The prevalence of symptomatic von Willebrand disease in primary care practice

[Clinical observation of desmopressin in the treatment of 15 patients with DDAVP]

Objective: To assess the significance of DDAVP use in the diagnosis and treatment of VWD. Methods: An analysis of 15 VWD cases who referred to Hematology Division of First affiliated Hospital of Soochow University and treated with DDAVP from March 2016 to August 2018 was conducted. Efficacy and treatment response of DDAVP were monitored by observations of changes in factor Ⅷ procoagulant (FⅧ∶C) and von Willebrand Factor (VWF) related indicators before and 2 h after DDAVP injection. Results: Of 15 cases with VWD, 7 males and 8 females with a median age of 23 (6-46) years, 7 of 9 type I VWD patients achieved complete response (CR) , 1 type 2A VWD case CR, 5 type 3 VWD ones no response (NR) . The VWF multimer analysis in 5 patients combined with other plasma VWF values were in accordance with the known diagnosis. Conclusions: DDAVP was effective in most type 1 patients, and ineffective in some type 2 and almost all type 3 cases. It was helpful for diagnosis and subsequent treatment planning.

How I treat low von Willebrand factor levels

Partial quantitative deficiency of plasma von Willebrand factor (VWF) is responsible for the majority of cases of von Willebrand disease (VWD), the most common inherited human bleeding disorder. International consensus guidelines recommend that patients with reduced plasma VWF antigen (VWF:Ag) levels and bleeding phenotypes be considered in 2 distinct subsets. First, patients with marked reductions in plasma VWF levels (<30 IU/dL) usually have significant bleeding phenotypes and should be classified with “type 1 VWD.” In contrast, patients with intermediate reduced plasma VWF levels (in the range of 30-50 IU/dL) should be considered in a separate category labeled “low VWF levels.” These patients with low VWF commonly display variable bleeding phenotypes and often do not have VWF gene sequence variations. Because the pathophysiology underlying low VWF levels remains largely undefined, diagnosis and management of these patients continue to pose significant difficulties. In this article, we present a number of clinical case studies to highlight these common clinical challenges. In addition, we detail our approach to establishing a diagnosis in low VWF patients and discuss strategies for the management of these patients in the context of elective surgery and pregnancy.

Diagnostic challenges of inherited mild bleeding disorders: a bait for poorly explored clinical and basic research

The best-known inherited mild bleeding disorders (MBDs), i.e. type 1 von Willebrand disease (VWD), platelet function disorders (PFDs), and mild to moderate clotting factor deficiencies, are characterized clinically by mucocutaneous bleeding, and, although they are highly prevalent, still pose difficult diagnostic problems. These include establishing the pathological nature of bleeding, and the uncertainties surrounding the clinical relevance of laboratory results. Furthermore, the high frequency of bleeding symptoms in the normal population and the subjective appraisal of symptoms by patients or parents makes elucidating the pathological nature of bleeding difficult. Standardized bleeding assessment tools and semiquantitative bleeding scores (BSs) help to discriminate normal from abnormal bleeding. However, as most MBDs have similar bleeding patterns, for example, bleeding sites, frequency, and severity, BSs are of little help for diagnosing specific diseases. Global tests of primary hemostasis (bleeding time; PFA-100/200) lack sensitivity and, like BSs, are not disease-specific. Problems with the diagnosis of type 1 VWD and PFD include assay standardization, uncertain definition of von Willebrand factor cut-off levels, and the lack of universal diagnostic criteria for PFD. Regarding clotting factor deficiencies, the bleeding thresholds of some coagulation factors, such as factor VII and FXI, are highly variable, and may lead to misinterpretation of the clinical relevance of mild to moderate deficiencies. Remarkably, a large proportion of MBDs remain undiagnosed even after comprehensive and repeated laboratory testing. These are tentatively considered to represent bleeding of undefined cause, with clinical features indistinguishable from those of classical MBD; the pathogenesis of this is probably multifactorial, and unveiling these mechanisms should constitute a fertile source of translational research.

Blood inflammatory and endothelial markers in women with von Willebrand disease

Introduction

VWD-affected females often experience menorrhagia. Periodical fluctuations of the sex steroids during the menstrual cycle cause changes both in the coagulation and immune system. The aim of the current study was to assess the changes in selected inflammatory and endothelial markers in women with VWD during two phases of the menstrual cycle (follicular and luteal) and to compare it with corresponding data from healthy controls.

Materials and methods

The study group included 12 VWD-affected females with regular menstrual cycle, with none of them being prescribed hormone treatment. They were not pregnant or breastfeeding. The control group consisted of 102 healthy females, matched for age and BMI.

Results

Within the VWD group, endostatin was higher during the follicular phase, compared to the luteal phase, although the difference was not significant (p = 0.062). sICAM-1 and IL-6 were higher in VWD-affected females, compared to the controls, sVCAM-1, cathepsin S and sP-selectin were lower (p<0.003 for all cases). The pattern was constant throughout the menstrual cycle.

Conclusions

Higher levels of endostatin during early follicular phase could potentially predispose women with VWD to the development of heavy menstrual bleeding, due to antiangiogenic properties and ability to suppress several coagulation factors. Lower p-selectin levels in VWD group, compared to controls, may also contribute to the bleeding tendency. Changes in other proteins, involved in angiogenesis are hypothetically related to the formation of angiodysplasia—common complication of VWF deficiency. The latter statement requires confirmation in larger studies.

Closing the gap - detection of clinically relevant von Willebrand disease in emergency settings through an improved algorithm based on rotational Thromboelastometry

Background

Hemorrhage and blood loss are still among the main causes of preventable death. Global hemostatic assays are useful point-of-care test (POCT) devices to rapidly detect cumulative effects of plasma factors and platelets on coagulation. Thromboelastography (TEG) and Thromboelastometry (ROTEM) are established methods in many anesthesiological departments for guided hemostatic treatment. However, von Willebrand disease remains undetected by standard ROTEM, especially during emergency care, despite being the most prevalent congenital hemostatic disorder.

