were considered as “benign”. To investigate this further, we constructed seven plasmid vectors containing these B domain missense mutations. The synthesis and secretion of FVIII wild-type (WT) and these seven mutants were compared after transient DNA transfection into COS-1 monkey cells in vitro. Analysis of the FVIII clotting activity and antigen levels in the conditioned medium demonstrated that all mutants had FVIII activity and antigen levels similar to FVIII WT. Further, FVIII WT, H1047Y and D1241E mutants were introduced into a FVIII exon 16 knock-out mouse model of hemophilia A by hydrodynamic tailvein injection in vivo. The mouse plasma was analyzed at 24 hrs for activity and antigen expression. Mutants H1047Y and D1241E expressed at 211 mU/mL and 224 mU/mL activity with FVIII antigen levels of 97 ng/mL and 118 ng/mL, respectively, similar to FVIII WT. These results suggested that H1047Y and D1241E mutants did not lead to impairments in secretion or functional activity. We conclude that most missense mutations within the FVIII B domain would be unlikely to lead to severe hemophilia A and that the majority of such missense mutations represent polymorphisms or non-pathologic mutations. Investigators should search for additional potentially causative mutations elsewhere within the FVIII gene when B domain missense mutations are identified.

scholarly journals An In Vitro Analysis of the Combination of Hemophilia A and Factor VLEIDEN

Blood ◽  
1997 ◽  
Vol 90 (8) ◽  
pp. 3067-3072 ◽  
Author(s):  
Cornelis van ‘t Veer ◽  
Neal J. Golden ◽  
Michael Kalafatis ◽  
Paolo Simioni ◽  
Rogier M. Bertina ◽  
...  
Keyword(s):  
Factor Viii ◽  
Tissue Factor ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Factor Viia ◽  
Factor V ◽  
Severe Hemophilia ◽  
Factor Viii Activity ◽  
Thrombin Formation

Abstract The classification of factor VIII deficiency, generally used based on plasma levels of factor VIII, consists of severe (<1% normal factor VIII activity), moderate (1% to 4% factor VIII activity), or mild (5% to 25% factor VIII activity). A recent communication described four individuals bearing identical factor VIII mutations. This resulted in a severe bleeding disorder in two patients who carried a normal factor V gene, whereas the two patients who did not display severe hemophilia were heterozygous for the factor VLEIDEN mutation, which leads to the substitution of Arg506 → Gln mutation in the factor V molecule. Based on the factor VIII level measured using factor VIII–deficient plasma, these two patients were classified as mild/moderate hemophiliacs. We studied the condition of moderate to severe hemophilia A combined with the factor VLEIDEN mutation in vitro in a reconstituted model of the tissue factor pathway to thrombin. In the model, thrombin generation was initiated by relipidated tissue factor and factor VIIa in the presence of the coagulation factors X, IX, II, V, and VIII and the inhibitors tissue factor pathway inhibitor, antithrombin-III, and protein C. At 5 pmol/L initiating factor VIIa⋅tissue factor, a 10-fold higher peak level of thrombin formation (350 nmol/L), was observed in the system in the presence of plasma levels of factor VIII compared with reactions without factor VIII. Significant increase in thrombin formation was observed at factor VIII concentrations less than 42 pmol/L (∼6% of the normal factor VIII plasma concentration). In reactions without factor VIII, in which thrombin generation was downregulated by the addition of protein C and thrombomodulin, an increase of thrombin formation was observed with the factor VLEIDEN mutation. The level of increase in thrombin generation in the hemophilia A situation was found to be dependent on the factor VLEIDEN concentration. When the factor VLEIDEN concentration was varied from 50% to 150% of the normal plasma concentration, the increase in thrombin generation ranged from threefold to sevenfold. The data suggested that the analysis of the factor V genotype should be accompanied by a quantitative analysis of the plasma factor VLEIDEN level to understand the effect of factor VLEIDEN in hemophilia A patients. The presented data support the hypothesis that the factor VLEIDEN mutation can increase thrombin formation in severe hemophilia A.

