Different bleeding risk in type 2A and 2M von Willebrand disease: a 2-year prospective study in 107 patients

The Influence of Hypothyroid Metabolic Status on Blood Coagulation and the Acquired von Willebrand Syndrome

The intent of this prospective study aimed to identify the influence of hypothyroid metabolic status on the coagulation and fibrinolytic system and association with the acquired von Willebrand syndrome (VWS-ac). We compared 54 patients without substitution therapy after radical thyroidectomy with 58 control subjects without pathological thyroid-stimulating-hormone (TSH)-values. Patients with TSH > 17.5 mU/L over a period of >4 weeks were included. The control-collective was selected based on age and sex to match the patient-collective. The data were collected using laboratory coagulation tests and patient questionnaires; a bleeding score was determined. There were significant differences in the measurement of activated-partial-thromboplastin-time (aPTT/p = 0.009), coagulation-factor VIII (p < 0.001) and von-Willebrand-activity (VWF-ac/p = 0.004) between the patient and control groups. The patient cohort showed an increased aPTT and decreased factor VIII and VWF-ac. 29.7% of the patient-collective compared to 17.2% of the control subjects met the definition of VWS-Ac (p = 0.12). The bleeding score showed significantly more bleeding symptoms in patients with a laboratory constellation of VWS-ac (no family history; p = 0.04). Our results suggest hypocoagulability in hypothyroid patients. Hypothyroidism appears to have a higher incidence of VWS-ac. The increased risk of bleeding complications in hypothyroid patients may be of relevant importance for the outcome, especially in the context of invasive interventions.

Laboratory diagnosis of von Willebrand disease in the age of the new guidelines: considerations based on geography and resources

von Willebrand disease (VWD) is considered the most common bleeding disorder and arises from deficiency and/or defect in the adhesive plasma protein von Willebrand factor (VWF). Diagnosis of VWD requires clinical assessment and is facilitated by laboratory testing. Several guidelines for VWD diagnosis exist, with the latest American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia 2021 guidelines presenting 11 recommendations, some of which have drawn controversy. In the current narrative review, we provide additional context around difficulties in laboratory diagnosis/exclusion/typing of VWD, with a focus on developing countries/resource-poor settings. In particular, there are many variations in assay methodology, and some methods express high assay variability and poor low-level VWF sensitivity that compromises their utility. Although we favor an initial 4-test assay panel, comprising factor (F) VIII coagulant activity, VWF antigen, VWF glycoprotein Ib binding (VWF:GPIbR or VWF:GPIbM favored over VWF Ristocetin cofactor) and VWF collagen binding, we also provide strategies for laboratories only able to incorporate an initial 3-test assay panel, as favored by the latest guidelines, to improve diagnostic accuracy.

Gastrointestinal bleeding in von Willebrand patients: special diagnostic and management considerations

INTRODUCTION

Severe and recurrent gastrointestinal (GI) bleeding caused by angiodysplasia is a significant problem in patients with von Willebrand disease (VWD) and in those with acquired von Willebrand syndrome (AVWS). At present, angiodysplasia-related GI bleeding is often refractory to standard treatment including replacement therapy with von Willebrand factor (VWF) concentrates and continues to remain a major challenge and cause of significant morbidity in patients despite advances in diagnostics and therapeutics.

AREAS COVERED

This paper reviews the available literature on GI bleeding in VWD patients, examines the molecular mechanisms implicated in angiodysplasia-related GI bleeding, and summarizes existing strategies in the management of bleeding GI angiodysplasia in patients with VWF abnormalities. Suggestions are made for further research directions.

EXPERT OPINION

Bleeding from angiodysplasia poses a significant challenge for individuals with abnormal VWF. Diagnosis remains a challenge and may require multiple radiologic and endoscopic investigations. Additionally, there is a need for enhanced understanding at a molecular level to identify effective therapies. Future studies of VWF replacement therapies using newer formulations as well as other adjunctive treatments to prevent and treat bleeding will hopefully improve care.

Low von Willebrand Disease: A Bleeding Disorder of Unknown Cause?

von Willebrand disease (VWD) represents the most common inherited bleeding disorder. The majority of VWD cases are characterized by partial quantitative reductions in plasma von Willebrand factor (VWF) levels. Management of patients with mild to moderate VWF reductions in the range of 30 to 50 IU/dL poses a common clinical challenge. Some of these low VWF patients present with significant bleeding problems. In particular, heavy menstrual bleeding and postpartum hemorrhage can cause significant morbidity. Conversely, however, many individuals with mild plasma VWF:Ag reductions do not have any bleeding sequelae. In contrast to type 1 VWD, most patients with low VWF do not have detectable pathogenic VWF sequence variants, and bleeding phenotype correlates poorly with residual VWF levels. These observations suggest that low VWF is a complex disorder caused by variants in other genes beyond VWF. With respect to low VWF pathobiology, recent studies have shown that reduced VWF biosynthesis within endothelial cells likely plays a key role. However, pathological enhanced VWF clearance from plasma has also been described in approximately 20% of low VWF cases. For low VWF patients who require hemostatic treatment prior to elective procedures, tranexamic acid and desmopressin have both been shown to be efficacious. In this article, we review the current state of the art regarding low VWF. In addition, we consider how low VWF represents an entity that appears to fall between type 1 VWD on the one hand and bleeding disorders of unknown cause on the other.

Special considerations in GI bleeding in VWD patients

Gastrointestinal (GI) bleeding is an important cause of morbidity and mortality in von Willebrand disease (VWD). It has been noted that GI bleeding caused by angiodysplasia is overrepresented in VWD patients compared to other causes. The bleeding from angiodysplasia is notoriously difficult to treat; recurrences and rebleeds are common. A growing body of basic science evidence demonstrates that von Willebrand factor negatively regulates angiogenesis through multiple pathways. VWD is clinically highly associated with angiodysplasia. The predisposition to angiodysplasia likely accounts for many of the clinical difficulties related to managing GI bleeding in VWD patients. Diagnosis and treatment are challenging with the current tools available, and much further research is needed to further optimize care for these patients with regard to acute treatment, prophylaxis, and adjunctive therapies. In this review we provide an overview of the available literature on GI bleeding in VWD and explore the molecular underpinnings of angiodysplasia-related GI bleeding. Considerations for diagnostic effectiveness are discussed, as well as the natural history and recurrence of these lesions and which therapeutic options are available for acute and prophylactic management.