Methods

In our monocentric cohort pilot study we focused on hemostatic challenges associated with von Willebrand disease. Twenty-seven patients with suspected von Willebrand disease were included. We modified the routine ROTEM assay by adding a preincubation with ristocetin and commercially available plasma-derived von Willebrand factor to identify clinically relevant von Willebrand disease (VWD).

Results

Addition of von Willebrand factor to the ristocetin assay of a VWD type 3 patient restored the reaction of the whole blood probe to match the response of a healthy person. Our modified ROTEM assay with ristocetin (Ricotem) showed that all high responders (n = 7) had VWD. In the low responder group (n = 16) – 10 of 16 had VWD and in the normal responder group (n = 5), 2 of 5 had mild type 1 VWD.

Conclusions

This new modification of the standard ROTEM assay enables the detection of otherwise unnoticed critical von Willebrand disease based on alterations in clot formation and might serve as a novel approach to reliably assess severe VWD patients by platelet-mediated blood clotting in an emergency setting. We recommend incorporating this new VWD-focused screening tool into the current ROTEM-based management algorithm of acute microvascular bleeding.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0672-8) contains supplementary material, which is available to authorized users.

Genetic regulation of plasma von Willebrand factor levels in health and disease

Plasma levels of the multimeric glycoprotein von Willebrand factor (VWF) constitute a complex quantitative trait with a continuous distribution and wide range in the normal population (50-200%). Quantitative deficiencies of VWF (< 50%) are associated with an increased risk of bleeding, whereas high plasma levels of VWF (> 150%) influence the risk of arterial and venous thromboembolism. Although environmental factors can strongly influence plasma VWF levels, it is estimated that approximately 65% of this variability is heritable. Interestingly, although variability in VWF can account for ~ 5% of the genetic influence on plasma VWF levels, other genetic loci also strongly modify plasma VWF levels. The identification of the additional sources of VWF heritability has been the focus of recent observational trait-mapping studies, including genome-wide association studies or linkage analyses, as well as hypothesis-driven research studies. Quantitative trait loci influencing VWF glycosylation, secretion and clearance have been associated with plasma VWF antigen levels in normal individuals, and may contribute to quantitative VWF abnormalities in patients with a thrombotic tendency or type 1 von Willebrand disease (VWD). The identification of genetic modifiers of plasma VWF levels may allow for better molecular diagnosis of type 1 VWD, and enable the identification of individuals at increased risk for thrombosis. Validation of trait-mapping studies with in vitro and in vivo methodologies has led to novel insights into the life cycle of VWF and the pathogenesis of quantitative VWF abnormalities.

Thrombin generation during a regular menstrual cycle in women with von Willebrand disease

Fluctuations of the sex steroids during the menstrual cycle might significantly influence hemostasis. This association, derived from a number of the observations on healthy women, is yet to be described in females affected by bleeding disorders. The aim of the current study was to assess the changes in hemostatic variables in women with vWD during two phases of the menstrual cycle (follicular and luteal) and to compare it with healthy controls. The study group included 12 vWD-affected females with regular menstrual cycle, with none of them being prescribed any hormonal treatment. The control group consisted of 102 healthy females, matched for age and BMI. Within the vWD group FVIII and FX were both significantly higher during follicular phase than in luteal phase (p = 0.013 and p = 0.033 respectively). AT, FII, FVII and FX were higher in women with vWD, compared with controls during both phases of the menstrual cycle (p < 0.0005, p < 0.0005, p = 0.001 and p < 0.0005). In women with vWD, lag time and time to peak were prolonged during both phases of the menstrual cycle(p < 0.0005), while peak thrombin concentration was reduced (p = 0.003 and p = 0.002 during follicular and luteal phase respectively) compared to healthy peers. Lower levels of FVIII and FX during luteal phase may predispose women to the development of the menorrhagia - common complication of vWD. Women with vWD need more time to reach the peak thrombin concentration, while the latter still remains less than in healthy women. Higher levels of AT in vWD-affected females, compared to controls, may also contribute to the existing bleeding tendency in this cohort.

Type-3 von Willebrand disease in India-Clinical spectrum and molecular profile

INTRODUCTION

Type 3 von Willebrand disease (VWD) is the rare and most severe form of VWD which results from a near-complete deficiency of the von Willebrand factor (VWF). This study evaluates in detail the molecular pathology of type-3 VWD in India. One hundred and two patients from 90 families were evaluated.

PATIENTS AND METHODS

Phenotypic data, including bleeding scores (BS), were documented using structured questionnaires. Diagnosis of type 3 VWD was based on undetectable VWF antigen levels in the plasma. Genomic DNA from these patients was screened for mutations in VWF gene. Structural modeling and expression studies were carried out for missense mutations.

RESULTS

Out of 102 patients, mutations could be identified in 91% (n = 93). Fifty-five different gene variants were identified. Thirty-four (61.8%) were novel. Mutations could be identified in both the alleles in 90 patients, while no causative mutation could be identified in 9 patients; twenty-four (23.5%) patients had mutations clustered in the propeptide region of VWF. Interestingly, five mutations accounted for the defects in 37/93 (39.8%) patients. Structural analysis and in vitro studies on missense mutations imply impaired processes associated with secretion of VWF.

CONCLUSION

This study is one of the largest series to define the molecular basis of type-3 VWD.

