Long-Read Sequencing Identifies the First Retrotransposon Insertion and Resolves Structural Variants Causing Antithrombin Deficiency

The identification of inherited antithrombin deficiency (ATD) is critical to prevent potentially life-threatening thrombotic events. Causal variants in SERPINC1 are identified for up to 70% of cases, the majority being single-nucleotide variants and indels. The detection and characterization of structural variants (SVs) in ATD remain challenging due to the high number of repetitive elements in SERPINC1. Here, we performed long-read whole-genome sequencing on 10 familial and 9 singleton cases with type I ATD proven by functional and antigen assays, who were selected from a cohort of 340 patients with this rare disorder because genetic analyses were either negative, ambiguous, or not fully characterized. We developed an analysis workflow to identify disease-associated SVs. This approach resolved, independently of its size or type, all eight SVs detected by multiple ligation-dependent probe amplification, and identified for the first time a complex rearrangement previously misclassified as a deletion. Remarkably, we identified the mechanism explaining ATD in 2 out of 11 cases with previous unknown defect: the insertion of a novel 2.4 kb SINE-VNTR-Alu retroelement, which was characterized by de novo assembly and verified by specific polymerase chain reaction amplification and sequencing in the probands and affected relatives. The nucleotide-level resolution achieved for all SVs allowed breakpoint analysis, which revealed repetitive elements and microhomologies supporting a common replication-based mechanism for all the SVs. Our study underscores the utility of long-read sequencing technology as a complementary method to identify, characterize, and unveil the molecular mechanism of disease-causing SVs involved in ATD, and enlarges the catalogue of genetic disorders caused by retrotransposon insertions.

IX international curse of continuing formation in haemophilia and other congenital coagulopathies. The role of the Laboratory in coagulation disorders. Diagnosis of von Willebrand disease

Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (VWF). This protein far from simplicity constitutes a very complex molecular model, remaining unravelled yet many aspects of it, even though the VWF gene (VWF) was cloned already in 1985 and the structure of VWF well defined. VWD diagnosis is difficult to achieve in a significant proportion of patients due to both disease heterogeneity and limitations in existing test processes. The cornerstone of diagnosis relies on interpretation of VWF test results, the presence of clinical manifestations of bleeding, especially mucocutaneous, and (in most cases) a positive family history. However, even with a significant bleeding history, a family history may not be positive due to factors of incomplete penetrance and variable expressivity that affect genetic changes. The laboratory diagnosis of VWD can be difficult, as the disease is heterogeneous and an array of assays is required to describe the phenotype. Basic classification of quantitative (type 1 and 3) and qualitative (type 2 variants) VWD requires determination of VWF antigenic (VWF:Ag) levels and assaying of VWF ristocetin cofactor (VWF:RCo) activity. The latter is required for identifying and subtyping VWD, but the assay is poorly standardized. For that reason, novel VWF activity assays have been developed awaiting more extensive comparison data between different methodologies and requiring validation on larger patient series. The qualitative type 2 VWF deficiency can be further divided into four different subtypes (A, B, M and N) using specific assays that measure other activities or the size distribution of VWF multimers. However, frequently, it may be difficult to correctly classify the VWD phenotype, and genetic analysis is through mutation identification may provide a tool to clarify the disorder.

Type 2N VWD: Conclusions from the Spanish PCM-EVW-ES project

INTRODUCTION

Type 2N von Willebrand disease (VWD) is characterized by a decreased affinity of von Willebrand factor (VWF) for factor VIII (FVIII). Abnormal binding of FVIII to VWF (VWF:FVIIIB), results in low FVIII plasma levels, which can lead to a misdiagnosis of mild haemophilia A. Accurate diagnosis of type 2N VWD is essential for appropriate genetic counselling and therapy. This disease can be distinguished from haemophilia A by in vitro assays (measurement VWF:FVIIIB activity) and/or genetic analysis.

AIM

To identify the current challenges in the diagnosis and treatment of this type of VWD and provide an in-depth description of the phenotypes and mutations identified.

RESULTS

Twenty-eight patients had at least one type 2N mutation, and 13 of these had a type 2N mutation combined with other variations. Three type 2N mutations were detected: p.Arg816Trp, p.Arg854Gln, and p.Arg763Ser. Two of these are the most frequently described mutations worldwide. This mutational spectrum differs from the broad spectrum seen in neighbouring France, where at least eight distinct 2N mutations have been found. In the PCM-EVW-ES cohort, 11 asymptomatic type 2N carriers with borderline FVIII plasma levels would probably have been excluded if the evaluation had been based on clinical and laboratory data only. Likewise, three patients with a severe phenotype would have been classified as homozygous for a 2N mutation if only the phenotype study had been performed.