Analysis of von Willebrand Disease in the "Heart of Europe"

Background  von Willebrand disease (VWD) is a genetic bleeding disorder caused by defects of von Willebrand factor (VWF), quantitative (type 1 and 3) or qualitative (type 2). The laboratory phenotyping is heterogenic making diagnosis difficult.

Objectives  Complete laboratory analysis of VWD as an expansion of the previously reported cross-sectional family-based VWD study in the Czech Republic (BRNO-VWD) and Slovakia (BRA-VWD) under the name “Heart of Europe,” in order to improve the understanding of laboratory phenotype/genotype correlation.

Patients and Methods  In total, 227 suspected VWD patients were identified from historical records. Complete laboratory analysis was established using all available assays, including VWF multimers and genetic analysis.

Results  A total of 191 patients (from 119 families) were confirmed as having VWD. The majority was characterized as a type 1 VWD, followed by type 2. Multimeric patterns concordant with laboratory phenotypes were found in approximately 83% of all cases. A phenotype/genotype correlation was present in 84% (77% type 1, 99% type 2, and 61% type 3) of all patients. Another 45 candidate mutations (23 novel variations), not found in the initial study, could be identified (missense 75% and truncating 24%). An exon 1–3 gene deletion was identified in 14 patients where no mutation was found by direct DNA sequencing, increasing the linkage up to 92%, overall.

Conclusion  This study provides a cross-sectional overview of the VWD population in a part of Central Europe. It is an addition to the previously published BRNO-VWD study, and provides important data to the International Society of Thrombosis and Haemostasis/European Association for Haemophilia and Allied Disorders VWD mutation database with identification of novel causal mutations.

Impact of hepatopulmonary syndrome in liver transplantation candidates and the role of angiogenesis

BACKGROUND

Hepatopulmonary syndrome affects 10-30% of patients with cirrhosis and portal hypertension. We evaluated the serum angiogenic profile of hepatopulmonary syndrome and assessed the clinical impact of hepatopulmonary syndrome in patients evaluated for liver transplantation.

METHODS

The Pulmonary Vascular Complications of Liver Disease 2 study was a multicentre, prospective cohort study of adults undergoing their first liver transplantation evaluation. Hepatopulmonary syndrome was defined as an alveolar-arterial oxygen gradient ≥15 mmHg (≥20 mmHg if age >64 years), positive contrast-enhanced transthoracic echocardiography and absence of lung disease.

RESULTS

We included 85 patients with hepatopulmonary syndrome and 146 patients without hepatopulmonary syndrome. Patients with hepatopulmonary syndrome had more complications of portal hypertension and slightly higher Model for End-Stage Liver Disease-Na score compared to those without hepatopulmonary syndrome (median (interquartile range) 15 (12-19) versus 14 (10-17), p=0.006). Hepatopulmonary syndrome patients had significantly lower 6-min walk distance and worse functional class. Hepatopulmonary syndrome patients had higher circulating angiopoietin 2, Tie2, tenascin C, tyrosine protein kinase Kit (c-Kit), vascular cell adhesion molecule 1 and von Willebrand factor levels, and lower E-selectin levels. Patients with hepatopulmonary syndrome had an increased risk of death (hazard ratio 1.80, 95% CI 1.03-3.16, p=0.04), which persisted despite adjustment for covariates (hazard ratio 1.79, 95% CI 1.02-3.15, p=0.04). This association did not vary based on levels of oxygenation, reflecting the severity of hepatopulmonary syndrome.

CONCLUSION

Hepatopulmonary syndrome was associated with a profile of abnormal systemic angiogenesis, worse exercise and functional capacity, and an overall increased risk of death.

Outcomes of long-term von Willebrand factor prophylaxis use in von Willebrand disease: A systematic literature review

BACKGROUND

Von Willebrand Disease (VWD) is a common inherited bleeding disorder. Patients with VWD suffering from severe bleeding may benefit from the use of secondary long-term prophylaxis.

AIM

Systematically summarize the evidence on the clinical outcomes of secondary long-term prophylaxis in patients with VWD and severe recurrent bleedings.

METHODS

We searched Medline and EMBASE through October 2019 for relevant randomized clinical trials (RCTs) and comparative observational studies (OS) assessing the effects of secondary long-term prophylaxis in patients with VWD. We used Cochrane Risk of Bias (RoB) tool and the RoB for Non-Randomized Studies of interventions (ROBINS-I) tool to assess the quality of the included studies. We conducted random-effects meta-analyses and assessed the certainty of the evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

We included 12 studies. Evidence from one placebo controlled RCT suggested that VWD prophylaxis as compared to no prophylaxis reduced the rate of bleeding episodes (Rate ratio [RR], .24; 95% confidence interval [CI], .17-.35; low certainty evidence), and of epistaxis (RR, .38; 95%CI, .21-.67; moderate certainty evidence), and may increase serious adverse events RR 2.73 (95%CI .12-59.57; low certainty). Evidence from four before-and-after studies in which researchers reported comparative data suggested that VWD prophylaxis reduced the rate of bleeding (RR .34; 95%CI, .25-.46; very low certainty evidence).

CONCLUSION

VWD prophylaxis treatment seems to reduce the risk of spontaneous bleeding, epistaxis, and hospitalizations. More RCTs should be conducted to increase the certainty in these benefits.

Von Willebrand disease type 2M: Correlation between genotype and phenotype

BACKGROUND

An appropriate clinical diagnosis of von Willebrand disease (VWD) can be challenging because of a variable bleeding pattern and laboratory phenotype. Genotyping is a powerful diagnostic tool and may have an essential role in the diagnostic field of VWD.

OBJECTIVES

To unravel the clinical and laboratory heterogeneity of genetically confirmed VWD type 2M patients and to investigate their relationship.

METHODS

Patients with a confirmed VWD type 2M genetic variant in the A1 or A3 domain of von Willebrand factor (VWF) and normal or only slightly aberrant VWF multimers were selected from all subjects genotyped at the Radboud university medical center because of a high suspicion of VWD. Bleeding scores and laboratory results were analyzed.