Current issues in diagnosis and treatment of von Willebrand disease

Clinically, von Willebrand disease (VWD) presents as mucosal bleeding caused by a decreased quantity or quality of von Willebrand factor (VWF). Diagnosis of VWD requires careful consideration of patient specific factors, bleeding symptoms, and laboratory results. Patients with borderline low VWF levels remain challenging, given that low VWF is not necessarily a guarantee of bleeding, but is present in many patients with symptoms, and treatment of low VWF may improve bleeding. Laboratory diagnosis of VWD is complex and no single test can determine the presence or absence of functional VWF. Historically, VWF binding to platelet GPIbα was measured by the ristocetin cofactor assay (VWF:RCo); a new assay using platelet GPIbα in the absence of ristocetin (VWF:GPIbM) is gradually replacing the VWF:RCo due to improved accuracy in diagnosis. VWF binding to collagen is a separate function, and requires specific testing to determine if a collagen binding defect is present. Regardless of these laboratory complexities, clinicians can empirically treat VWD to alleviate bleeding symptoms by raising VWF levels through desmopressin or VWF concentrate. Recombinant VWF is now available, but clinicians may need to add an initial dose of FVIII when treating emergency bleeds.

Advances in the diagnosis and treatment of Von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder, yet diagnosis and management remain challenging. Development and use of bleeding assessment tools allows for improved stratification of which patients may require further assessment and which patients are most likely to require treatment of their VWD. New options for laboratory assessment of von Willebrand factor (VWF) activity include a new platelet-binding assay, the VWF:GPIbM, which is subject to less variability than the ristocetin cofactor activity assay, and collagen-binding assays that provide insight into a different function of VWF. Genetic testing may be helpful in some cases where a type 2 VWD variant is suspected but is usually not helpful in type 1 VWD. Finally, treatment options for VWD are reviewed, including the use of recombinant VWF. Despite these advances, still more work is required to improve diagnosis, treatment, and quality of life for affected patients.

Advances in the diagnosis and treatment of Von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder, yet diagnosis and management remain challenging. Development and use of bleeding assessment tools allows for improved stratification of which patients may require further assessment and which patients are most likely to require treatment of their VWD. New options for laboratory assessment of von Willebrand factor (VWF) activity include a new platelet-binding assay, the VWF:GPIbM, which is subject to less variability than the ristocetin cofactor activity assay, and collagen-binding assays that provide insight into a different function of VWF. Genetic testing may be helpful in some cases where a type 2 VWD variant is suspected but is usually not helpful in type 1 VWD. Finally, treatment options for VWD are reviewed, including the use of recombinant VWF. Despite these advances, still more work is required to improve diagnosis, treatment, and quality of life for affected patients.

A comparative evaluation of a new fully automated assay for von Willebrand factor collagen binding activity to an established method

INTRODUCTION

Laboratory diagnosis of von Willebrand disease (VWD) is made by the measurement of von Willebrand factor (VWF) protein level and its activities. Current VWF activity tests include ristocetin cofactor and collagen binding (VWF:CB) assays.

AIM

We have undertaken an evaluation of a new fully automated VWF:CB assay relative to an established enzyme-linked immunosorbent assay (ELISA) method.

METHODS

The two analytical systems operate with different detection principles: a chemiluminescent method performed on ACL AcuStar Analyzer (the former) and a colorimetric ELISA by Asserachrom Stago (the latter) (type III collagen from human placenta). The HemosIL AcuStar VWF:CB assay is a chemiluminescent 2-step immunoassay that uses magnetic particles coated with a type III collagen triple-helical peptide. VWF:CB levels were determined in 50 healthy subjects and 100 VWD patients (22 type 1, 73 type 2 and 5 type 3).

RESULTS

Eleven VWD samples reported VWF:CB values below the lower detection limit of one or both methods. The new method showed a good correlation with the ELISA method (r > .9, mean bias 3.85 IU/dL) in both healthy and VWD samples. One of 150 samples gave inconsistent results using the two assays, leading to an uncertain diagnosis of VWD type 1 (ELISA method) or type 2 MCB (fully automated method).

CONCLUSION

The new assay is rapid and simple to use, with its ready-to-use reagent cartridges. This VWF:CB assay, in addition to the measurement of VWF:Ag and VWF:RCo made on the same platform, gives additional information for the diagnosis of VWD in both nonspecialized and reference laboratories.

How much do we really know about von Willebrand disease?

PURPOSE OF REVIEW

In the last nine decades, large advances have been made toward the characterization of the pathogenic basis and clinical management of von Willebrand disease (VWD), the most prevalent inherited bleeding disorder. Pathological variations at the von Willebrand factor (VWF) locus present as a range of both quantitative and qualitative abnormalities that make up the complex clinical spectrum of VWD. This review describes the current understanding of the pathobiological basis of VWD.

RECENT FINDINGS

The molecular basis of type 2 (qualitative abnormalities) and type 3 VWD (total quantitative deficiency) have been well characterized in recent decades. However, knowledge of type 1 VWD (partial quantitative deficiency) remains incomplete because of the allelic and locus heterogeneity of this trait, and is complicated by genetic variability at the VWF gene, interactions between the VWF gene and the environment, and the involvement of external modifying loci. Recent genome wide association studies and linkage analyses have sought to identify additional genes that modify the type 1 VWD phenotype.

SUMMARY

Understanding the pathogenic basis of VWD will facilitate the development of novel treatment regimens for this disorder, and improve the ability to provide complementary molecular diagnostics for type 1 VWD.

