Fibrinogen Aalpha Thr312Ala polymorphism is associated with chronic thromboembolic pulmonary hypertension.

Although chronic thromboembolic pulmonary hypertension (CTEPH) is characterised by the persistence of organised thrombus, few pro-thrombotic risk factors have been identified in subjects with the disease. The aim of the present study was to compare the prevalence of eight functionally relevant haemostatic polymorphisms between CTEPH subjects and healthy controls. Genomic DNA was isolated from 214 CTEPH subjects and 200 healthy controls, and analysed for Factor V Leiden, prothrombin guanine (G) to adenine (A) substitution at nucleotide 20210 (20210G>A), plasminogen activator inhibitor-1 4G/5G, tissue plasminogen activator 7351 cytosine (C)>thymidine (T), Factor XIII 100G>T, fibrinogen Aalpha substitution of threonine with alanine at position 312 (Thr312Ala), fibrinogen Bbeta substitution of arginine with lysine at position 448 (Arg448Lys) and fibrinogen Bbeta 455G>A polymorphisms. A significant difference was demonstrated in fibrinogen Aalpha Thr312Ala genotype and allele frequencies between CTEPH subjects and controls. The presence of the alanine allele significantly increased the risk of CTEPH. The fibrinogen Aalpha alanine 312 allele alters fibrinogen alpha-alpha chain cross-linkage and has previously been associated with both increased risk of embolisation and increased resistance to thrombolysis. An association between this polymorphism and chronic thromboembolic pulmonary hypertension, therefore, supports an embolic aetiology for this disease, and may provide a mechanism by which thrombus persists following an acute event.

Hemorrhagic symptoms and bleeding risk in obligatory carriers of type 3 von Willebrand disease: an international, multicenter study.

OBJECTIVES: We undertook an international, multicenter study to describe the clinical picture and to estimate the bleeding risk in a group of obligatory carriers of type 3 von Willebrand disease (VWD). PATIENTS AND METHODS: Obligatory carriers (OC) of type 3 VWD were identified by the presence of offspring with type 3 VWD or by being an offspring of a type 3 patient. Normal controls were age- and sex-matched with the obligatory carriers. A physician-administered standardized questionnaire was used to evaluate hemorrhagic symptoms at presentation. A score system ranging from 0 (no symptom) to 3 (hospitalization, replacement therapy, blood transfusion) was used to quantitate bleeding manifestations. Odds ratios were computed for each symptom. RESULTS: Ten centers participated to the study, enrolling a total of 35 type 3 VWD families, with 70 OC. A total of 215 normal controls and 42 OC for type 1 VWD were also included. About 40% of type 3 OC had at least one bleeding symptom compared to 23% of normal controls and 81.8% of type 1 OC (P < 0.0001 by chi-squared test), showing that type 3 OC clearly represent a distinct population from type 1 OC. The clinical situations associated with an increase of bleeding risk in type 3 OC were epistaxis [odds ratio 3.6; 90% confidence intervals (CI) 1.84-21.5], cutaneous bleeding (odds ratio 5.5; 90% CI 2.5-14.1) and postsurgical bleeding (odds ratio 16.3; 90% CI 4.5-59). The severity of bleeding score correlated with the degree of factor (F) VIII reduction in plasma. CONCLUSIONS: OC for type 3 VWD represent a distinctive population from type 1 OC. These patients, however, present with more frequent bleeding symptoms in comparison to normal controls, especially in case of significantly low FVIII. Desmopressin and/or tranexamic acid might be useful to prevent or treat bleeding in these cases.

Update on the pathophysiology and classification of von Willebrand disease: a report of the Subcommittee on von Willebrand Factor.

von Willebrand disease (VWD) is a bleeding disorder caused by inherited defects in the concentration, structure, or function of von Willebrand factor (VWF). VWD is classified into three primary categories. Type 1 includes partial quantitative deficiency, type 2 includes qualitative defects, and type 3 includes virtually complete deficiency of VWF. VWD type 2 is divided into four secondary categories. Type 2A includes variants with decreased platelet adhesion caused by selective deficiency of high-molecular-weight VWF multimers. Type 2B includes variants with increased affinity for platelet glycoprotein Ib. Type 2M includes variants with markedly defective platelet adhesion despite a relatively normal size distribution of VWF multimers. Type 2N includes variants with markedly decreased affinity for factor VIII. These six categories of VWD correlate with important clinical features and therapeutic requirements. Some VWF gene mutations, alone or in combination, have complex effects and give rise to mixed VWD phenotypes. Certain VWD types, especially type 1 and type 2A, encompass several pathophysiologic mechanisms that sometimes can be distinguished by appropriate laboratory studies. The clinical significance of this heterogeneity is under investigation, which may support further subdivision of VWD type 1 or type 2A in the future.