RESULTS

Fifty patients had a clinically relevant genetic variant in the A1 domain. Median bleeding score was 5. Compared with the nationwide Willebrand in the Netherlands study type 2 cohort, bleeding after surgery or delivery was reported more frequently and mucocutaneous bleedings less frequently. Median VWF activity/VWF antigen (VWF:Act/VWF:Ag) ratio was 0.32, whereas VWF collagen binding activity/VWF antigen (VWF:CB/VWF:Ag) ratio was 0.80. Variants in the A3 domain were only found in two patients with low to normal VWF:Act/VWF:Ag ratios (0.45, 1.03) and low VWF:CB/VWF:Ag ratios (0.45, 0.63).

CONCLUSION

Genetically confirmed VWD type 2M patients have a relatively mild clinical phenotype, except for bleeding after surgery and delivery. Laboratory phenotype is variable and depends on the underlying genetic variant. Addition of genotyping to the current phenotypic characterization may improve diagnosis and classification of VWD.

Gastrointestinal Bleeding in Congenital Bleeding Disorders

Gastrointestinal bleeding (GIB) is serious, intractable, and potentially life-threatening condition. There is considerable heterogeneity in GIB phenotypes among congenital bleeding disorders (CBDs), making GIB difficult to manage. Although GIB is rarely encountered in CBDs, its severity in some patients makes the need for a comprehensive and precise assessment of underlying factors and management approaches imperative. Initial evaluation of GIB begins with assessment of hematological status; GIB should be ruled out in patients with chronic anemia, and in presentations that include hematemesis, hematochezia, or melena. High-risk patients with recurrent GIB require urgent interventions such as replacement therapy for treatment of coagulation factor deficiency (CFD). However, the best management strategy for CFD-related bleeding remains controversial. While several investigations have identified CBDs as potential risk factors for GIB, research has focused on assessing the risks for individual factor deficiencies and other CBDs. This review highlights recent findings on the prevalence, management strategies, and alternative therapies of GIB related to CFDs, and platelet disorders.

Bleeding patterns in patients before and after diagnosis of von Willebrand disease: Analysis of a US medical claims database

Introduction

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. The bleeding phenotype is variable, and some individuals have persistent symptoms post‐diagnosis.

Aim

To characterize bleeding patterns in patients with VWD before and after diagnosis.

Methods

De‐identified claims data for commercially insured patients in the IQVIA PharMetrics® Plus US database (Jan‐2006 to Jun‐2015) were extracted. Eligible patients had ≥2 claims for VWD (ICD‐9 code 286.4), and continuous health‐plan enrolment for ≥2 years before and after diagnosis. Bleeding event, treatment and treating‐physician type were analysed for 18 months before and 7‐24 months after diagnosis, according to pre‐diagnosis bleeding phenotype (claims from one vs multiple bleed sites) and post‐diagnosis bleeding status (resolved [no post‐diagnosis bleed claims] vs continued [≥1 claim]).

Results

Data for 3756 eligible patients (72.6% female; 71.0% aged ≥18 years at diagnosis) were analysed. Overall, 642 (17.1%) and 805 (21.4%) patients had single‐ and multiple‐site bleed claims pre‐diagnosis, respectively, and 1263 (33.6%) patients (38.5% of women, 20.8% of men) continued to bleed post‐diagnosis. Multiple‐site bleeding was associated with pre‐diagnosis heavy menstrual bleeding (HMB), oral contraceptive (OC) use and nasal cauterization. Continued bleeding post‐diagnosis was associated with pre‐diagnosis gastrointestinal bleeding, HMB and epistaxis; pre‐diagnosis use of OCs, aminocaproic acid and nasal cauterization; and younger age at diagnosis. Few patients consulted a haematologist for bleed management.

Conclusion

Many patients with VWD have persistent bleeding from multiple sites and continue to bleed post‐diagnosis. Our findings suggest a need to optimize management to reduce the symptomatic burden of VWD following diagnosis.

Vascular abnormalities in patients with von Willebrand disease: A scoping review

BACKGROUND

Qualitative or quantitative defects of von Willebrand factor (VWF) such as in von Willebrand disease (VWD) are associated with vascular abnormalities, especially in the gastrointestinal (GI) tract. However, the locations, extent, and natural history of vascular abnormalities in patients with VWD is not well understood. To summarize the existing literature on the topic, we conducted a scoping review of vascular abnormalities in patients with VWD.

METHODS

We searched MEDLINE and EMBASE from inception to September 1, 2020, for studies clinically describing vascular abnormalities in VWD patients. Screening and data extraction was completed independently and in duplicate and each abnormality was documented individually.

RESULTS

After screening, 54 studies that reported patient level data comprising 146 patients were included. Type 2A (39%) and type 3 (14.4%) were the most common VWD subtypes. The most common site of vascular malformation was the GI tract, occurring in 124 patients (84.9%), whereas 18 (12.3%) had non-GI vascular abnormalities and 4 (2.7%) had both GI and non-GI vascular abnormalities. With respect to outcomes, the clinical course was not specified in the majority (55.5%) of patients. Survey and population level data were reported in nine studies, demonstrating vascular abnormalities occurred at higher rates in VWD and that VWD patients are overrepresented among those with those abnormalities.

CONCLUSION

Vascular malformations in patients with VWD occur primarily in the gastrointestinal tract. Type 2A and type 3 VWD are the most common subtypes affected. The clinical treatment and natural history of these abnormalities remains understudied and further research is needed.

Genotypes of European and Iranian patients with type 3 von Willebrand disease enrolled in 3WINTERS-IPS

Type 3 von Willebrand disease (VWD3) is a rare and severe bleeding disorder characterized by often undetectable von Willebrand factor (VWF) plasma levels, a recessive inheritance pattern, and heterogeneous genotype. The objective of this study was to identify the VWF defects in 265 European and Iranian patients with VWD3 enrolled in 3WINTERS-IPS (Type 3 Von Willebrand International Registries Inhibitor Prospective Study). All analyses were performed in centralized laboratories. The VWF genotype was studied in 231 patients with available DNA (121 [115 families] from Europe [EU], and 110 [91 families] from Iran [IR]). Among 206 unrelated patients, 134 were homozygous (EU/IR = 57/77) and 50 were compound heterozygous (EU/IR = 43/7) for VWF variants. In 22 patients, no or only one variant was found. A total of 154 different VWF variants (EU/IR = 101/58 [5 shared]) were identified among the 379 affected alleles (EU/IR = 210/169), of which 48 (EU/IR = 18/30) were novel. The variants p.Arg1659*, p.Arg1853*, p.Arg2535*, p.Cys275Ser, and delEx1_Ex5 were found in both European and Iranian VWD3 patients. Sixty variants were identified only in a single allele (EU/IR = 50/10), whereas 18 were recurrent (≥3 patients) within 144 affected alleles. Nine large deletions and one large insertion were found. Although most variants predicted null alleles, 21% of patients carried at least 1 missense variant. VWD3 genotype was more heterogeneous in the European population than in the Iranian population, with nearly twice as many different variants. A higher number of novel variants were found in the Iranian VWD3 patients.