Novel insights into the clinical phenotype and pathophysiology underlying low VWF levels

Critical clinical questions remain unanswered regarding diagnosis and management of patients with low von Willebrand factor (VWF) levels (30-50 IU/dL). To address these questions, the Low VWF Ireland Cohort (LoVIC) study investigated 126 patients registered with low VWF levels. Despite marginally reduced plasma VWF levels, International Society of Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH BAT) confirmed significant bleeding phenotypes in the majority of LoVIC patients. Importantly, bleeding tendency did not correlate with plasma VWF levels within the 30 to 50 IU/dL range. Furthermore, bleeding phenotypes could not be explained by concurrent hemostatic defects. Plasma factor VIII to VWF antigen (VWF:Ag) ratios were significantly increased in LoVIC patients compared with controls (P < .0001). In contrast, VWF propeptide to VWF:Ag ratios >3 were observed in only 6% of the LoVIC cohort. Furthermore, platelet-VWF collagen binding activity levels were both significantly reduced compared with controls (P < .05). In response to 1-desamino-8-D-arginine vasopressin (DDAVP), peak VWF:Ag levels exceeded 100 IU/dL in 88% of patients and was sustained >100 IU/dL after 4 hours in 72% of subjects. In conclusion, our novel data suggest that low VWF levels can be associated with significant bleeding and are predominantly due to reductions in VWF synthesis and/or constitutive secretion. Although enhanced VWF clearance may contribute to the pathophysiology in some individuals, the absolute reduction in VWF plasma half-life is usually mild and not sufficient to significantly impact upon the duration of DDAVP-induced VWF response. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

Angiodysplasia in von Willebrand Disease: Understanding the Clinical and Basic Science

Severe and intractable gastrointestinal bleeding caused by angiodysplasia is a debilitating problem for up to 20% of patients with von Willebrand disease (VWD). Currently, the lack of an optimal treatment for this recurrent problem presents an ongoing challenge for many physicians in their management of affected patients. Over the past few years, studies have pointed to a regulatory role for the hemostatic protein, von Willebrand factor (VWF), in angiogenesis, providing a novel target for the modulation of vessel development. This article will review the clinical implications and molecular pathology of angiodysplasia in VWD.

Blood volume-based von Willebrand factor to prevent postpartum hemorrhage in von Willebrand disease

Publisher's Note: This article has a companion Point by Kouides. Publisher's Note: Join in the discussion of these articles at Blood Advances Community Conversations.

Obstetric bleeding among women with inherited bleeding disorders: a retrospective study

INTRODUCTION

Women with inherited bleeding disorders are at increased risk for bleeding complications during pregnancy and the postpartum period, particularly postpartum haemorrhage (PPH).

AIM

This retrospective study evaluates pregnancy management through the Inherited Bleeding Disorders Clinic of Southeastern Ontario, the clinical factors associated with pregnancy-related abnormal bleeding and assesses tranexamic acid use in the postpartum treatment of bleeding disorder patients.

METHODS

A chart review of 62 pregnancies, from 33 women, evaluated patient characteristics (age, haemostatic factor levels) and delivery conditions (mode of delivery, postpartum treatment) in relation to abnormal postpartum bleeding.

RESULTS

This cohort revealed increased risk of immediate PPH with increased age at delivery (mean age: 30.1 years with PPH, 26.5 years without PPH, P < 0.013), and birth by vaginal delivery (P < 0.042). Low von Willebrand factor (VWF) antigen or factor VIII (FVIII) in the third trimester was not associated with an increased risk of PPH; however, low VWF:RCo was associated with increased immediate PPH despite treatment with continuous factor infusion (P < 0.042). Women treated with tranexamic acid postpartum had less severe bleeding in the 6-week postpartum (P < 0.049) with no thrombotic complications.

CONCLUSIONS

This study contributes to the growing body of work aimed at optimizing management of bleeding disorder patients through pregnancy and the postpartum period, showing patients are at a higher risk of PPH as they age. Risk factors such as low third trimester VWF:RCo have been identified. Treatment with tranexamic acid in the postpartum period is associated with a reduced incidence of abnormal postpartum bleeding.

Characterization of aberrant splicing of von Willebrand factor in von Willebrand disease: an underrecognized mechanism

Approximately 10% of von Willebrand factor (VWF) gene mutations are thought to alter messenger RNA (mRNA) splicing through disruption of consensus splice sites. This mechanism is likely underrecognized and affected by mutations outside consensus splice sites. During VWF synthesis, splicing abnormalities lead to qualitative defects or quantitative deficiencies in VWF. This study investigated the pathologic mechanism acting in 3 von Willebrand disease (VWD) families with putative splicing mutations using patient-derived blood outgrowth endothelial cells (BOECs) and a heterologous human embryonic kidney (HEK 293(T)) cell model. The exonic mutation c.3538G>A causes 3 in-frame splicing variants (23del, 26del, and 23/26del) which cannot bind platelets, blood coagulation factor VIII, or collagen, causing VWD through dominant-negative intracellular retention of coexpressed wild-type (WT) VWF, and increased trafficking to lysosomes. Individuals heterozygous for the c.5842+1G>C mutation produce exon 33 skipping, exons 33-34 skipping, and WT VWF transcripts. Pathogenic intracellular retention of VWF lacking exons 33-34 causes their VWD. The branch site mutation c.6599-20A>T causes type 1 VWD through mRNA degradation of exon 38 skipping transcripts. Splicing ratios of aberrant transcripts and coexpressed WT were altered in the BOECs with exposure to shear stress. This study provides evidence of mutations outside consensus splice sites disrupting splicing and introduces the concept that VWF splicing is affected by shear stress on endothelial cells.