scholarly journals Mutations of factor VIII cleavage sites in hemophilia A

Blood ◽  
1988 ◽  
Vol 72 (3) ◽  
pp. 1022-1028 ◽  
Author(s):  
J Gitschier ◽  
S Kogan ◽  
B Levinson ◽  
EG Tuddenham
Keyword(s):  
Amino Acid ◽  
Factor Viii ◽  
Cleavage Site ◽  
Hemophilia A ◽  
Activated Protein C ◽  
Gene Mutations ◽  
Coagulation Factor ◽  
Cleavage Sites ◽  
Severe Hemophilia ◽  
Thrombin Activation

Abstract Hemophilia A is caused by a defect in coagulation factor VIII, a protein that undergoes extensive proteolysis during its activation and inactivation. To determine whether some cases of hemophilia are caused by mutations in important cleavage sites, we screened patient DNA samples for mutations in these sites by a two-step process. Regions of interest were amplified from genomic DNA by repeated rounds of primer- directed DNA synthesis. The amplified DNAs were then screened for mutations by discriminant hybridization using oligonucleotide probes. Two cleavage site mutations were found in a survey of 215 patients. A nonsense mutation in the activated protein C cleavage site at amino acid 336 was discovered in a patient with severe hemophilia. In another severely affected patient, a mis-sense mutation results in a substitution of cysteine for arginine in the thrombin activation site at amino acid 1689. This defect is associated with no detectable factor VIII activity, but with normal levels of factor VIII antigen. The severe hemophilia in this patient was sporadic; analysis of the mother suggested that the mutation originated in her gametes or during her embryogenesis. The results demonstrate that this approach can be used to identify factor VIII gene mutations in regions of the molecule known to be important for function.

scholarly journals Mutations of factor VIII cleavage sites in hemophilia A

Blood ◽  
1988 ◽  
Vol 72 (3) ◽  
pp. 1022-1028
Author(s):  
J Gitschier ◽  
S Kogan ◽  
B Levinson ◽  
EG Tuddenham
Keyword(s):  
Amino Acid ◽  
Factor Viii ◽  
Cleavage Site ◽  
Hemophilia A ◽  
Activated Protein C ◽  
Gene Mutations ◽  
Coagulation Factor ◽  
Cleavage Sites ◽  
Severe Hemophilia ◽  
Thrombin Activation

Hemophilia A is caused by a defect in coagulation factor VIII, a protein that undergoes extensive proteolysis during its activation and inactivation. To determine whether some cases of hemophilia are caused by mutations in important cleavage sites, we screened patient DNA samples for mutations in these sites by a two-step process. Regions of interest were amplified from genomic DNA by repeated rounds of primer- directed DNA synthesis. The amplified DNAs were then screened for mutations by discriminant hybridization using oligonucleotide probes. Two cleavage site mutations were found in a survey of 215 patients. A nonsense mutation in the activated protein C cleavage site at amino acid 336 was discovered in a patient with severe hemophilia. In another severely affected patient, a mis-sense mutation results in a substitution of cysteine for arginine in the thrombin activation site at amino acid 1689. This defect is associated with no detectable factor VIII activity, but with normal levels of factor VIII antigen. The severe hemophilia in this patient was sporadic; analysis of the mother suggested that the mutation originated in her gametes or during her embryogenesis. The results demonstrate that this approach can be used to identify factor VIII gene mutations in regions of the molecule known to be important for function.

Animal Testing of Retroviral-Mediated Gene Therapy for Factor VIII Deficiency

1999 ◽  
Vol 82 (08) ◽  
pp. 555-561 ◽  
Author(s):  
Douglas Jolly ◽  
Judith Greengard
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
Joint Damage ◽  
Coagulation Factor ◽  
The United States ◽  
Severe Hemophilia ◽  
Factor Viii Gene ◽  
Bleeding Episodes