CONCLUSION

The high detection yield and affordability of next-generation sequencing support the use of this technology as a first-line diagnostic tool in this setting.

Adherence to prophylaxis in adult patients with severe haemophilia A

INTRODUCTION

Adherence is a cornerstone of factor VIII prophylactic treatment. Information regarding the factors with potential influence on adherence is limited, particularly in adult patients.

AIM

To assess adherence in adult patients with severe haemophilia A receiving prophylactic treatment in a real-life setting, and investigate the factors influencing adherence.

METHODS

Observational, prospective study including adult patients receiving factor VIII therapy in 15 Spanish centres. Patients recorded infusion doses on a logbook and answered various questionnaires to assess their health beliefs. Adherence rate was the percentage of infused doses over the prescribed ones. Self-perceived adherence was assessed using the VERITAS-Pro questionnaire, the psychometric properties of which were validated in the Spanish population. The relationship between adherence rate and treatment, clinical and demographic characteristics, health beliefs and perceived self-efficacy was investigated.

RESULTS

A total of 66 patients were followed up for 12 months. Mean adherence rate at the end of follow-up was 82.5%. Most of the study patients (n = 53, 80.3%) showed a moderate-to-high adherence rate (>70%). The VERITAS-Pro revealed a high perception of adherence. Multivariate analyses to predict treatment adherence identified the knee as a target joint and longer treatment duration as variables with significant (negative) influence on adherence. Adherence rate was not influenced by the patient's health beliefs or perceived self-efficacy.

CONCLUSION

Most adult patients receiving factor VIII prophylactic treatment in Spain have moderate-to-high treatment adherence. Treatment duration and the knee as a target joint are factors with a moderate negative influence on treatment adherence.

Prophylaxis therapy with bypassing agents in patients with haemophilia A and inhibitors undergoing surgery: A cost analysis in Spain

Objectives

This study estimated the cost of prophylaxis with activated prothrombin complex concentrate (aPCC) and recombinant activated factor VIIa (rFVIIa) in surgical patients with haemophilia A and inhibitors in Spain.

Methods

A decision‐analytic model was developed to estimate the cost to the Spanish National Health System of providing haemostatic coverage in this haemophilia population, with age distribution and average weight derived from the literature, and the annual number of surgeries (0.33 per patient) from local data. Drug costs were calculated from official ex‐factory prices with a 7.5% mandatory deduction and recommended dosing regimens.

Results

The estimated average costs per patient were €10 100.73 (aPCC) and €14 265.89 (rFVIIa) for dental extraction, €24 043.88 (aPCC) and €62 301.08 (rFVIIa) for minor surgery and €126 595.81 (aPCC) and €347 731.09 (rFVIIa) for major surgery. Assuming an estimated 23 annual surgeries in this population (N = 69), distributed as 19% dental extraction, 50% minor surgery and 31% major surgery, the total annual cost of prophylaxis was €1 209 682.35 with aPCC and €3 221 929.28 with rFVIIa.

Conclusions

aPCC costs were 62.5% lower than rFVIIa. Assuming potential clinical equivalence, aPCC is a potentially cost‐saving option for surgical patients with haemophilia A and inhibitors.

Unraveling the Influence of Common von Willebrand factor variants on von Willebrand Disease Phenotype: An Exploratory Study on the Molecular and Clinical Profile of von Willebrand Disease in Spain Cohort

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the "Molecular and Clinical Profile of von Willebrand Disease in Spain project." To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

Update on Molecular Testing in von Willebrand Disease

Diagnosis of von Willebrand disease (VWD) depends on personal and family history of bleeding and confirmatory laboratory testing. Currently available phenotypic tests for VWD contain potential sources for error that may distort results. Despite an exponential growth of information about the von Willebrand factor gene (VWF), the role of molecular diagnosis in VWD is still controversial. Due to the complexity and high cost of conventional molecular analyses, some investigators have recommended limiting this approach to distinguish suspected type 2N VWD from hemophilia A, type 2B from platelet-type VWD, and the exploration of type 3 VWD. New genetic methodologies and approaches are becoming available, but there is still some reluctance for their implementation in VWD diagnosis. This article discusses the pros and cons of molecular testing in VWD considering the experience obtained through the multicenter project “Molecular and Clinical Profile of VWD in Spain (PCM-EVW-ES).”