Heavy menstrual bleeding and health-associated quality of life in women with von Willebrand's disease

Women with the inherited bleeding disorder von Willebrand's disease (VWD) face gender-specific hemostatic challenges during menstruation. Heavy menstrual bleeding (HMB) can negatively affect their overall life activities and the health-associated quality of life. The purpose of the present study was to investigate whether women with VWD experienced HMB and an impaired health-associated quality of life. The study subjects were recruited from the Coagulation Unit of Karolinska University Hospital. Information was retrieved from various self-administered forms and medical records. Of the 30 women (18-52 years) that were included in the present study, 50% suffered from HMB, although the majority received treatment for HMB. In addition, almost all the included women perceived limitations in the overall life activities due to menstruation. The health-associated quality of life for women with HMB was significantly lower (P<0.10) with regards to 'bodily pain' compared with Swedish women of the general population. In conclusion, women with VWD experienced reduced health-associated quality of life as a result of HMB. Therefore, preventing limitations in overall life activities and improving their health-associated quality of life thorough counseling on menstrual bleeding is important for women with VWD.

Clinical and laboratory variability in a cohort of patients diagnosed with type 1 VWD in the United States

von Willebrand disease (VWD) is the most common inherited bleeding disorder, and type 1 VWD is the most common VWD variant. Despite its frequency, diagnosis of type 1 VWD remains the subject of debate. In order to study the spectrum of type 1 VWD in the United States, the Zimmerman Program enrolled 482 subjects with a previous diagnosis of type 1 VWD without stringent laboratory diagnostic criteria. von Willebrand factor (VWF) laboratory testing and full-length VWF gene sequencing was performed for all index cases and healthy control subjects in a central laboratory. Bleeding phenotype was characterized using the International Society on Thrombosis and Haemostasis bleeding assessment tool. At study entry, 64% of subjects had VWF antigen (VWF:Ag) or VWF ristocetin cofactor activity below the lower limit of normal, whereas 36% had normal VWF levels. VWF sequence variations were most frequent in subjects with VWF:Ag <30 IU/dL (82%), whereas subjects with type 1 VWD and VWF:Ag ≥30 IU/dL had an intermediate frequency of variants (44%). Subjects whose VWF testing was normal at study entry had a similar rate of sequence variations as the healthy controls (14%). All subjects with severe type 1 VWD and VWF:Ag ≤5 IU/dL had an abnormal bleeding score (BS), but otherwise BS did not correlate with VWF:Ag. Subjects with a historical diagnosis of type 1 VWD had similar rates of abnormal BS compared with subjects with low VWF levels at study entry. Type 1 VWD in the United States is highly variable, and bleeding symptoms are frequent in this population.

Using genetic diagnostics in hemophilia and von Willebrand disease

Most bleeding disorders encountered in clinical practice will be diagnosed, at least initially, by phenotypic assays. However, since the characterization of the genes that encode coagulation factors in the 1980s, significant progress has been made in translating this knowledge for diagnostic and therapeutic purposes. For hemophilia A and B, molecular genetic testing to determine carrier status, prenatal diagnosis, and likelihood of inhibitor development or anaphylaxis to infused coagulation factor concentrates is an established component of comprehensive clinical management. In contrast, although significant recent advances in our understanding of the molecular genetic basis of von Willebrand disease (VWD) have allowed for the development of rational approaches to genetic diagnostics, questions remain about this complex genetic disorder and how to incorporate emerging knowledge into diagnostic strategies. This article will review the state-of-the-art for molecular diagnostics for both hemophilia and VWD.

Bleeding spectrum in children with moderate or severe von Willebrand disease: Relevance of pediatric-specific bleeding

The bleeding phenotype of children with von Willebrand disease (VWD) needs to be characterized in detail to facilitate diagnosis during childhood and aid in the planning and assessment of treatment strategies. The objective was to evaluate the occurrence, type, and severity of bleeding in a large cohort of children with moderate and severe VWD. We included 113 children (aged 0-16 years) with Type 1 (n = 60), 2 (n = 44), and 3 (n = 9) VWD with von Willebrand factor (VWF) antigen and/or VWF ristocetin cofactor levels ≤ 30 U/dL from a nation-wide cross-sectional study ("Willebrand in the Netherlands" study). Bleeding severity and frequency were determined using the International Society on Thrombosis and Hemostasis-Bleeding Assessment Tool (ISTH-BAT) with supplementary pediatric-specific bleeding symptoms (umbilical stump bleeding, cephalohematoma, cheek hematoma, conjunctival bleeding, postcircumcision and postvenipuncture bleeding). We found that all 26 postmenarche girls experienced menorrhagia. Other common bleedings were cutaneous (81%), oropharyngeal (64%), prolonged bleeding from minor wounds (58%), and epistaxis (56%). Pediatric-specific bleeding symptoms were present in 44% of patients. ISTH-BAT bleeding score was higher in index cases than in affected family members (median, 12.0 vs. 6.5, P < 0.001), higher in Type 3 VWD than in Type 2 or 1 (17.0 vs. 10.5 or 6.5, P < 0.001) and higher in children with severe (<10 U/dL) than moderate VWD (10-30 U/dL) (11.0 vs. 7.0, P < 0.001). Frequency of any bleeding, epistaxis, and oral cavity was higher in types 2 and 3 than in Type 1 VWD and was associated with VWF levels. We conclude that pediatric-specific bleeding symptoms occurred in a large proportion of children with moderate or severe VWD and should be included when evaluating children for VWD.

Genetic heterogeneity in a large cohort of Indian type 3 von Willebrand disease patients

Background

Though von Willebrand disease (VWD) is a common coagulation disorder, due to the complexity of the molecular analysis of von Willebrand factor gene (VWF), not many reports are available from this country. Large size of the gene, heterogeneous nature of mutations and presence of a highly homologous pseudogene region are the major impediments in the genetic diagnosis of VWD. The study is aimed at unravelling the molecular pathology in a large series of VWD patients from India using an effective strategy.

Method

We evaluated 85 unrelated Indian type 3 VWD families to identify the molecular defects using a combination of techniques i.e. PCR-RFLP, direct DNA sequencing and multiple ligation probe amplification (MLPA).