IntroductionHemophilia A results from the plasma deficiency of factor VIII, a gene carried on the X chromosome. Bleeding results from a lack of coagulation factor VIII, a large and complex protein that circulates in complex with its carrier, von Willebrand factor (vWF).1 Severe hemophilia A (<1% of normal circulating levels) is associated with a high degree of mortality, due to spontaneous and trauma-induced, life-threatening and crippling bleeding episodes.2 Current treatment in the United States consists of infusion of plasma-derived or recombinant factor VIII in response to bleeding episodes.3 Such treatment fails to prevent cumulative joint damage, a major cause of hemophilia-associated morbidity.4 Availability of prophylactic treatment, which would reduce the number and severity of bleeding episodes and, consequently, would limit such joint damage, is limited by cost and the problems associated with repeated venous access. Other problems are associated with frequent replacement treatment, including the dangers of transmission of blood-borne infections derived from plasma used as a source of factor VIII or tissue culture or formulation components. These dangers are reduced, but not eliminated, by current manufacturing techniques. Furthermore, approximately 1 in 5 patients with severe hemophilia treated with recombinant or plasma-derived factor VIII develop inhibitory humoral immune responses. In some cases, new inhibitors have developed, apparently in response to unnatural modifications introduced during manufacture or purification.5 Gene therapy could circumvent most of these difficulties. In theory, a single injection of a vector encoding the factor VIII gene could provide constant plasma levels of factor in the long term. However, long-term expression after gene transfer of a systemically expressed protein in higher mammals has seldom been described. In some cases, a vector that appeared promising in a rodent model has not worked well in larger animals, for example, due to a massive immune response not seen in the rodent.6 An excellent review of early efforts at factor VIII gene therapy appeared in an earlier volume of this series.7 A summary of results from various in vivo experiments is shown in Table 1. This chapter will focus on results pertaining to studies using vectors based on murine retroviruses, including our own work.

Interferon-Gamma (IFN-γ) Secretion Defect in Peripheral Blood Mononuclear Cells (PBMCs) from Severe Hemophilia A (HA) Patients Prior to Therapeutic Exposure To Factor VIII (FVIII) Concentrates.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3093-3093
Author(s):  
Joan Cox Gill ◽  
Karen Stephany ◽  
Craig Helsell
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Membrane Lipids ◽  
Coagulation Factor ◽  
Cytokine Secretion ◽  
Foreign Protein ◽  
Subject Group ◽  
Severe Hemophilia ◽  
Adult Control ◽  
Ifn Γ

Abstract The recent availability of highly purified recombinant coagulation factor concentrates to treat hemorrhages in hemophilic patients is thought to circumvent perturbations in immune function by preventing chronic intravenous exposure to multiple foreign protein antigens. We previously reported a PHA-induced IFN-γ secretion defect in severe hemophilia A patients who had been exposed exclusively to highly purified coagulation factor VIII concentrates. We now report the results of cytokine secretion in response to PHA in cultured PBMCs from severe hemophilia A patients never exposed to FVIII concentrates. PBMCs were isolated from whole blood from three severe HA patients, 3 age-matched normal boys, 3 boys with severe hemophilia B and an adult control. Cells were stained with PKH26 (Sigma), a fluorescent dye with aliphatic tails that intercalate into membrane lipids; cells were than washed and cultured in complete media in wells of microtiter plates with and without PHA. Cells were harvested at 5 days and proliferation detected by loss of membrane PKH26 staining detected by flow cytometry. Cytokines secreted into the supernatants of 48 hour and 5 day cultures were measured by ELISA assays (BD Pharmingen). PBMCs from severe HA patients proliferated normally in response to PHA but failed to secrete IFN-γ when compared to normal boys and boys with severe HB: PBMC Proliferation and Secretion of IFN-γ in Response to PHA Subject Group HA HB Normal Boys Adult Control PHA Proliferation (% unstained cells) M± 1SD 79.3 ±3.7 78.2±13.3 95.4±1.5 89.3±5.3 INF-γ Secretion (pg/mL) M± 1 SD 6.7±4.7 429.0±464 69.1±32.4 770.1±148.7 The severe HA patients did not have improvement in INF-γ secretion following therapeutic exposure to FVIII concentrates. Addition of physiologic concentrations of FVIII or FIX to cultures with or without PHA did not alter the results of proliferation or cytokine secretion regardless of the inhibitor history of the patients. (1 HA and 1 HB patient developed high responder inhibitors.) Secretion of IL-4, IL-5 and IL-10 were moderately decreased in some HA patients as well. In summary, we have confirmed an INF-γ secretion defect in PBMCs from patients with HA in spite of normal proliferation in response to PHA. The defect is not present in HB or normal age-matched control subjects and is not corrected by addition of FVIII to cultures. We conclude that the defect is not due to exposure to intravenous foreign antigens. The precise clinical significance and any possible relation to the higher risk of inhibitor development in HA will require further investigation. PBMC Proliferation and Secretion of IFN-γ in Response to PHA Subject Group HA HB Normal Boys Adult Control PHA Proliferation (% unstained cells) M± 1SD 79.3 ±3.7 78.2±13.3 95.4±1.5 89.3±5.3 INF-γ Secretion (pg/mL) M± 1 SD 6.7±4.7 429.0±464 69.1±32.4 770.1±148.7