Type 2A and 2M von Willebrand Disease: Differences in Phenotypic Parameters According to the Affected Domain by Disease-Causing Variants and Assessment of Pathophysiological Mechanisms

Type 2A and 2M von Willebrand disease (VWD) broadly show similar phenotypic parameters, but involve different pathophysiological mechanisms. This report presents the clinical and laboratory profiles of type 2A and type 2M patients genotypically diagnosed at one large center. Higher bleeding score values and a higher incidence of major bleeding episodes were observed in type 2A compared with type 2M, potentially reflective of the absence of large and intermediate von Willebrand factor (VWF) multimers in 2A. In type 2A, most of disease-causing variants (DCVs) appeared to be responsible for increased VWF clearance and DCV clustered in the VWF-A1 domain resulted in more severe clinical profiles. In type 2M, DCV in the VWF-A1 domain showed different laboratory patterns, related to either reduced synthesis or shortened VWF survival, and DCV in the VWF-A2 domain showed patterns related mainly to shortened survival. VWF-type 1 collagen binding/Ag (C1B/Ag) showed different patterns according to DCV location: in type 2A VWD, C1B/Ag was much lower when DCVs were located in the VWF-A2 domain. In type 2M with DCV in the VWF-A1domain, C1B/Ag was normal, but with DCV in the VWF-A2 domain, C1B/Ag was low. The higher frequency of major bleeding in VWD 2M patients with DCV in the VWF-A2 domain than that with DCV in the VWF-A1 domain could be a summative effect of abnormal C1B/Ag, on top of the reduced VWF-GPIb binding. In silico modeling suggests that DCV impairing the VWF-A2 domain somehow modulates collagen binding to the VWF-A3 domain. Concomitant normal FVIII:C/Ag and VWFpp/Ag, mainly in type 2M VWD, suggest that other nonidentified pathophysiological mechanisms, neither related to synthesis/retention nor survival of VWF, would be responsible for the presenting phenotype.

von Willebrand factor binding to myosin assists in coagulation

von Willebrand factor (VWF) binds to platelets and collagen as a means of facilitating coagulation at sites of injury. Recent evidence has shown that myosin can serve as a surface for thrombin generation and binds to activated factor V and factor X. We studied whether VWF can also bind myosin as a means of bringing factor VIII (FVIII) to sites of clot formation. A myosin-binding assay was developed using skeletal muscle myosin to measure VWF binding, and plasma-derived and recombinant VWF containing molecular disruptions at key VWF sites were tested. Competition assays were performed using anti-VWF antibodies. FVIII binding to myosin was measured using a chromogenic FVIII substrate. Thrombin generation was measured using a fluorogenic substrate with and without myosin. Wild-type recombinant VWF and human plasma VWF from healthy controls bound myosin, whereas plasma lacking VWF exhibited no detectable myosin binding. Binding was multimer dependent and blocked by anti-VWF A1 domain antibodies or A1 domain VWF variants. The specific residues involved in myosin binding were similar, but not identical, to those required for collagen IV binding. FVIII did not bind myosin directly, but FVIII activity was detected when VWF and FVIII were bound to myosin. Myosin enhanced thrombin generation in platelet-poor plasma, although no difference was detected with the addition of myosin to platelet-rich plasma. Myosin may help to facilitate delivery of FVIII to sites of injury and indirectly accelerate thrombin generation by providing a surface for VWF binding in the setting of trauma and myosin exposure.

How I treat gastrointestinal bleeding in congenital and acquired von Willebrand disease

Gastrointestinal (GI) bleeding is distinctive of severe von Willebrand disease (VWD), generally arising in older patients; in most cases, blood transfusion and hospitalization are required. The presence of arteriovenous malformations is often described when endoscopic examinations are performed. Patients with congenital type 3, 2A, and 2B are those most frequently affected by this symptom, possibly due to the loss of high-molecular-weight multimers of von Willebrand factor (VWF). GI bleeding can also occur in patients affected by acquired von Willebrand syndrome. Endoscopic examination of the GI tract is necessary to exclude ulcers and polyps or cancer as possible causes of GI bleeding. In congenital VWD, prophylaxis with VWF/factor VIII concentrates is generally started after GI-bleeding events, but this therapy is not always successful. Iron supplementation must be prescribed to avoid chronic iron deficiency. Possible rescue therapies (high-dose statins, octreotide, thalidomide, lenalidomide, and tamoxifen) were described in a few case reports and series; however, surgery may be necessary in emergency situations or if medical treatment fails to stop bleeding. In this article, we present several clinical cases that highlight the clinical challenges of these patients and possible strategies for their long-term management.

Abnormalities in the Von Willebrand-Angiopoietin Axis Contribute to Dysregulated Angiogenesis and Angiodysplasia in Children With a Glenn Circulation

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Children with a bidirectional superior cavopulmonary connection (Glenn circulation) develop dysregulated angiogenesis and pulmonary angiodysplasia in the form of arteriovenous malformations (AVMs). No targeted therapy exists.

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The von Willebrand factor (vWF)–angiopoietin axis plays a major role in normal angiogenesis, angiodysplasia, and AVM formation in multiple diseases.

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vWF and angiopoietin-2 (which destabilizes vessel formation) were abnormal in children with a Glenn circulation versus control children. Within Glenn patients, angiopoietin-1 (which stabilizes vessel formation) and angiogenesis were different in the systemic versus pulmonary circulation. Plasma angiopoietin-1 was lower in the pulmonary circulation of Glenn patients with pulmonary AVMs than Glenn patients without AVMs.

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In parallel, differences in multiple angiogenic and inflammatory signaling peptides were observed between Glenn patients and controls, which indicated derangements in multiple angiogenic pathways in Glenn patients.