Results

Mutations could be characterized in 77 unrelated index cases (ICs). 59 different mutations i.e. nonsense 20 (33.9%), missense 13 (22%), splice site 4 (6.8%), gene conversions 6 (10.2%), insertions 2 (3.4%), duplication 1 (1.7%), small deletions 10 (17%) and large deletions 3 (5.1%) were identified, of which 34 were novel. Two common mutations i.e. p.R1779* and p.L970del were identified in our population with founder effect. Development of alloantibodies to VWF was seen in two patients, one with nonsense mutation (p.R2434*) and the other had a large deletion spanning exons 16–52.

Conclusion

The molecular pathology of a large cohort of Indian VWD patients could be identified using a combination of techniques. A wide heterogeneity was observed in the nature of mutations in Indian VWD patients.

Prenatal diagnosis in severe von Willebrand disease families from India using combination of phenotypic and genotypic assays

OBJECTIVE

This study aimed to offer genetic diagnosis to affected type 3 severe von Willebrand disease families.

METHOD

Thirteen families were referred for prenatal diagnosis during the first and second trimesters of pregnancy. Prenatal diagnosis was offered by chorionic villus sampling between 11 and 12 weeks and by cordocentesis between 18 and 19.5 weeks of gestation. Phenotypic analysis included FVIII:C and von Willebrand factor antigen assays. A combination of molecular biological techniques which included PCR-restriction fragment length polymorphism technique using intron 40 variable number tandem repeat (VNTR) markers, conformation sensitive gel electrophoresis, direct DNA sequencing, and multiple ligation probe amplification (MLPA) were used to offer genotyic diagnosis in the remaining families.

RESULTS

Diagnosis was offered by intron 40 VNTR analysis in eight families. In one family, the diagnosis was given by direct mutation detection technique, whereas in another diagnosis was given by MLPA technique as the index case showed the presence of large deletion within von Willebrand factor. In three families, diagnosis was offered by cordocentesis on the basis of phenotypic assays, further confirmed by genotyping.

CONCLUSION

Both first and second-trimester prenatal diagnoses could be successfully offered using a combination of phenotypic and genotypic techniques to all severe von Willebrand disease families.

von Willebrand disease: advances in pathogenetic understanding, diagnosis, and therapy

von Willebrand disease (VWD) is the most common autosomally inherited bleeding disorder. The disease represents a range of quantitative and qualitative pathologies of the adhesive glycoprotein von Willebrand factor (VWF). The pathogenic mechanisms responsible for the type 2 qualitative variants of VWF are now well characterized, with most mutations representing missense substitutions influencing VWF multimer structure and interactions with platelet GPIbα and collagen and with factor VIII. The molecular pathology of type 3 VWD has been similarly well characterized, with an array of different mutation types producing either a null phenotype or the production of VWF that is not secreted. In contrast, the pathogenetic mechanisms responsible for type 1 VWD remain only partially resolved. In the hemostasis laboratory, the measurement of VWF:Ag and VWF:RCo are key components in the diagnostic algorithm for VWD, although the introduction of direct GPIbα-binding assays may become the functional assay of choice. Molecular genetic testing can provide additional benefit, but its utility is currently limited to type 2 and 3 VWD. The treatment of bleeding in VWD involves the use of desmopressin and plasma-derived VWF concentrates and a variety of adjunctive agents. Finally, a new recombinant VWF concentrate has just completed clinical trial evaluation and has demonstrated excellent hemostatic efficacy and safety.

Inherited abnormalities of coagulation: hemophilia, von Willebrand disease, and beyond

Bleeding disorders are broadly classified into primary and secondary hemostatic defects. Primary hemostatic disorders (disorders of platelets and von Willebrand factor) mainly result in mucocutaneous bleeding symptoms such as epistaxis, menorrhagia, petechiae, easy bruising, and bleeding after dental and surgical interventions. Secondary hemostatic disorders (congenital or acquired deficiencies of coagulation factors) typically manifest with delayed, deep bleeding into muscles and joints. This article provides a generalized overview of the pathophysiology, clinical manifestations, laboratory abnormalities, and molecular basis of inherited abnormalities of coagulation with a focus on hemophilia, von Willebrand disease, and rare inherited coagulation disorders.

von Willebrand disease: advances in pathogenetic understanding, diagnosis, and therapy

von Willebrand disease (VWD) is the most common autosomally inherited bleeding disorder. The disease represents a range of quantitative and qualitative pathologies of the adhesive glycoprotein von Willebrand factor (VWF). The pathogenic mechanisms responsible for the type 2 qualitative variants of VWF are now well characterized, with most mutations representing missense substitutions influencing VWF multimer structure and interactions with platelet GPIbα and collagen and with factor VIII. The molecular pathology of type 3 VWD has been similarly well characterized, with an array of different mutation types producing either a null phenotype or the production of VWF that is not secreted. In contrast, the pathogenetic mechanisms responsible for type 1 VWD remain only partially resolved. In the hemostasis laboratory, the measurement of VWF:Ag and VWF:RCo are key components in the diagnostic algorithm for VWD, although the introduction of direct GPIbα-binding assays may become the functional assay of choice. Molecular genetic testing can provide additional benefit, but its utility is currently limited to type 2 and 3 VWD. The treatment of bleeding in VWD involves the use of desmopressin and plasma-derived VWF concentrates and a variety of adjunctive agents. Finally, a new recombinant VWF concentrate has just completed clinical trial evaluation and has demonstrated excellent hemostatic efficacy and safety.