scholarly journals Detection of Intron22 Mutations in Iraqi Female Carriers in Wasit City with Hemophilia A

2017 ◽  
pp. 13-24
Author(s):  
Maysoon Mohammed Hassan
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Gene Identification ◽  
Severe Hemophilia ◽  
Factor Viii Gene ◽  
Intron 1 ◽  
Detection Mechanisms ◽  
Female Carriers ◽  
Chromosomal Recombination

The background:One of the prevalent main concerns in the medical world is the identification of Intron22 mutations in the Factor VIII gene carried by Iraqi patient in Wasit town, in Iraq suffering Hemophilia A (classical hemophilia) which is related to a X-chromosome recessive haemorrhage afflictions as the result of a flaw in the coagulation factor VIII (FVIII). It is essentially related with F8 mutations of Intron22 in version which forms the most typical kind of mutations of blood afflictions worldwide involving half the patients suffering from severe Hemophilia A that possesses mutations, in addition to Intron 1 inversion suffered by 5% of severe Hemophilia A patients.All of the inversion mutations are suffered mainly by males,and uncommonly by females due to the intra chromosomal recombination among the homologous areas, in inversion 1 or 22, with extragenic copy posited the telomeric to the Factor VIII gene. Unfortunately, there is an absence in Iraq on researches pertaining blood affliction gene identification in persons who carries the Intron22 mutations exception in the current research.Aims of study:The objectives of the research is to to analyze through the detection mechanisms, the existence of Intron 22 mutations in the Factor VIII gene of 10 Hemophilia A Iraqi carriers cohort families. The hypothesis and anticipated result is that there will be a minimal margin of hazardous possibility for the recurrence. The hereditary F8 mutation is unknown to be present on the maternal side of the patient sufferer due to the possibilty of germline mosaics that exists within the community.

scholarly journals Characterization of Missense Mutations in Factor VIII That Lead to Abnormal N-Linked Glycosylation

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3764-3764 ◽  
Author(s):  
Wei Wei ◽  
Xiaofan Zhu ◽  
Renchi Yang ◽  
Bin Zhang
Keyword(s):  
Amino Acid ◽  
Factor Viii ◽  
Amino Acid Substitution ◽  
Hemophilia A ◽  
Consensus Sequence ◽  
The Other ◽  
Missense Mutations ◽  
Other Hand ◽  
Glycosylation Sites ◽  
A2 Domain