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Prevalence, Follow-Up and Clinical Significance of the Anticardiolipin Antibodies in Normal Subjects

To date very few studies that analyze the prevalence of anticardiolipin antibodies (ACA) in healthy subjects have been reported. No data based on a systematic analysis of normal subjects with positive ACA is available. The aim of the present study was to evaluate the prevalance of ACA, its clinical significance and relationship to the lupus anticoagulant (LA) and other autoimmune parameters in an apparently healthy population. 552 normal blood donors from a blood bank were randomly selected. ACA positive donors who consented were monitored over a period of twelve months and tested every three months. ACA (IgG and IgM isotypes) were quantitated by enzyme linked immunoassay (ELISA). The prevalance for IgG ACA in our donor population was estimated to be 6.5%, and 9.4% for IgM ACA, which is similar to the one previously reported for IgG and slightly higher for IgM. It is worth noting that in our study ACA positive donors exhibited a progressive negativization. Eight donors with IgG ACA and seven with IgM ACA remained positive for nine months. Five donors with IgG ACA and four with IgM ACA had family history of thromboembolic disease. One donor with IgG ACA and two with IgM ACA had had unexplained miscarriages in the past. We did not find any relationship between ACA and LA, nor between ACA positivity and the clinical and laboratory data studied. Pseudopositivity for lues was not found. No thrombotic event occurred in donors that were positive for ACA during the 12-month follow-up.

Abnormal Structure of von Willebrand Factor in Myeloproliferative Syndrome Is Associated to Either Thrombotic or Bleeding Diathesis

The multimeric and subunit patterns of plasma von Willebrand factor (vWF) were analyzed in eight patients with myeloproliferative syndrome (MS) in order to investigate the possible existence of heterogeneity in the “in vivo” proteolytic cleavage of the protein, previously observed in this entity. Six patients lacked large vWF multimers, five of them having normal bleeding times (BT) and clinically documented episodes of thrombotic origin, whereas one patient had long BT and bleeding symptoms. Seven patients showed a relative increase in the 176 kDa subunit fragment while the 189 kDa polypeptide was increased in only one. In addition, another patient (and prior to any therapy) showed the presence of a new fragment of approximately 95 kDa which disappeared after Busulfan therapy. The collection of blood from these patients with proteinase inhibitors did not correct the abnormalities.

The infusion of DDAVP to two patients with abnormal vWF was accompanied by: the appearance of larger vWF multimers which disappeared rapidly from plasma; an increase in the relative proportion of the satellite bands of each multimer and a further increase of the 176 kDa fragment. These data point to some heterogeneity in the vWF abnormality present in MS which may be related in part to a variable degree of proteolysis of vWF occurring “in vivo” rather than “in vitro”, and which may be associated to either a thrombotic or a bleeding diathesis. They also suggest that despite the presence of abnormal, already proteolyzed vWF, DDAVP-enhanced proteolysis occurs in MS to a similar extent to what is described in normal individuals.

Role of multimeric analysis of von Willebrand factor (VWF) in von Willebrand disease (VWD) diagnosis: Lessons from the PCM-EVW-ES Spanish project

The multimeric analysis (MA) of plasma von Willebrand factor (VWF) evaluates structural integrity and helps in the diagnosis of von Willebrand disease (VWD). This assay is a matter of controversy, being considered by some investigators cumbersome and only slightly informative. The centralised study ‘Molecular and Clinical Profile of von Willebrand Disease in Spain (PCM-EVW-ES)’ has been carried out by including the phenotypic assessment and the genetic analysis by next generation sequencing (NGS) of the VWF gene (VWF). The aim of the present study was to evaluate the role of MA to the diagnosis of these patients and their potential discrepancies. Two hundred and seventy out of 480 patients centrally diagnosed with VWD had normal multimers, 168 had abnormal multimers and 42 a total absence of multimers. VWF MA was of great significance in the diagnosis of 83 patients (17.3%), it was also of help in the diagnosis achieved in 365 additional patients (76%) and was not informative in 32 cases (6.7%). With regard to discrepancies, 110 out of 480 (23%) patients centrally diagnosed with VWD presented some kind of discordance between VWF:RCo/VWF:Ag and/or VWF:CB/VWF:Ag ratios, multimeric study and/or genetic results. The VWF MA was key in the presence of novel mutations as well as in cases with phenotypic discrepancies. A comparison between the contribution of MA and VWF:CB showed a clearly higher contribution of the former in the diagnostic process. These data seem to reinforce the relevance of the VWF MA in VWD diagnosis, despite all its limitations.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): comprehensive genetic analysis by next-generation sequencing of 480 patients

Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.