Malposition and expulsion of the levonorgestrel intrauterine system among women with inherited bleeding disorders

The levonorgestrel-releasing intrauterine system (LNG-IUS) is indicated for the management of menorrhagia and for contraception. The LNG-IUS is effective at reducing menstrual bleeding and improving haemoglobin among women with bleeding disorders. Expulsion rates for the LNG-IUS among normal women are reported to be approximately 5-10%. The aim of this study was to examine the malposition and expulsion rates of the LNG-IUS among women with inherited bleeding disorders. We conducted a retrospective study of women with an inherited bleeding disorder in Kingston, Canada treated with an LNG-IUS between May 2005 and June 2012. The primary outcome was a combined endpoint of expulsion and/or malposition. Predetermined secondary outcomes were patient satisfaction and changes in haemoglobin and ferritin levels. The median age of the women at the time of LNG-IUS insertion was 31 years (range 18-43, mean 32.1 years). The most common diagnosis was type 1 VWD (12/20, 60%). There were three LNG-IUS expulsions and two episodes of device malposition resulting in removal [5/20 (25.0%), 95% CI 11.2-46.9%]. An additional five women had their device removed prematurely. The overall proportion of devices resulting in discontinuation in this population was 10/20 (50.0%, 95% CI 29.9-70.1%). In this retrospective study, a significant proportion of women with an inherited bleeding disorder had an LGN-IUS removed due to poor patient satisfaction, malposition, or expulsion. Further studies into the causes of higher complication rates and interventions such as premedication or prolonged treatment with antifibrinolytic agents targeted at improving outcomes in this population are required.

Quantification of perioperative changes in von Willebrand factor and factor VIII during elective orthopaedic surgery in normal individuals

von Willebrand's disease (VWD) patients undergoing major surgery are prophylactically treated to promote haemostasis. There is variability in perioperative clinical practice; however, most guidelines suggest replacing the deficient factor to a level of 1.0 IU mL(-1) (or 100%). A review of the literature reveals a paucity of well constructed descriptive data quantifying the changes in coagulation that occur in response to surgical stress. The aim of this study was to quantify the changes in haemostatic variables occurring in response to elective orthopaedic surgery in normal individuals. Eligible subjects >18 years of age undergoing total hip or knee replacement were recruited. Blood samples were drawn at five time points: baseline, preoperatively, 30 min after surgical incision, 30 min postoperatively, postoperative day (POD) 1. Analyses included t-tests and repeated measures anova. Overall 30 patients, 21 women and 9 men, with a mean age of 65 were included in the final analysis. All von Willebrand factor (VWF) variables were seen to significantly decrease intraoperatively and increase postoperatively. VWF multimers showed a statistically significant decrease in high molecular weight multimers intraoperatively and an increase postoperatively. On subgroup analysis, age, gender and anaesthesia type were significantly correlated with changes in VWF parameters. Data presented in the current study establish a physiological baseline for VWF parameters in the normal population and demonstrate mean VWF/factor VIII levels greater than 1.0 IU mL(-1) intraoperatively. As such, current management in VWD patients does not appear to mimic the normal physiological response to surgery.

The genetics of Canadian type 3 von Willebrand disease: further evidence for co-dominant inheritance of mutant alleles

BACKGROUND

Type 3 von Willebrand disease (VWD) is the most severe form of the disease and is classically inherited in an autosomal recessive fashion.

OBJECTIVES

The aim of the current study was to investigate the molecular pathogenesis of a Canadian cohort of type 3 VWD patients.

PATIENTS AND METHODS

Thirty-four families comprised of 100 individuals were investigated. Phenotypic data, including bleeding scores (BS), von Willebrand factor (VWF) laboratory values and anti-VWF inhibitor status were included as well as sequence analysis.

RESULTS

We identified 31 different mutations (20 novel): 8 frameshift, 5 splice site, 9 nonsense, 1 gene conversion, 6 missense and 2 partial gene deletion mutations. The majority of mutations identified were in the propeptide (42%); index cases (IC) with these mutations exhibited more severe bleeding (BS = 22) than those with mutations elsewhere in VWF (BS = 13). Sixty-two out of 68 (91%) mutant alleles were identified. Twenty-nine IC (85%) had a VWF null genotype identified; 17 homozygous, 12 compound heterozygous. In five IC (15%), two mutant VWF alleles were not identified to explain the type 3 VWD phenotype. In four ICs only one mutant VWF allele was identified and in one IC no mutant VWF alleles were identified.

CONCLUSIONS

We have investigated the molecular pathogenesis of a Canadian cohort of type 3 VWD patients. Obligate carriers are not phenotypically silent in the Canadian population; 48% have been diagnosed with type 1 VWD. In approximately 50% of families in this study the inheritance pattern for type 3 VWD is co-dominant and not recessive.

Alloantibodies in von Willebrand disease

The development of alloantibodies against von Willebrand factor (VWF) represents a rare but serious complication of treatment of von Willebrand disease (VWD), occurring in ~5% to 10% of type 3 VWD patients. Affected patients can present with a range of symptoms, including lack or loss of hemostatic response to infused VWF concentrates up to anaphylactic reactions in rare cases. It is classically reported in multitransfused patients and occurs most frequently in patients with partial or complete VWF gene deletions. A positive family history of anti-VWF antibodies also appears to be a risk factor. There is a lack of standardization of laboratory methods for antibody identification and characterization. Issues of variability in laboratory approaches as well as the rarity of the complication act as a barrier to future studies. Recombinant factor VIII as well as bypassing agents and immune tolerance have been reported as effective treatments; however, aside from case reports, little exists in the literature to guide management. The imminent clinical availability of recombinant VWF has prompted a resurgence of interest in this area. Additional study is warranted to address the deficiencies in our understanding of this treatment complication.