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These findings support the novel hypothesis that abnormal vWF metabolism and angiopoietin signaling dysregulate angiogenesis and contribute to pulmonary AVM formation in children with a Glenn circulation.

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The vWF-angiopoietin axis may be a target to correct angiogenic imbalance and reduce pulmonary angiodysplasia in Glenn patients.

Children with a bidirectional superior cavopulmonary (Glenn) circulation develop angiodysplasia and pulmonary arteriovenous malformations (AVMs). The von Willebrand factor (vWF)–angiopoietin axis plays a major role in AVM formation in multiple diseases. We observed derangements in global angiogenic signaling, vWF metabolism, angiopoietins, and in vitro angiogenesis in children with a Glenn circulation versus controls and within Glenn pulmonary versus systemic circulations. These findings support the novel hypothesis that abnormalities in the vWF-angiopoietin axis may dysregulate angiogenesis and contribute to Glenn pulmonary AVMs. The vWF-angiopoietin axis may be a target to correct angiogenic imbalance in Glenn patients, for whom no targeted therapy exists.

Criteria for low von Willebrand factor diagnosis and risk score to predict future bleeding

BACKGROUND

Important diagnostic and clinical aspects of moderately reduced von Willebrand factor (VWF) levels are still unknown. There is no clear evidence which cutoff value (0.50 vs 0.60 IU/ml) should be used to diagnose "low VWF." Also, the incidence of bleeding after the diagnosis has been made, and risk factors for bleeding are unknown yet.

OBJECTIVES

To investigate the incidence of postsurgical bleeding, postpartum hemorrhage (PPH), and traumatic and spontaneous bleeding after low VWF diagnosis, and to develop a risk score to predict future bleeding.

METHODS

We performed a cohort study in patients with historically lowest VWF levels of 0.31 to 0.60 IU/ml. Clinical data of patients were retrospectively collected.

RESULTS

We included 439 patients with low VWF. During a follow-up of 6.3 ± 3.7 years, 259 surgical procedures, 81 deliveries, and 109 spontaneous and traumatic bleeding episodes were reported. The incidence of postsurgical bleeding was 2.7%, whereas 10% of deliveries was complicated by PPH. Overall, 65 patients (14.8%) had bleeding requiring treatment, which was not different between patients with historically lowest VWF levels of 0.31-0.50 and 0.51-0.60 IU/ml (p = .154). Age <18 years, abnormal bleeding score at diagnosis, and being referred for bleeding symptoms at the time of diagnosis were independent risk factors for bleeding during follow-up, and therefore included in the risk score.

CONCLUSIONS

The cutoff value of low VWF diagnosis should be set at 0.60 IU/ml. Furthermore, a risk score is developed to identify individuals with a high risk for bleeding after low VWF diagnosis.

Von Willebrand Factor Multimer Densitometric Analysis: Validation of the Clinical Accuracy and Clinical Implications in Von Willebrand Disease

Von Willebrand factor (VWF) multimer analysis is important in the classification of von Willebrand disease (VWD). Current visual VWF multimer analysis is time consuming and inaccurate in detecting subtle changes in multimer patterns. Although VWF multimer densitometric analysis may be useful, the accuracy needs further investigation before it can be widely applied. In this study we aimed to validate VWF multimer densitometric analysis in a large cohort of VWD patients and to identify patient characteristics associated with densitometric outcomes. Patients were included from the Willebrand in the Netherlands (WiN) study, in which a bleeding score (BS) was obtained, and blood was drawn. For multimer analysis, citrated blood was separated on an agarose gel and visualized by Western blotting. IMAGEJ was used to generate densitometric images and medium-large VWF multimer index was calculated. We included 560 VWD patients: 328 type 1, 211 type 2, and 21 type 3 patients. Medium-large VWF multimer index performed excellent in distinguishing visually classified normal VWF multimers from reduced high-molecular-weight (HMW) multimers (area under the curve [AUC]: 0.96 [0.94-0.98], P < 0.001), normal multimers from absence of HMW multimers (AUC 1.00 [1.00-1.00], P < 0.001), and type 2A and 2B from type 2M and 2N (AUC: 0.96 [0.94-0.99], P < 0.001). Additionally, higher medium-large VWF multimer index was associated with lower BS in type 1 VWD: β = -7.6 (-13.0 to -2.1), P = 0.007, adjusted for confounders. Densitometric analysis of VWF multimers had an excellent accuracy compared with visual multimer analysis and may contribute to a better understanding of the clinical features such as the bleeding phenotype of VWD patients.

Gastrointestinal bleeding from angiodysplasia in von Willebrand disease: Improved diagnosis and outcome prediction using videocapsule on top of conventional endoscopy

BACKGROUND

Despite a high prevalence of angiodysplasia, no specific guidelines are available for the modalities of endoscopic exploration of gastrointestinal (GI) bleeding in von Willebrand disease (VWD). Whether VWD patients could benefit from video capsule endoscopy (VCE) looking for angiodysplasia eligible to endoscopic treatment or at high risk of bleeding is unknown.

OBJECTIVES

To assess the diagnostic efficacy for angiodysplasia and the prognostic value of VCE on top of conventional endoscopy in VWD patients with GI bleeding.

PATIENTS/METHODS

A survey was sent to the 30 centers of the French-network on inherited bleeding disorders to identify VWD patients referred for endoscopic exploration of GI bleeding from January 2015 to December 2017. Data obtained included patient characteristics, VWD phenotype/genotype, GI bleeding pattern, results of endoscopic investigations, and medical management applied including endoscopic therapy. We assessed by Kaplan-Meier analysis the recurrence-free survival after the first GI bleeding event according to endoscopic categorization and, in patients with angiodysplasia, to the presence of small-bowel localizations on VCE exploration.

RESULTS

GI bleeding source localization was significantly improved when including VCE exploration (P < .01), even in patients without history of angiodysplasia (P < .05). Patients with angiodysplasia had more GI bleeding recurrences (P < .01). A lower recurrence-free survival was observed in patients with angiodysplasia (log-rank test, P = .02), and especially when lesions were located in the small bowel (log-rank test, P < .01), even after endoscopic treatment with argon plasma coagulation (log-rank test, P < .01).

CONCLUSION

VCE should be more systematically used in VWD patients with unexplained or recurrent GI bleeding looking for angiodysplasia eligible to endoscopic treatment or at high risk of relapse.