Diagnosis of inherited von Willebrand disease: comparison of two methodologies and analysis of the discrepancies

Diagnostics of von Willebrand disease (VWD) includes assessment of factor VIII (FVIII) coagulant activity, von Willebrand factor (VWF) antigen (VWF:Ag) and VWF ristocetin cofactor activity (VWF:RCo), and more specific tests as multimeric and genetic analyses are necessary for the correct VWD classification. The ACL AcuStar analyzer introduces chemiluminescence (CL) technology in detection of VWD with automated VWF:Ag and VWF:RCo assays. Compare VWF:Ag-ELISA and VWF:RCo by aggregometry conventional assays with new CL VWF:Ag-IL and VWF:RCo-IL assays, investigate the ability to make accurate VWD diagnosis and concordance with multimeric and genetic analyses. 146 patients with congenital VWD (51 Type 1; 34 Type 2A; 16 Type 2B; 31 Type 2M; 5 Type 2N; 9 Type 3) and 30 healthy normal subjects were included. A comparison was made between CL and conventional methods. Diagnostic evaluation included: VWF:RCo/VWF:Ag ratio, multimeric distribution (sodium dodecyl sulfate [SDS]-agarose gel) of VWF and genetic analysis in 110 of 146 patients. CL and conventional methods revealed good correlation. Kappa test agreement diagnosis was >0.8. CL diagnostic sensitivity was 100% and specificity 97%. Multimeric and genetic analysis were of help in clarifying 13 discrepancies of diagnosis between methods, of which six discrepancies were explained by lack of conventional methods′ sensibility. CL methodology can detect VWD and discriminate between type 1, 3 and variant forms and offers an automated, faster, sensitive and less cumbersome method when compared to conventional assays, in particular VWF:RCo by aggregometry. In some cases, even with all phenotype and genetic analyses, discrepancies exist in the classification of VWD.

Pharmacogenetics of acenocoumarol in patients with extreme dose requirements

SUMMARY BACKGROUND

There is currently intense debate as to whether pharmacogenetic algorithms for estimating the initial dose of coumarins provide a more accurate dose than the fixed-dose approach. Recently, it has been suggested that the greatest benefit of pharmacogenetic algorithms is observed in patients with extreme dose requirements.

OBJECTIVES

To identify clinical and genetic factors that better characterize patients who need extreme acenocoumarol doses for steady anticoagulation state.

PATIENTS/METHODS

We reviewed 9538 patients with a steady acenocoumarol dose from three Spanish hospitals, selecting 83 who took or= 30.00 mg week(-1) (p95). We also selected patients matched by gender and age taking 13.50-14.00 mg week(-1) (p50). We genotyped VKORC1 (rs9923231), CALU (rs1043550), GGCX (rs699664), CYP2C9 (rs1799853; rs1057910), CYP4F2 (rs2108622) and F7 (rs5742910) single-nucleotide polymorphisms (SNPs).

RESULTS

Comparison between p5 and p95 revealed five parameters with significant differences: body surface area (BSA) (P = 0.006), age, VKORC1, CYP2C9 and CYP4F2 genotypes (all P < 0.001). First VKORC1, and second, CYP2C9 SNPs played a strong effect by determining extreme doses, particularly in p95. Only one out of 203 p95 had the VKORC1 A-1639A genotype, but this subject was CYP2C9*1/*1. In contrast, nine out of 83 p5 carried the VKORC1 G-1639G genotype, although six of them were CYP2C9*3 homozygotes and another two were heterozygotes. Surprisingly, CYP4F2 V433M SNP displayed prevalences that suggest that its influence might only be evident when patients are treated with high doses.

CONCLUSION

Two clinical data, age and BSA, and three SNPs in the VKORC1, CYP2C9 and CYP4F2 genes strongly predict outlier patients treated with acenocoumarol.

Von Willebrand factor/factor VIII concentrates in the treatment of von Willebrand disease

Therapy for von Willebrand disease (VWD) aims to restore the hemostatic function conferred by von Willebrand factor (VWF), which facilitates platelet adhesion and aggregation, and serves to increase potentially low coagulation factor VIII (FVIII) in plasma. In patients unresponsive to desmopressin (DDAVP), the preferred treatment is with plasma-derived VWF-containing FVIII concentrates. Only a few of the available VWF/FVIII concentrates have been licensed for use in VWD based on prospective studies. The efficacy of VWF/FVIII concentrates depends on the content and quality of VWF and FVIII. Several studies have demonstrated the variability of the VWF contents, as well as the differences in the VWF multimer patterns (including the high molecular weight VWF multimers that are most effective in restoring hemostasis), among these concentrates. Treating physicians should be aware of these disparities and the potential clinical implications for patients with different VWD subtypes. Dosing has traditionally been calculated based on the FVIII content of the products, although dosing based on VWF functional activity [e.g., VWF ristocetin cofactor activity (VWF:RCo)] addresses the primary protein deficiency in VWD patients. Several clinical studies have demonstrated the efficacy of concentrates dosed according to VWF:RCo. Dosing is generally consistent across VWD subtypes, although patients with severe phenotypes or undergoing major procedures may require more infusions or longer treatment duration. Other considerations for the use of VWF-containing concentrates include laboratory monitoring of efficacy and safety issues such as thrombosis risk and thromboprophylaxis.