The discriminant power of bleeding history for the diagnosis of type 1 von Willebrand disease: an international, multicenter study.

OBJECTIVE: The aim of this study was the validation of the criteria defining a significant mucocutaneous-bleeding history in type 1 von Willebrand disease (VWD). SUBJECTS AND METHODS: To avoid selection bias, 42 obligatory carriers (OC) of type 1 VWD were identified from a panel of 42 families with type 1 VWD enrolled by 10 expert centers. OC were identified by the presence of an offspring and another first degree relative with type 1 VWD (affected subjects, AFF). A standardized questionnaire was administered to evaluate hemorrhagic symptoms at the time of first examination, using a bleeding score ranging from 0 (no symptom) to 3 (hospitalization, replacement therapy, blood transfusion). Sensitivity, specificity, diagnostic likelihood ratios, positive and negative predictive values for the diagnosis of type 1 VWD were calculated from the data collected in OC and in 215 controls. RESULTS: Having at least three hemorrhagic symptoms or a bleeding score of 3 in males and 5 in females was very specific (98.6%) for the bleeding history of type 1 VWD, although less sensitive (69.1%). None of the misclassified OC had life-threatening bleeding episodes after diagnosis. CONCLUSIONS: We suggest that the use of a standardized questionnaire and bleeding score may be useful for the identification of subjects requiring laboratory evaluation for VWD.

Cysteine-mutations in von Willebrand factor associated with increased clearance.

BACKGROUND: von Willebrand disease (VWD) is a bleeding disorder caused by the decrease of functional von Willebrand factor (VWF). Low levels of VWF can result from decreased synthesis, impaired secretion, increased clearance or combinations thereof. Several mutations lead to impaired synthesis or secretion of VWF, however, little is known about the survival of VWF in the circulation. OBJECTIVES: To evaluate the effect of several VWF mutations on VWF clearance. PATIENTS/METHODS: The effect of three cysteine-mutations (C1130F, C1149R or C2671Y) on the in vivo survival of VWF was studied in patients carrying these mutations and in a VWF-deficient mice model. RESULTS: In patients carrying these mutations, we observed increased propeptide/mature VWF ratios and rapid disappearance of VWF from the circulation after desmopressin treatment. Detailed analysis of in vivo clearance of recombinant VWF in a VWF-deficient mice model revealed a fourfold increased clearance rate of the mutants. The mutations C1130F, C1149R and C2671Y are each associated with reduced survival of VWF in the circulation. Detailed analysis of the recombinant mutant VWF demonstrated that increased clearance was not due to increased proteolysis by ADAMTS-13. We did not identify functional or structural characteristics that the mutant proteins have in common and could be associated with the phenomenon of increased clearance. CONCLUSIONS: Cysteine-mutations in VWF may result in reduced in vivo survival. The observation that various mutations are associated with increased in vivo clearance may have major implications for the therapeutic strategies that rely on the rise of endogenous VWF after desmopressin administration.

Usefulness of patient interview in bleeding disorders.

BACKGROUND: It is not known which questions in a medical interview are most informative for diagnosing mild bleeding disorders, and what the value is of the entire interview in screening for hemostatic disorders. METHODS: A questionnaire was sent to 222 patients with a proven bleeding disorder, to 134 patients suspected of a bleeding disorder but whose hemostasis proved normal, and to 341 healthy volunteers. A first comparison, between patients with a bleeding disorder and patients with bleeding complaints whose hemostasis proved normal, mimics the situation in a department of hematology where patients are referred because of complaints. The second comparison, between patients with a proven bleeding disorder and healthy volunteers, may serve as a model for the situation where the interview is used as a screening tool to detect patients with a bleeding disorder in a population where there is no prior suspicion, eg, before surgical intervention. For each question we calculated a univariate odds ratio, multivariate odds ratios, and a positive and negative likelihood ratio. With a receiver operating characteristic curve analysis we evaluated the value of a simple vs an elaborate interview. RESULTS: Ninety-two percent of the questionnaires were returned. For both comparisons the most informative questions were questions about bleeding disorders in the family and traumatic events, with the exception of delivery. Noninformative questions were frequent gumbleeds and blood in the urine. A receiver operating characteristic curve analysis revealed that a simple interview has a high discriminating power in a screening situation, whereas in a referred situation even an elaborate interview has a low performance. CONCLUSIONS: A simple interview is useful as a screening tool for the dentist or surgeon. In a specialized hematology center with referred patients, however, the interview is of little value in identifying patients with a bleeding disorder.