Establishment and characterization of a new and stable collagen-binding assay for the assessment of von Willebrand factor activity

Introduction

Laboratory diagnosis of von Willebrand disease (VWD) requires determination of both von Willebrand factor (VWF) protein levels and activity. Current VWF activity tests include the ristocetin cofactor assay and the collagen-binding assay (VWF:CB). The goal of this investigation is to characterize a new collagen-binding assay and to determine its effectiveness in identifying VWD.

Methods

Analytical studies were carried out to characterize the performance of a new VWF:CB ELISA. Additionally, samples from a normal population were tested as were well-characterized type 1 and type 2 VWD samples.

Results

Repeatability and within-laboratory precision studies resulted in coefficients of variation (CVs) of ≤11%. A linear range of 1–354% (0.01–3.54 IU/mL) was determined, along with a limit of detection and a lower limit of quantitation of 1.6% and 4.0% (0.016 and 0.04 IU/mL), respectively. Samples tested from apparently healthy individuals resulted in a normal range of 54–217% (0.54–2.17 IU/mL). Known VWD type 1 and type 2 samples were also analyzed by the ELISA, with 99% of samples having VWF:CB below the normal reference range and an estimated 96% sensitivity and 87% specificity using a VWF collagen-binding/antigen cutoff ratio of 0.50.

Conclusion

This new VWF:CB ELISA provides an accurate measure of collagen-binding activity that aids in the diagnosis and differentiation of type 1 from type 2 VWD.

Why is my patient bleeding or bruising?

The evaluation of a patient presenting with bleeding symptoms is challenging. Bleeding symptoms are frequently reported by a normal population, and overlap significantly with bleeding disorders, such as type 1 Von Willebrand disease. The history is subjective; bleeding assessment tools significantly facilitate an accurate quantification of bleeding severity. The differential diagnosis is broad, ranging from defects in primary hemostasis, coagulation deficiencies, to connective tissue disorders. Finally, despite significant clinical evidence of abnormal bleeding, many patients will have not an identifiable disorder. Clinical management of bleeding disorders is highly individualized and focuses on the particular symptoms experienced by the patient.

Validation of an automated latex particle-enhanced immunoturbidimetric von Willebrand factor activity assay

BACKGROUND

Laboratory diagnosis of von Willebrand disease (VWD) requires accurate measurement of plasma von Willebrand factor (VWF) activity.

OBJECTIVES

To evaluate laboratory characteristics, diagnostic accuracy and testing utilities of an automated latex particle-enhanced immunoturbidimetric VWF assay (VWF:Lx) based on a monoclonal antibody recognizing the VWF-platelet glycoprotein (GP) Ib binding domain.

METHODS

Laboratory characteristics including lower detection limit, linearity, precision, sample stability, and method comparison between VWF:Lx and VWF ristocetin cofactor activity by platelet aggregometry (VWF:RCo) were examined. To assess VWF:Lx diagnostic accuracy, 492 patient plasma samples, including 40 previously characterized VWD patient samples, were tested for VWF antigen (VWF:Ag) and VWF:RCo by either aggregometry or flow cytometry, and VWF:Lx with supplemental VWF multimer analysis when indicated. Based on results of VWF:Ag, VWF:RCo and VWF multimer analysis, and available clinical information, samples were categorized as: normal; VWD types 1, 2A/B, 2M, or severe 1 vs. 2M; or acquired VWF abnormalities (AVWA) due to subtle loss of highest molecular weight multimers.

RESULTS

VWF:Lx had excellent laboratory characteristics and linear correlation with VWF:RCo (R(2) = 0.93). VWF:Lx accurately classified virtually all normal and VWD patient samples. Compared with VWF:RCo, VWF:Lx had superior sensitivity and specificity for distinguishing severe type 1 vs. 2M VWD and identifying AVWA. A proposed screening panel comprising VWF:Ag and VWF:Lx had 100% and 83% sensitivity for detecting VWD and AVWA, respectively.

CONCLUSIONS

VWF:Lx has excellent laboratory characteristics and diagnostic accuracy compared with VWF:RCo, and can be used as part of an initial VWD screening panel and as a supplementary test.

von Willebrand disease in the pediatric and adolescent population

Recent studies indicate that bleeding disorders, particularly von Willebrand disease (VWD) is more prevalent than previously thought in adolescents with menorrhagia. Menorrhagia management in undiagnosed disorders of hemostasis may be associated with unwanted risks and complications. The prevalence of symptomatic VWD in the pediatric primary care setting appears to be 0.11% (95% CI, 0.04-0.25%). Studies evaluating the prevalence of VWD in adolescents with menorrhagia have included over 500 patients with a prevalence range from 3 to 36% depending on the clinical setting studied, with the highest prevalence seen in adolescents referred to an outpatient Hemophilia Center, while the lowest prevalence is seen in the acute hospital setting. Recently, the diagnosis of VWD has been facilitated by the use of pediatric bleeding questionnaires that have proved useful in quantifying the severity of bleeding symptoms. Treatment of VWD is often complex because a combination of therapies is often required. Potential treatment options include estrogen-progesterone preparations, desmopressin, antifibrinolytic agents and von Willebrand factor concentrates. More research is needed to evaluate the effectiveness of the various treatment modalities in the adolescent population.

A prospective evaluation of the prevalence of symptomatic von Willebrand disease (VWD) in a pediatric primary care population

The prevalence of von Willebrand disease (VWD) is reported as approximately 1%; however, these estimates were not based on individuals with significant symptoms. Four thousand five hundred ninety-two unselected parents/children were asked: "Does your child have a problem with bleeding/bruising?"; 223 (5%) answered yes, 41 of whom were administered the validated Pediatric Bleeding Questionnaire and had VWF testing. Five were diagnosed with VWD (three type 1, one type 2A, one type 2B). The prevalence of bleeding/bruising in a general pediatric population is 5%; the prevalence of symptomatic VWD at the level of pediatric primary care is at least 1 in 1,000.