von Willebrand disease R1374C: type 2A or 2M? A challenge to the revised classification. High frequency in the northwest of Spain (Galicia)

Patients initially diagnosed with type 1 von Willebrand disease (VWD) have been reclassified as type 2 after a more exhaustive analysis in several studies. Our study's objectives were (1) to reanalyze patients that were previously diagnosed as type 1 to achieve a more accurate diagnosis and (2) to compare the von Willebrand factor (VWF) ristocetin cofactor assay (VWF:RCo) and the VWF collagen binding assay (VWF:CB) in order to evaluate the possibility of replacing the former assay with the latter in the diagnosis of VWD. Twenty-one patients from two large unrelated families and 104 normal controls were studied. VWF:Ag, VWF:RCo, FVIII coagulant activity (FVIII:C), bleeding time (BT), PFA(100), and multimeric analysis of VWF were tested. Genetic analysis by sequencing exon 28 on the VWF gene was also carried out. Patients presented lower levels of VWF:Ag and VWF:RCo, a dissociation between VWF:RCo/VWF:Ag, and the presence of all sizes of multimers in plasma VWF. The results for VWF:CB varied depending on the type of collagen used. The genetic analysis showed that the mutation R1374C is responsible for type 2M VWD. A high frequency of the R1374C mutation is observed in northwestern Spain (Galicia). Some types of 2M VWD are misdiagnosed as type 1 VWD. The VWF:CB (with type I collagen) assay was unable to discriminate defective platelet binding of the R1374C VWF. This confirms that VWF:CB cannot substitute for VWF:RCo, and both should be tested when diagnosing VWD.

Type 2B von Willebrand's disease due to Val1316Met mutation. Heterogeneity in the same sibship

An analysis was conducted in four members of the same family, two of whom had a history of severe bleeding associated with type 2B von Willebrand's disease (VWD) which, although found to be due to the same mutation, nevertheless exhibited different phenotype patterns in the two subjects involved. Von Willebrand's factor (VWF) multimers were assayed with high- and low-resolution sodium dodecyl sulfate (SDS) agarose gels. The patients were studied before and after intravenous administration of desmopressin (DDAVP) at doses of 0.4 microg/kg body weight. Automatic sequencing techniques were used to analyze VWF gene exon 28. The propositus presented with mild basal thrombocytopenia with ristocetin-induced platelet aggregation (RIPA) at low concentrations of ristocetin. He had a very prolonged bleeding time (BT), and his plasma VWF was found to be lacking in large and intermediate multimers. Thrombocytopenia was observed to intensify transiently after the administration of DDAVP. The propositus' mother, in contrast, presented reduced RIPA while in a basal state, with only partial loss of the high molecular weight VWF multimers. Although she had a very prolonged BT, her platelet count was borderline. Transient correction of BT and a decrease in the platelet count were observed after administration of DDAVP and RIPA was observed at low concentrations of ristocetin. Exon 28 sequencing revealed a G4196A-->Val1316Met mutation in both patients. No other abnormality was detected within this exon. Val1316Met has been reported in type 2B VWD. In conclusion, in the family presented here, the phenotype pattern in one patient was typical of type 2B VWD, whereas the pattern in his mother was closer to type 2A VWD. After administration of DDAVP, however, a type 2B phenotype could be clearly attributed to both, indicating that this drug can be a useful tool for elucidating ambiguous phenotypes.

Antibodies to factor VIII in plasma of patients with hemophilia A and normal subjects