Dimerization and multimerization defects of von Willebrand factor due to mutated cysteine residues.

In patients classified with type 1 and type 3 von Willebrand disease missense mutations resulting in the loss of cysteine residues in the D3-domain (multimerization area) and in the carboxy-terminus (dimerization area) of the von Willebrand factor (VWF) have been identified. We have investigated how these structural changes result in a quantitative VWF deficiency and how they interfere with the dimerization and multimerization processes. The effect of mutations in the multimerization area (C1130F, C1149R) and in the dimerization area (C2671Y, C2739Y, C2754W) of human recombinant VWF were investigated in transient transfection assays in 293T cells. All mutations resulted in reduced secretion of VWF in the medium and in intracellular retention. The amino-terminal mutants C1130F and C1149R showed impaired multimerization by lacking high molecular weight (HMW) multimers, in cotransfection experiments with wild-type (wt) VWF, the multimeric pattern was consistent with the pattern in the heterozygous type 1 patients. The carboxy-terminal mutants C2739Y and C2754W showed strongly reduced to nearly absent secretion of VWF, consistent with type 3 VWD. The multimeric pattern of C2739Y and C2754W is characterized by the absence of HMW multimers, an excess of monomers and intervening odd-numbered multimeric bands, indicating a dimerization defect. The carboxy-terminal mutant C2671Y is different, with mildly reduced secretion, intermediate intracellular retention and a normal multimerization pattern. We conclude that, in accordance with a phenotype of quantitative VWF deficiency, all cysteine mutants show impaired secretion, although the decrease of VWF in vitro appears lower than in the patients, suggesting additional, possibly heightened clearance, mechanisms in vivo.

Congenital von Willebrand disease type 3: clinical manifestations, pathophysiology and molecular biology.

von Willebrand disease type 3 is the most severe form of this condition. Patients present with a moderate-to-severe bleeding tendency. The plasma von Willebrand factor level in these patients is very low or undetectable. Although rare, von Willebrand disease type 3 is of major interest because of its severe clinical presentation, the need for replacement therapy and the risk of occurrence of alloantibodies after the infusion of plasma concentrates. The inheritance of type 3 disease is typically autosomal recessive. The parents are often consanguineous, although compound heterozygous inheritance does occur. The molecular basis of von Willebrand disease type 3 has recently been studied in detail, several molecular defects being identified. This chapter will focus on the clinical and molecular aspects of type 3 von Willebrand disease.

Inconsistency of association between type 1 von Willebrand disease phenotype and genotype in families identified in an epidemiological investigation.

In a previous epidemiological investigation among schoolchildren of Northern Italy, a conservative 1% prevalence of type 1 von Willebrand disease (VWD) was found. Diagnosis was based on a positive family history and low von Willebrand factor (VWF) ristocetin cofactor activity. To investigate whether the type 1 VWD phenotype as detected by our original methodology cosegregates with one or more specific alleles of the VWF gene, we have performed genotype analysis in affected subjects and their family members. Eleven of the 14 subjects previously identified as having VWD, all with mild personal bleeding symptoms, agreed to participate in the genetic study. Remarkably, the laboratory measurements of the previous investigation were completely confirmed in 10 of the 11 subjects. Clear cosegregation of the VWD type 1 and a specific VWF allele was observed in one family and was likely in the family of two other pro-bands. In three additional propositi and their families a possible association of the phenotype with a VWF allele was found. No association was observed in the remaining five subjects and their families. During 13-year follow-up few additional bleeding episodes were recorded among investigated subjects, most often occurring in the one family manifesting clear cosegregation. The results of this study illustrate that a personal and family bleeding history and persistently low VWF ristocetin cofactor activity, fitting the usual criteria for type 1 VWD, may not cosegregate with genetic markers at the VWF gene locus. Thus the prevalence of VWD defined as a disorder involving the VWF locus might be overestimated in population study. However, phenotypic diagnosis still remains fundamental to identify patients at risk of bleeding. Further research should clarify whether in families with more severe clinical and laboratory phenotype a clear association with markers of VWF is found.