Laboratory variability in the diagnosis of type 2 VWD variants

Essentials Patients with von Willebrand disease were enrolled in our study. Type 2 VWD diagnoses were based on original test results. Repeat evaluation resulted in many patients receiving a different type 2 diagnosis. Some genetic variants were particularly likely to move type 2 subcategories. ABSTRACT: Introduction Type 2 von Willebrand disease (VWD) refers to patients with a qualitative defect in von Willebrand factor. Accurate diagnosis of type 2 VWD subtypes can be challenging. Aim of the study To compare the historical diagnosis of type 2 VWD with current laboratory testing. Methods Subjects were enrolled in the Zimmerman Program either because of a preexisting diagnosis of VWD (retrospective cohort) or from evaluation for bleeding symptoms or suspected VWD (prospective cohort). Original diagnosis was assigned by the local center and central diagnosis was based on central laboratory testing. Results Two hundred and seventeen index cases in the retrospective cohort and 35 subjects in the prospective cohort carried a local diagnosis of type 2 VWD (29% and 6% of enrolled index cases, respectively). In the retrospective cohort, the diagnosis was confirmed in 66% of cases with a preexisting diagnosis of 2A, 77% 2B, 54% 2M, and 72% 2N. In the prospective cohort, 31% were confirmed 2A, 60% 2B, 23% 2M, and 100% 2N. Several genetic variants were repeatedly implicated in subjects with changed diagnosis: p.M1304R, p.R1315C, p.R1374C, and p.R1374H. Conclusions Both the prospective and retrospective cohorts demonstrated consistent variation in subjects whose diagnosis changed between 2A, 2B, and 2M. The importance of accurately diagnosing type 2 VWD may be most significant in the 2B subtype given potential concerns with the use of desmopressin in type 2B VWD. Some genetic variants appear in multiple types of VWD, making specific diagnoses challenging.

Economic burden of major bleeding events in commercially insured patients with von Willebrand disease based on claims data from the United States

BACKGROUND: von Willebrand disease (VWD) can lead to serious, life-threatening bleeding events associated with substantial clinical and economic burden. OBJECTIVE: To estimate the prevalence, health care resource utilization (HCRU), and costs associated with major bleeding events in patients with VWD. METHODS: This was a retrospective analysis of the IBM MarketScan database (2008-2016). Selected patients had ≥ 2 VWD diagnoses, no diagnosis of acquired coagulation factor deficiency, and continuous health care plan enrollment for ≥ 12 months from eligibility start date. Prevalence was calculated as the proportion of eligible patients with ≥ 1 major bleeding event during the observation period (start to end of continuous eligibility). HCRU and costs in the 12-month continuous enrollment period following the first major bleeding event were compared with those from a comparable 12-month period for patients without major bleeding events. RESULTS: Of the 19,785 patients with VWD, 15% experienced ≥ 1 major bleeding event during a median follow-up of 4 years; 89% of these events were gastrointestinal bleeds. For the economic analysis, 773 patients with ≥ 1 major bleeding event and 4,285 patients without major bleeding events met the selection criteria. Controlling for baseline covariates, patients with major bleeding events had significantly (P < 0.0001) more inpatient admissions (incidence rate ratio [IRR] = 3.2; 95% CI = 2.78-3.77), longer inpatient stays (IRR = 3.9; 95% CI = 3.12-4.93), and more emergency department visits (IRR = 2.0; 95% CI = 1.77-2.27) and outpatient visits (IRR = 1.3; 95% CI = 1.19-1.34) than patients without major bleeding events. Annual health care costs were significantly higher (P < 0.01) for patients with major bleeding events than those without them (predicted mean cost differences: total = $20,890, pharmacy = $2,593, and medical = $18,293). CONCLUSIONS: Major bleeding events were associated with increased HCRU and costs, mostly inpatient costs. Therefore, optimizing therapy to prevent or reduce major bleeding events has the potential to reduce health care use and costs in patients with VWD. DISCLOSURES: This study was funded by Baxalta U.S. Inc., a Takeda company (Lexington, MA). The study sponsor was involved with the study design, analysis, and interpretation of data; writing of the manuscript; and the decision to publish the article. Lu, Wu, and Ewenstein are employees of Baxalta U.S. Inc., a Takeda company, and are Takeda stock owners. Farahbakhshian is an employee of Shire U.S. Inc., a Takeda company, and is a Takeda stock owner. Oladapo was an employee of Baxalta U.S. Inc., a Takeda company, at the time the analysis was completed and the manuscript developed, and is a Takeda stock owner.

How we diagnose 2M von Willebrand disease (VWD): Use of a strategic algorithmic approach to distinguish 2M VWD from other VWD types

INTRODUCTION

von Willebrand disease (VWD) is the most common inherited bleeding disorder and caused by an absence, deficiency or defect in von Willebrand factor (VWF). VWD is currently classified into six different types: 1, 2A, 2B, 2N, 2M, 3. Notably, 2M VWD is more often misdiagnosed as 2A or type 1 VWD than properly identified as 2M VWD.

AIM

To describe an algorithmic approach to better ensure appropriate identification of 2M VWD, and reduce its misdiagnosis, as supported by sequential laboratory testing.

METHODS

Comparative assessment of types 1, 2A, 2B and 2M VWD using various laboratory tests, including VWF antigen and several VWF activity assays, plus DDAVP challenge data, ristocetin-induced platelet agglutination (RIPA) data, multimer analysis and genetic testing.

RESULTS

Types 1, 2A, 2B and 2M VWD give characteristic test patterns that can provisionally classify patients into particular VWD types. Notably, type 1 VWD shows low levels of VWF, but VWF functional concordance (VWF activity/Ag ratios >0.6), with both baseline assessment and post-DDAVP. Types 2A, 2B and 2M VWD show VWF functional discordance (low VWF activity/Ag ratio(s)) dependent on the defect, but type 2M separates from 2A/2B VWD based on specific test patterns, especially with collagen binding vs glycoprotein Ib binding assays. RIPA identifies 2B VWD. Multimers separate 2M from 2A/2B.

CONCLUSION

We provide strategies to improve correct diagnosis of VWD, especially focussed on 2M VWD, and which can be used by most diagnostic haemostasis laboratories, reserving genetic analysis (if required) for confirmation.