Non-neutralizing factor VIII (FVIII) antibodies (FVIII-Ab) in hemophilia A may be associated with an abnormal clinical response to FVIII concentrates. Patients with FVIII inhibitors may develop noncoagulation FVIII-Ab after the induction of immunotolerance. Natural FVIII-Ab may be detected in the plasma of some healthy subjects. The aim of this study was to analyze the presence of FVIII-Ab in the plasma of 53 normal blood donors and 124 patients with hemophilia A (18 patients had a previous history of FVIII inhibitor, but only 12 had inhibitor at the moment this study was performed). FVIIII inhibitor was measured using the Bethesda method. FVIII-Ab were analyzed by a specific ELISA assay using purified FVIII from a monoclonal concentrate and a standard plasma containing 26 Bethesda units (BU) of FVIII inhibitor. Purified FVIII was used to coat wells of a microtiter plate and was incubated with dilutions of plasma to be tested. Bound human IgG FVIII-Ab were detected by incubation with polyclonal sheep anti.human IgG alkaline phosphatase conjugate, and the OD405 was quantitated. A linear fit was obtained (by plotting FVIII-Ab positivity [OD 405nm] versus BU titer) when serial dilutions of this standard inhibitor plasma, containing titers of 0.5 BU or higher, were used. Four different levels of FVIII-Ab positivity [OD 405nm] were distinguished in this assay: Negative levels (-) were obtained with dilutions of the standard inhibitor containing < 0.5 BU. Mild levels (+) were obtained with dilutions of 0.5-5 BU. Moderate levels (+2) were obtained for dilutions ranging from 5-25 BU. Maximum positivity (+3) was obtained for dilutions of titers > 25 BU. FVIII-Ab positivity was detected in eight of the normal subjects (15%): three were found to be moderately positive (+2) and five mildly positive (+). No inhibitory activity was detectable when whole plasma was used. All the hemophilic patients with a presence of FVIII inhibitor at the time of the study were found to be positive for FVIII-Ab. In addition, the level of positivity correlated with the corresponding BU. Four of the six patients who had a history of inhibitory were negative and two positive. Twenty additional patients (16.12%) in whom no inhibitory activity was detected were found to be positive for FVIII-Ab: 16 + and four +2. The mean age of patients with FVII-Ab positivity was significantly higher than that of patients of the FVIII-Ab negative group (p < 0.005). In conclusion, FVIII-Ab positivity in patients with hemophilia A was 17.7% higher than the level of positivity detected by an inhibitory assay. We propose that this method for FVIII-Ab analysis could be used for patients with hemophilia A, at least to complement the functional inhibitor assay. FVIII recovery or half-life should be assessed in patients who test positive for FVIII-Ab and who show no evidence of inhibitor.

Prevalence, follow-up and clinical significance of the anticardiolipin antibodies in normal subjects

To date very few studies that analyze the prevalence of anticardiolipin antibodies (ACA) in healthy subjects have been reported. No data based on a systematic analysis of normal subjects with positive ACA is available. The aim of the present study was to evaluate the prevalence of ACA; its clinical significance and relationship to the lupus anticoagulant (LA) and other autoimmune parameters in an apparently healthy population. 552 normal blood donors from a blood bank were randomly selected. ACA positive donors who consented were monitored over a period of twelve months and tested every three months. ACA (IgG and IgM isotypes) were quantitated by enzyme linked immunoassay (ELISA). The prevalence for IgG ACA in our donor population was estimated to be 6.5%, and 9.4% for IgM ACA, which is similar to the one previously reported for IgG and slightly higher for IgM. It is worth noting that in our study ACA positive donors exhibited a progressive negativization. Eight donors with IgG ACA and seven with IgM ACA remained positive for nine months. Five donors with IgG ACA and four with IgM ACA had family history of thromboembolic disease. One donor with IgG ACA and two with IgM ACA had had unexplained miscarriages in the past. We did not find any relationship between ACA and LA, nor between ACA positivity and the clinical and laboratory data studied. Pseudopositivity for lues was not found. No thrombotic event occurred in donors that were positive for ACA during the 12-month follow-up.

Further evidence for recessive inheritance of von Willebrand disease with abnormal binding of von Willebrand factor to factor VIII

A new family with a bleeding diathesis and FVIII deficiency secondary to abnormal binding of von Willebrand factor (vWF) to factor VIII (FVIII) is described. Two propositi of this family, an 18-year-old male and a 33-year-old female, both with a history of epistaxis, bruising, bleeding from the gums, epistaxis, hemarthrosis, and hematoma, were analyzed. Also additional members of the same family with no bleeding history were also studied. The propositi showed normal vWF activities, low FVIII activity; one of them had been diagnosed as having hemophilia A and the other was a hemophilia A carrier. Both showed a very poor response to treatment with FVIII concentrates and desmopressin (DDAVP) but a good clinical response to cryoprecipitate. APTT was prolonged and no inhibitory activity was noticeable in their plasmas. Thirty-five units per kilogram body weight of Hemofil M was infused to both propositi and FVIII reached basal level within 60 minutes of the infusion. No FVIII response at all was observed in the female after intravenous DDAVP administration. However, the male who received the infusion of 35 U/kg body weight of Humate-P achieved a normal FVIII level that was maintained for 12 hours. Multimeric analysis of vWF was normal in all the members studied. Von Willebrand factor domain for FVIII binding was assayed in the two propositi and in six other members of the same family by using a non-isotopic and sensitive method, a modification of the one previously described, using the Hemofil M concentrate as exogenous FVIII. The data obtained showed that both propositi had similar binding to that observed by using plasma of a patient with severe von Willebrand disease. Furthermore, five siblings had a decreased binding of vWF to FVIII, when compared with plasma from normal individuals or patients with hemophilia A. We also observed that, for screening purpose, the ratio of bound FVIII/immobilized vWF (at saturation of the anti-vWF and offering of 1 U/ml of exogenous FVIII) distinguished two levels of abnormality (normal range 0.70-1.15, propositi 0.004-0.007, and remaining members affected 0.25-0.42). The most probable explanation is that the propositi are homozygous or double heterozygous, the other five siblings affected being heterozygous for a recessive vWF defect. This more accessible assay presented here may be of help in routine analysis for diagnosing this type of von Willebrand disease, which has important implications for therapy and genetic counseling.