Abstract Most secreted proteins are glycosylated on the asparagine (N) residue with the consensus sequence N-X-S/T(X≠Proline).Coagulation factor VIII (FVIII) is heavily N-linked glycosylated with 5 consensus sites outside the B domain. However, the roles of these glycans are not well understood. Meanwhile, missense mutations which could create additional N-linked glycosylation sites have largely not been characterized in hemophilia A patients. In this study we first expressed individual domains of FVIII and determined that the A2, Cand C2 domains are efficiently secreted. The A1(N42,N239), A3 (N1810)and C1 (N2118)domains are glycosylated, whereas N582 in the A2 domain is not glycosylated. Only one hemophilia A missense mutation, S241C in the A1 domain, was found to abolish the consensus sequence for N-linked glycosylation at N239. We confirmed that the S241C mutant lost one glycan and became unstable inside cells. We also tested the other three glycosylation sites and found that elimination of the N-linked glycan at N2118 (N2118Q mutation) impaired the secretion of the C domain. This defect could not be rescued by adding another N-linked glycan (at N2062) in the C1 domain, indicating that the N2118 glycan is specifically required for the secretion of the C domain. We next searched the CHAMP F8 Mutation Database and the FVIII Variant Database and identified 19 missense mutations that potentially create an ectopic glycosylation site.These mutations are located in A1, A2, A3 and C1 domains, but none in the C2 domain. Only two mutations (I566T and M1772T) have previously been characterized.We found that all but one (I2071T) of these mutations gained an additional N-linked glycan. We further studied missense mutations in the A2 (A469T, A469S, I566T, M614T and G701S) and the C domain (W2062S, I2071T and D2131N) because these domains are secreted in cell culture. Whereas secretion of I566T, W2062S and D2131N mutants was comparable to their wild-type counterparts, secretion of other mutants decreased to 5%-30% of WT (P<0.05). Mutants that secreted into culture media nevertheless have low FVIII activity (<2%), indicating that these mutations cause cross reactive material positive hemophilia A. The consequences of additional N-linked glycan were further investigated using the A2 domain mutants, since this domain is normally unglycosylated. After treating with tunicamycin to block the N-linked glycosylation process in the endoplasmic reticulum (ER),the secretion of A2 domain with I566T andG701Smutants, which had relatively high secretion levels, decreased significantly. On the other hand, removing the additional glycan boosted the secretion of A469S and A469T, two low-secretion mutants.Tunicamycin treatment had no effect on another low secretion mutant,M614T.These results suggest that amino acid substitution in I566T andG701Smutationsis detrimental to the proper folding of the protein and the additional N-glycan plays a stabilization role. On the other hand, additional N-glycan plays a destabilization role in A469S and A469T mutations, contributing to disruption of folding in these mutants. For theM614Tmutation,the amino acid substitution alone is likely sufficient todestroy the protein folding. We also studied interactions of abnormally glycosylated mutants with ER chaperones.All the mutants with low secretion levels significantly induced expression of GRP78 to 1.5-2.0 folds(P<0.05), while mutants that maintain higher secretion levels did not affect GRP78 expression. The low secretion mutants also had increased binding to GRP78 and calreticulin, but not to calnexin.Therefore ER chaperones play a key role in the ER quality control of FVIII mutants. In conclusion, our results indicate that the effects of abnormal N-linked glycosylation on FVIII folding and secretionvary widely, from detrimental to beneficial. The impact of a particular glycan is likely determined by the location and the underlying amino acid change caused by the mutation. Disclosures No relevant conflicts of interest to declare.

Effect of the Factor V Leiden Mutation on the Clinical Expression of Severe Hemophilia A

2000 ◽  
Vol 83 (03) ◽  
pp. 387-391 ◽  
Author(s):  
I.R. Walker ◽  
J. Teitel ◽  
M.-C. Poon ◽  
B. Ritchie ◽  
J. Akabutu ◽  
...  
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Geometric Mean ◽  
Factor V Leiden ◽  
Significant Variable ◽  
Factor V ◽  
Severe Hemophilia ◽  
Factor V Leiden Mutation ◽  
Bleeding Episodes ◽  
Factor Concentrate

SummaryTo determine whether the factor V Leiden mutation is associated with decreased bleeding in individuals with severe hemophilia A, factor concentrate utilization, maximum annual number of bleeding episodes, and the prevalence of hemophilic arthropathy between carriers and non-carriers of the factor V Leiden mutation were compared. Heterozygosity for the factor V Leiden mutation was found in 6 of 137 subjects (4.4%). Carriers of the factor V Leiden mutation utilized less factor concentrate (geometric mean: 310 vs. 1185 units/kg/year) and had fewer bleeding episodes than non-carriers (proportion with 10 or fewer bleeding episodes in their worst year: 50 vs. 11%). However, the factor V Leiden mutation was not associated with the absence of arthropathy. The intron 22 inversion mutation of the factor VIII gene was tested for in a subgroup of 80 subjects, but it was not found to be a significant variable for any of the bleeding endpoints. The results of this small study are consistent with the hypothesis that the factor V Leiden mutation imparts a protective effect; however, a larger confirmatory study in which the factor VIII molecular defects can be controlled for is needed. Furthermore, most severe hemophiliacs who used fewer than 200 units/kg/year of factor concentrate or who had experienced 10 or fewer bleeding episodes per year did not carry the factor V Leiden mutation, suggesting that the proportion of severe hemophiliacs whose mild clinical course can be attributed to the factor V Leiden mutation is small.