Mutations in severe, type III von Willebrand's disease in the Dutch population: candidate missense and nonsense mutations associated with reduced levels of von Willebrand factor messenger RNA.

The von Willebrand factor (vWF) genes of nine unrelated, severe, type III von Willebrand's disease (vWD) patients (six of Dutch origin) and four unrelated Dutch type I vWD patients were screened for mutations in exons that contain CGA codons (Arg), which are liable to mutation to TGA stop codons. The nine exons of the vWF gene (3, 8, 9, 10, 28, 31, 32, 43 and 45) that contain all the CGA codons (11 in total) of the vWF cDNA were amplified by the polymerase chain reaction and screened for mutations by single-strand conformation polymorphism analysis, restriction enzyme - and/or nucleotide sequence analysis. Three of the severe vWD patients were found to be heterozygous for a nonsense mutation: CGA Arg 2535-->TGA Stop. Three other severe vWD patients were homozygous for a single nucleotide substitution, AAC Asn 2546-->TAC Tyr. The transcription of these mutated alleles was tested by cDNA dependent amplification of platelet RNA. The level of transcription product was strongly reduced for either mutant allele.

Characterization of the genetic defects in recessive type 1 and type 3 von Willebrand disease patients of Italian origin.

The genetic defects causing recessive type 1 and type 3 von Willebrand disease (VWD) in eight families from the northern part of Italy have been investigated. Mutations were identified in 14 of the 16 disease-associated von Willebrand factor (VWF) genes. Only one mutation, a stop codon in exon 45, was previously reported. Several new mutations were identified: one cytosine insertion in exon 42, one guanine deletion in exon 28, one probably complete VWF gene deletion, one substitution in the 3' splice site of intron 13, one possible gene conversion, and three candidate missense mutations. One missense mutation, the substitution of a cysteine in exon 42, was identified in all type 3 VWD patients that were previously characterized as a subgroup with significant increase of factor VIII procoagulant activity after desmopressin infusion. This paper demonstrates again that the molecular defects of quantitative VWD are diverse and located throughout the entire VWF gene.

A standard nomenclature for von Willebrand factor gene mutations and polymorphisms. On behalf of the ISTH SSC Subcommittee on von Willebrand factor.

Examination of the entire von Willebrand factor (VWF) gene for mutations, particularly in types 1 and 3 von Willebrand disease (VWD) is becoming more widely practised. The sequence of the entire VWF gene will soon be compiled as a single sequence. For these reasons, a clearly defined nomenclature to use for numbering the VWF nucleotide and amino acid sequence is required. The following recommendations are made for VWF numbering. VWF cDNA nucleotide sequence should be numbered from the A of the initiator ATG as the +1 position. Genomic DNA should be prefixed with a "g" and also numbered from this position. Amino acid (aa) numbering should be from the initiator methionine as the +1 position with sequential numbering of aa throughout VWF. To avoid confusion with previously used numbering schemes for mature VWF, which started from serine 764 of pre-pro VWF, the use of the single letter amino acid code is recommended.

Familial clustering of factor VIII and von Willebrand factor levels.

Recently, we found that high levels of clotting factor VIII (>150 IU/dl) are common and make an important contribution to thrombotic risk. The determinants of high factor VIII:C are unclear and might be partly genetic. Therefore, we tested the influence of age, blood group and von Willebrand factor (VWF) levels on factor VIII:C levels, and investigated whether factor VIII:C levels are genetically determined. We performed an analysis of 564 female relatives of hemophilia A patients, who had visited our center for genetic counseling. In univariate analysis, AB0 blood group, age and VWF antigen (VWF:Ag) levels all influenced factor VIII:C levels. After adjustment for the effect of VWF:Ag levels, both blood group and age still had an effect on factor VIII:C levels. In sister pairs, the Pearson correlation coefficient between factor VIII:C levels was 0.17 (p = 0.024) and this correlation remained positive (0.15, p = 0.046) after correction for the influence of VWF:Ag. In mother-daughter pairs, no correlation of factor VIII:C levels was found. The correlation of VWF:Ag levels in sisterpairs was 0.41 (p <0.001) and in mother-daughter pairs 0.44 (p <0.001), in line with the assumption that VWF:Ag levels are under control of autosomal genes. Familial influence on plasma factor VIII:C and VWF:Ag levels was investigated with a recently developed familial aggregation test. This test verifies whether familial aggregation of a particular parameter exists in a set of pedigrees. In 435 women from 168 families, factor VIII:C as well as VWF:Ag levels correlated significantly within families, which suggests a familial influence. The familial aggregation was more prominent for VWF:Ag levels than for factor VIII:C levels, possibly because the genetic effect on VWF:Ag levels is larger than on factor VIII:C levels. Our results support the presence of a familial influence on factor VIII:C as well as on VWF:Ag levels.