High levels of plasma FVIII and vWF in the toxic epidemic syndrome patients

Factor VIII and von Willebrand factor proteins were evaluated in 115 patients having the chronic phase of the Toxic Epidemic Syndrome (TES), a new multisystemic disease probably caused by the ingestion of denatured rapeseed oil, and in 50 control volunteers. Higher circulating levels of factor VIII procoagulant activity (VIII:C) (158 +/- 58.4 U/dl), von Willebrand factor antigen (vWF:Ag) (166.1 +/- 55.5 U/dl) and von Willebrand factor ristocetin cofactor activity (vWF:RCo) (178.7 +/- 55.2 U/dl) were seen in TES patients (p less than 0.001, TES patients versus control subjects, for each parameter). The increased levels of vWF:Ag and vWF:RCo observed in TES patients correlated with the scleroderma like lesion of the skin, with the sicca syndrome and with Raynaud's phenomenon (p less than 0.01), but not with other clinical manifestations. The multimeric analysis of vWF in 92% of the TES patients was similar to that found in normal plasma, but in the remaining 8% a very slight increase of larger vWF multimers in plasma were observed. The raised levels of vWF found in TES patients in the chronic phase may reflect an "in vivo" vascular injury.

High Levels of Plasma FVIII and vWF in the Toxic Epidemic Syndrome Patients

Factor VIII and von Willebrand factor proteins were evaluated in 115 patients having the chronic phase of the Toxic Epidemic Syndrome (TES), a new multisystemic disease probably caused by the ingestion of denatured rapeseed oil, and in 50 control volunteers. Higher circulating levels of factor VIII procoagulant activity (VIII :C) (158 ± 58.4 U/dl), von Willebrand factor antigen (vWF: Ag) (166.1 ± 55.5 U/dl) and von Willebrand factor ristocetin cofactor activity (vWF:RCo) (178.7 ± 55.2 U/dl) were seen in TES patients (p < 0.001, TES patients versus control subjects, for each parameter). The increased levels of vWF:Ag and vWF:RCo observed in TES patients correlated with the scleroderma like lesion of the skin, with the sicca syndrome and with Raynaud's phenomenon (p < 0.01), but not with other clinical manifestations. The multimeric analysis of vWF in 92% of the TES patients was similar to that found in normal plasma, but in the remaining 8% a very slight increase of larger vWF multimers in plasma were observed. The raised levels of vWF found in TES patients in the chronic phase may reflect an “in vivo” vascular injury.

Further specificity characterization of von Willebrand factor inhibitors developed in two patients with severe von Willebrand disease

Circulating inhibitors against von Willebrand factor (vWF) that show the properties of heterologous IgG antibodies have been described in a few patients with severe von Willebrand disease (vWD). The present study provides further characterization of inhibitors from two patients with severe vWD. Inhibitors in both, like polyclonal rabbit antibody, detected all sizes of multimers and the complex structure of each multimer from platelets and plasma of normal individuals as well as from plasma of patients with IIA, IIB, and IIC vWD. Both inhibitors and the rabbit antibody reacted mainly with the intact 225-Kd vWF subunit and the 189-H and 140-Kd fragments in contrast to monoclonal antibodies specific for vWF fragments that detected a higher relative proportion of 176-Kd fragment. Furthermore, all these antibodies recognized fragment III, although one inhibitor and rabbit polyclonal antibody reacted poorly and the other inhibitor did not react at all with reduced fragment II of vWF digested with Staphylococcus aureus V-8 protease. These data suggest that although human inhibitors from severe vWD patients may behave, to some extent, as polyclonal heterologous antibodies against native vWF, the former show striking differences in their target specificity as well as a much broader specificity than that described for human factor VIII inhibitors.