Bioengineering of coagulation factor VIII for improved secretion

Blood ◽  
2004 ◽  
Vol 103 (9) ◽  
pp. 3412-3419 ◽  
Author(s):  
Hongzhi Z. Miao ◽  
Nongnuch Sirachainan ◽  
Lisa Palmer ◽  
Phillip Kucab ◽  
Michael A. Cunningham ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Mrna Levels ◽  
Golgi Transport ◽  
Recombinant Fviii ◽  
Therapy Strategies

Abstract Factor VIII (FVIII) functions as a cofactor within the intrinsic pathway of blood coagulation. Quantitative or qualitative deficiencies of FVIII result in the inherited bleeding disorder hemophilia A. Expression of FVIII (domain structure A1-A2-B-A3-C1-C2) in heterologous mammalian systems is 2 to 3 orders of magnitude less efficient compared with other proteins of similar size compromising recombinant FVIII production and gene therapy strategies. FVIII expression is limited by unstable mRNA, interaction with endoplasmic reticulum (ER) chaperones, and a requirement for facilitated ER to Golgi transport through interaction with the mannose-binding lectin LMAN1. Bioengineering strategies can overcome each of these limitations. B-domain-deleted (BDD)-FVIII yields higher mRNA levels, and targeted point mutations within the A1 domain reduce interaction with the ER chaperone immunoglobulin-binding protein. In order to increase ER to Golgi transport we engineered several asparagine-linked oligosaccharides within a short B-domain spacer within BDD-FVIII. A bioengineered FVIII incorporating all of these elements was secreted 15- to 25-fold more efficiently than full-length FVIII both in vitro and in vivo. FVIII bioengineered for improved secretion will significantly increase potential for success in gene therapy strategies for hemophilia A as well as improve recombinant FVIII production in cell culture manufacturing or transgenic animals. (Blood. 2004;103: 3412-3419)

Increased Plasminogen Activity Is An Independent Predictor of Bleeding in Hemophiliacs

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4516-4516
Author(s):  
Andrea Gerhardt ◽  
Melanie Pesch ◽  
Rudiger E. Scharf ◽  
Rainer B. Zotz
Keyword(s):  
Factor Viii ◽  
Independent Predictor ◽  
Coagulation Factor ◽  
Prothrombin G20210a ◽  
Factor V ◽  
Bleeding Events ◽  
Antifibrinolytic Agents ◽  
Low Levels ◽  
Mucosal Bleeding

Abstract Rationale and Objectives: Apart from the differences in factor VIII:C levels, it is difficult to explain the significant variation in bleeding events observed among individual patients with similar levels of FVIII:C and standard laboratory profiles. We hypothesize that additional dispositional (genetic) and expositional (non-genetic) factors of hemostasis may augment or attenuate the likelihood of bleeding symptoms in hemophiliacs. Patients and Methods: To test this hypothesis, we studied 61 patients diagnosed with hemophilia A. The following laboratory parameters were examined in multivariate analysis using a case-only analysis: genotyping for a2C807T, HPA-1 of aIIbb3, factor V G1691A, prothrombin G20210A; coagulation factor activity/antigen of fibrinogen, factor II, V, VII, VIII, IX, X, XI, XII, XIII, vWF; in-vitro bleeding time (PFA-100 closure times), and plasminogen. Results: After adjustment for age, low levels of factor VIII (p=0.0296) and increased levels of plasminogen (p=0.0415), and collagen/ADP closure times (PFA-100) (p=0.04) could be identified as independent predictors of mucosal bleeding. 10% higher activity of plasminogen increased the bleeding risk 10.4 fold. For joint bleeding low levels of fibrinogen (p=0.003) and longer collagen/epinephrine closure times (PFA-100) could be identified as bleeding predictors. Conclusion: Apart from low levels of factor VIII, increased activity of plasminogen is an independent predictor of mucosal bleeding in hemophiliacs. In consequence, it will be of importance to examine whether the critical subgroup of patients with increased plasminogen levels and mucosal bleeding can benefit from prevention with specific antifibrinolytic agents.

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