New therapies for von Willebrand disease

The management of von Willebrand disease (VWD) is based upon the dual correction of the primary hemostasis defect, due to the inherited deficiency of von Willebrand factor (VWF), and of the secondary defect of factor VIII coagulant activity (FVIII:C), due to the loss of binding and stabilization by VWF of this intrinsic coagulation factor in flowing blood. The traditional therapeutic weapons (the synthetic derivative of the antidiuretic hormone desmopressin and plasma-derived VWF/FVIII concentrates) are able to transiently correct both the defects. With the goal of tackling the primary deficiency in the disease, that is, VWF, but at the same time exploiting the normal capacity of patients to produce FVIII, the novel approach of replacing only VWF was implemented in the last 10 years. Following the manufacturing of a concentrate fractionated from human plasma and of one obtained by recombinant DNA technology, clinical studies have shown that VWF-only products correct not only the primary VWF deficiency but also the secondary FVIII:C deficiency. The demonstrated efficacy of these products in various clinical situations and, ultimately, in such a hemostasis-challenging context as surgery testifies to the effectiveness and safety of this approach. It remains to be seen whether VWF-only products are efficacious and safe in still-unexplored situations, such as use in children; the long-term use for prophylaxis; and in recurrent gastrointestinal (GI) bleeding due to angiodysplasia, a major therapeutic problem in VWD.

Successful Use of Hematopoietic Stem Cell Transplantation for 2 Pediatric Cases of Glanzmann Thrombasthenia and Review of the Literature

Glanzmann thrombasthenia is a rare platelet disorder characterized by an abnormal integrin receptor on the surface of platelets that results in the failure of platelets to aggregate. Currently, curative therapy is allogeneic hematopoietic stem cell transplantation (HSCT). The authors report 2 patients with Glanzmann thrombasthenia who successfully underwent allogeneic HSCT from unrelated donors, including one using umbilical cord blood stem cells. Although both patients had evidence of engraftment, hematopoietic recovery, and normalization of platelet aggregation, they also experienced several post-transplant complications. Allogeneic HSCT carries a significant risk of morbidity and mortality that should be considered before proceeding with the transplant.

Coexistence of Von Willebrand disease and gastrointestinal stromal tumor (G.I.S.T): Case report of a rare and challenge association

Von Willebrand disease (VWD) is the most common inherited bleeding disorder and is caused by a quantitative (type 1 and 3) or qualitative (type 2) defect of Von Willebrand factor (VWF). Bleeding from the gastrointestinal (GI) tract is not uncommon in VWD and is usually associated with angiodysplasia. We report herein on the management of a patient affected by VWD2B with severe GI bleeding secondary to gastrointestinal stromal tumor (GIST) complicated by deep vein thrombosis (DVT). The current case demonstrated that the hemostatic balance, in RBDs under specific circumstances, can range from a tendency toward a hemorrhagic to normal or prothrombotic state. In these patients, a close collaboration between hematologists and surgeons can guarantee appropriate management in high-risk clinical scenarios.

New therapies for von Willebrand disease

The management of von Willebrand disease (VWD) is based upon the dual correction of the primary hemostasis defect, due to the inherited deficiency of von Willebrand factor (VWF), and of the secondary defect of factor VIII coagulant activity (FVIII:C), due to the loss of binding and stabilization by VWF of this intrinsic coagulation factor in flowing blood. The traditional therapeutic weapons (the synthetic derivative of the antidiuretic hormone desmopressin and plasma-derived VWF/FVIII concentrates) are able to transiently correct both the defects. With the goal of tackling the primary deficiency in the disease, that is, VWF, but at the same time exploiting the normal capacity of patients to produce FVIII, the novel approach of replacing only VWF was implemented in the last 10 years. Following the manufacturing of a concentrate fractionated from human plasma and of one obtained by recombinant DNA technology, clinical studies have shown that VWF-only products correct not only the primary VWF deficiency but also the secondary FVIII:C deficiency. The demonstrated efficacy of these products in various clinical situations and, ultimately, in such a hemostasis-challenging context as surgery testifies to the effectiveness and safety of this approach. It remains to be seen whether VWF-only products are efficacious and safe in still-unexplored situations, such as use in children; the long-term use for prophylaxis; and in recurrent gastrointestinal (GI) bleeding due to angiodysplasia, a major therapeutic problem in VWD.

Updated overview on von Willebrand disease: focus on the interest of genotyping

Introduction: Von Willebrand disease (VWD) is the most common inherited bleeding disorder, characterized by a quantitative or qualitative defect of von Willebrand factor (VWF), a multimeric glycoprotein crucial for primary hemostasis and coagulation. VWD pathophysiology is heterogeneous as it includes several types and subtypes which therapeutic management is different. The mainstays of VWD treatment are desmopressin and replacement therapy based on both plasma-derived concentrates and a recently developed recombinant VWF. VWD definitive diagnosis is achieved by a battery of phenotypic biologic assays and genotyping is currently performed mostly for research.Areas covered: This narrative review will firstly present a general overview on VWD epidemiology, pathophysiology, classification, clinics, phenotypic biologic diagnosis, and treatment. Secondly, a focus on VWD genotyping will be presented with specific emphasis on the evolution of its technical aspects, its applications for research dedicated to a better understanding of VWD pathophysiology and epidemiology and its interest in both a faster diagnosis and an optimal treatment of VWD.Expert opinion: Based on analysis of the literature, it can be concluded that the fast evolution of genetic techniques together with the development of innovating treatments may significantly change diagnostic flow charts for VWD and their use for specific and personalized treatment.

Clinical and laboratory diagnosis of rare coagulation disorders (RCDs)

Rare coagulation disorders (RCDs) are a group of diseases due to coagulation factors deficiency leading to life-long bleeding diathesis. The diagnosis of RCDs is challenging due to the limited knowledge of these disorders and the large heterogeneity of their bleeding patterns. The clinical symptoms of RCDs are extremely diverse in terms of bleeding type, site, severity, age at onset, and duration. The strength of the association between clotting factor activity level in plasma and clinical symptoms is also variable within each RCD. The clinical evaluation of RCDs starts with a detailed collection of clinical history and has been facilitated by bleeding assessment tools, however their effectiveness in diagnosing RCDs requires further investigation. The following laboratory diagnosis of RCDs involves coagulation screening tests, including activated partial thromboplastin time, prothrombin time, and thrombin time. After ruling out the presence of an inhibitor by mixing studies, in case of abnormal results, the specific deficiency is identified by performing one-stage clotting assays using the specific factor-depleted plasmas as substrate. In fibrinogen and FXIII deficiencies coagulation screening tests are not informative, therefore additional tests are needed. Global assays have been developed and are thought to aid in patient management, however, they are not well standardized yet. In addition to outlining the principles of clinical and laboratory diagnosis, this review explores molecular basis of RCDs and laboratory techniques for genetic analysis, and discusses the importance and effectiveness of quality control programs to ensure standardized laboratory results.