Type IIB von Willebrand's disease associated with a complex thrombocytopenic thrombocytopathy

A familial bleeding disorder characterized by an association of Type IIB von Willebrand's disease (vWD) with a complex thrombocytopenic thrombocytopathy is described in two patients from the same generation. Findings typical of type IIB vWD included enhanced ristocetin-induced binding of patient von Willebrand factor (vWF) to platelets of patients and normal individuals in association with the absence of larger multimers from plasma. Abnormalities in platelet function included deficient platelet aggregation to ADP, collagen, epinephrine, and arachidonic acid; and defective release of 14C-serotonin, vWF, and platelet factor 4 (PF4) in response to thrombin, collagen, or ADP. Platelet factor 4 and platelet vWF were decreased when measured per mg of total platelet protein. In addition, the binding of normal vWF to patient platelets stimulated with thrombin was decreased. Platelet size was increased with a very heterogeneous distribution width. Electron microscopic evaluation showed giant platelets with dense and alpha bodies present. The platelet count was borderline or slightly decreased in the resting state and declined to frankly thrombocytopenic levels at the time of acute bleeding episodes; this state was associated with the presence of platelet aggregates in blood smears.

Abnormal structure of von Willebrand factor in myeloproliferative syndrome is associated to either thrombotic or bleeding diathesis

The multimeric and subunit patterns of plasma von Willebrand factor (vWF) were analyzed in eight patients with myeloproliferative syndrome (MS) in order to investigate the possible existence of heterogeneity in the "in vivo" proteolytic cleavage of the protein, previously observed in this entity. Six patients lacked large vWF multimers, five of them having normal bleeding times (BT) and clinically documented episodes of thrombotic origin, whereas one patient had long BT and bleeding symptoms. Seven patients showed a relative increase in the 176 kDa subunit fragment while the 189 kDa polypeptide was increased in only one. In addition, another patient (and prior to any therapy) showed the presence of a new fragment of approximately 95 kDa which disappeared after Busulfan therapy. The collection of blood from these patients with proteinase inhibitors did not correct the abnormalities. The infusion of DDAVP to two patients with abnormal vWF was accompanied by: the appearance of larger vWF multimers which disappeared rapidly from plasma; an increase in the relative proportion of the satellite bands of each multimer and a further increase of the 176 kDa fragment. These data point to some heterogeneity in the vWF abnormality present in MS which may be related in part to a variable degree of proteolysis of vWF occurring "in vivo" rather than "in vitro", and which may be associated to either a thrombotic or a bleeding diathesis. They also suggest that despite the presence of abnormal, already proteolyzed vWF, DDAVP-enhanced proteolysis occurs in MS to a similar extent to what is described in normal individuals.

Assessment of multimeric structure and ristocetin-induced binding to platelets of von Willebrand factor present in cryoprecipitate and different factor VIII concentrates

The multimeric structure of von Willebrand factor (vWF) and its ristocetin-induced binding to platelets, using a simple and very sensitive radiomonoclonal antibody-labeled vWF method, was compared in normal plasma, single-donor cryoprecipitate (CP) and five different antihemophilic factor (AHF) concentrates. All the AHF showed a lack of larger vWF multimers, an abnormal 'triplet' pattern, and much lower vWF binding to platelets than that of plasma or CP, vWF being the lowest for those with a lesser proportion of larger vWF multimers. These results suggest that the combination of vWF multimeric analysis and the radiomonoclonal-labeled vWF method may be very useful in the assessment of AHF preparations.

Unique multimeric pattern of von Willebrand factor in a patient with a benign monoclonal gammopathy

A 60-yr-old woman had had a bleeding disorder for the last 13 yr, with laboratory features of monoclonal gammopathy and von Willebrand's disease (vWD). There was no evidence of family vWD. She had a prolonged bleeding time, low levels of factor VIII/von Willebrand factor activities and decreased ristocetin-induced platelet agglutination. Platelet von Willebrand factor (vWF) was normal. Plasma vWF showed a unique multimeric pattern with absence of larger and intermediate multimers and a disproportionate increase of the fastest moving multimer with normal satellite bands, thus differing from previously described types of vWF. No evidence for inhibitor, non neutralizing antibody or proteolytic activity against vWF was found in her plasma or IgG fraction. DDAVP response was very poor. We suggest that this patient had a unique, probably acquired, vWD. Nevertheless the possibility of its being a new subtype of congenital vWD associated with an unrelated monoclonal gammopathy cannot be ruled out.