Increased levels of factor VIII and fibrinogen in patients with venous thrombosis are not caused by acute phase reactions.

Factor VIII activity (factor VIII:C) levels > or =150 IU/dl are associated with a 5- to 6-fold increased risk of venous thrombosis compared to levels <100 IU/dl, and fibrinogen levels > or =5.0 g/l increase the thrombosis risk 4-fold. These high levels are present in 25% resp. 3% of the patients with a first episode of venous thrombosis. These findings were based on measurements after the thrombotic event, so the factor VIII and fibrinogen levels in thrombosis patients may have been influenced by acute phase reactions or ongoing inflammatory responses. In the present study we measured plasma C-reactive protein (CRP) as a sensitive marker of an acute phase reaction in 474 thrombosis patients and 474 age- and sex-matched healthy controls, that were part of the Leiden Thrombophilia Study (LETS). Mean and median CRP levels were higher in thrombosis patients than in the controls, suggesting inflammation in some patients. CRP affected both factor VIII and fibrinogen levels, in patients and controls alike. After adjustment for the effect of CRP, high factor VIII:C levels still increased the thrombosis risk 6-fold and high fibrinogen levels 4-fold, which is for both very similar to the risk before correction for CRP levels. These results show that although systemic inflammation may be present in some of the patients, elevated levels of factor VIII:C and fibrinogen were in general not caused by acute phase reactions. This further supports a causal relationship between both high factor VIII:C and fibrinogen levels and venous thrombosis.

Impact of von Willebrand disease on health-related quality of life in a pediatric population.

BACKGROUND: Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder. Whether VWD is associated with health-related quality of life (HR-QoL) in children is unknown. OBJECTIVES: This nationwide cross-sectional study measured HR-QoL in children with moderate or severe VWD. Our primary aim was to compare HR-QoL of VWD patients with that of reference populations. Additionally, we studied the impact of bleeding phenotype and VWD type on HR-QoL. METHODS: HR-QoL was assessed with the Infant/Toddler QoL Questionnaire (0-5 years) and Child Health Questionnaire (6-15 years), and compared with reference population scores. Multivariate analysis was used to evaluate the influence of type of VWD and bleeding phenotype on HR-QoL scores. RESULTS: Preschool children (0-5 years, n = 46) with VWD had lower HR-QoL scores for general health perceptions and parental time than reference populations. School children (6-15 years, n = 87) with VWD had lower scores for physical functioning, role functioning - emotional/behavioral, general health perceptions, and physical summary. Type of VWD was associated with HR-QoL in school children for bodily pain, general health perceptions, parental emotion, family activities, and physical summary. Scores of children with type 3 VWD were, on average, 15 points lower than those of the reference population on the above-mentioned scales. A more severe bleeding phenotype was associated with a lower score on 11/15 physical, emotional and social scales. CONCLUSION: HR-QoL is lower in VWD children than in reference populations, in particular in school children. The negative impact of VWD is sensitive to type of VWD and bleeding phenotype; as well as physical scales, emotional and social scales are affected.

Gynaecological and obstetric bleeding in moderate and severe von Willebrand disease.

A nation-wide cross-sectional study was initiated to assess gynaecological and obstetrical symptoms in an unselected cohort of women with moderate and severe von Willebrand disease (VWD) in the Netherlands. A total of 423 women aged ≥16 years were included. Bleeding severity was measured using the Tosetto Bleeding Score (BS). Menorrhagia, defined as occurrence of ≥2 menorrhagia symptoms, was reported by 81%. Of all VWD women, 78% received any kind of treatment for menorrhagia and 20% underwent a hysterectomy predominantly because of severe menstrual bleeding. Over half of the women reported more blood loss than can be expected with a normal delivery. In 52% of reported pregnancy losses curettage was needed because of bleeding. Mean number of live births was 1.9, which is comparable with the general Dutch population. In conclusion, women with moderate or severe VWD frequently have menorrhagia in need of treatment, and 20% of the VWD women underwent a hysterectomy. Bleeding complications occurred in over 50% of the women after childbirth or pregnancy loss. Progeny seems not to be affected in women with moderate or severe VWD.