How I manage severe von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. Most patients with mild and moderate VWD can be treated effectively with desmopressin. The management of severe VWD patients, mostly affected by type 2 and type 3 disease, can be challenging. In this article we review the current diagnosis and treatment of severe VWD patients. We will also discuss the management of severe VWD patients in specific situations, such as pregnancy, delivery, patients developing alloantibodies against von Willebrand factor and VWD patients with recurrent gastrointestinal bleeding. Moreover, we review emerging treatments that may be applied in future management of patients with severe VWD.

Variability of von Willebrand factor-related parameters in endothelial colony forming cells

Essentials Endothelial colony forming cells (ECFCs) are a powerful tool to study vascular diseases ex vivo. Separate ECFC lines show variations in morphology and von Willebrand factor-related parameters. Maximum cell density is correlated with von Willebrand factor expression in ECFCs. Variations in ECFC lines are dependent on the age and mesenchymal state of the cells. ABSTRACT: Background Endothelial colony forming cells (ECFCs) are cultured endothelial cells derived from peripheral blood. ECFCs are a powerful tool to study pathophysiological mechanisms underlying vascular diseases, including von Willebrand disease. In prior research, however, large variations between ECFC lines were observed in, among others, von Willebrand factor (VWF) expression. Objective Understand the relation between phenotypic characteristics and VWF-related parameters of healthy control ECFCs. Methods ECFC lines (n = 16) derived from six donors were studied at maximum cell density. Secreted and intracellular VWF antigen were measured by ELISA. The angiogenic capacity of ECFCs was investigated by the Matrigel tube formation assay. Differences in expression of genes involved in angiogenesis, aging, and endothelial to mesenchymal transition (EndoMT) were measured by quantitative PCR. Results Different ECFC lines show variable morphologies and cell density at maximum confluency and cell lines with a low maximum cell density show a mixed and more mesenchymal phenotype. We identified a significant positive correlation between maximum cell density and VWF production, both at protein and mRNA level. Also, significant correlations were observed between maximum cell density and several angiogenic, aging and EndoMT parameters. Conclusions We observed variations in morphology, maximum cell density, VWF production, and angiogenic potential between healthy control ECFCs. These variations seem to be attributable to differences in aging and EndoMT. Because variations correlate with cell density, we believe that ECFCs maintain a powerful tool to study vascular diseases. It is however important to compare cell lines with the same characteristics and perform experiments at maximum cell density.

Clinical and In Vitro Evidence That Left Ventricular Assist Device-Induced von Willebrand Factor Degradation Alters Angiogenesis

Background Gastrointestinal bleeding from angiodysplasia is a major problem in continuous-flow left ventricular assist device (LVAD) patients. LVAD shear stress causes pathologic degradation of VWF (von Willebrand factor). A mechanistic relationship between VWF degradation and angiodysplasia has not been explored. We tested 2 novel hypotheses: (1) clinical hypothesis: VWF fragments are elevated in LVAD patients that develop angiodysplasia and (2) in vitro hypothesis: VWF fragments generated during LVAD support alter angiogenesis, which may contribute to angiodysplasia. Methods and Results Clinical study: Paired blood samples were collected from continuous-flow LVAD patients (n=35). VWF was quantified with immunoblotting. In vitro experiments: (1) To investigate whether LVAD support alters angiogenesis, human endothelial cells were cultured with LVAD patient plasma (n=11). To investigate mechanism, endothelial cells were cultured with VWF fragments produced by exposing human VWF and ADAMTS-13 (VWF protease) to LVAD-like shear stress (175 dyne/cm², n=8). Clinical study results: in all patients (n=35, mean support 666±430 days), LVAD support degraded high-molecular-weight VWF multimers ( P<0.0001) into low-molecular-weight VWF multimers ( P<0.0001) and VWF fragments ( P<0.0001). In patients with gastrointestinal bleeding from angiodysplasia (n=7), VWF fragments were elevated ( P=0.02) versus nonbleeders. In contrast, in patients with gastrointestinal bleeding without angiodysplasia, VWF fragments were not elevated versus nonbleeders ( P=0.96). In vitro experiments results: LVAD patient plasma caused abnormal angiogenesis with reduced tubule length ( P=0.04) and migration ( P=0.05). Similarly, endothelial cells grown with VWF degradation fragments exhibited reduced tubule length ( P<0.001) and migration ( P=0.01). Conclusions LVAD patients who bled from angiodysplasia had higher levels of VWF fragments than nonbleeders and gastrointestinal bleeders without angiodysplasia. VWF fragments caused abnormal angiogenesis in vitro. These findings suggest that VWF fragments may be a mechanistic link between LVAD support, abnormal angiogenesis, angiodysplasia, and gastrointestinal bleeding.

Von Willebrand disease in the elderly: clinical perspectives

Von Willebrand disease (VWD) is an inherited bleeding disorder that affects up to 1% of the population. In most cases, VWD results from a mutation in the von Willebrand Factor (VWF) gene, which alters the amount and function of VWF, a key glycoprotein in both primary and secondary hemostasis. A comprehensive analysis of patients with VWD should include VWF activity, antigen levels, platelet function, and a careful bleeding history. Treatment options include antifibrinolytics, desmopressin, and VWF replacement therapy. VWF levels fluctuate due to age, stress, environmental exposures, and pharmacologic treatment. Treatment guidelines exist to treat and prevent bleeding for patients undergoing surgery and medical procedures, but often these must be reevaluated in the setting of age-related comorbidities including cardiovascular events, venous thrombosis, and malignancy. In addition, many age-related complications are associated with a secondary acquired von Willebrand syndrome (AVWS), including malignancies, hypothyroidism, cardiovascular diseases, and cardiac replacement devices. The current literature is limited by a lack of older patients in clinical trials. Larger studies are needed to determine if age-related comorbidities affect VWD patients at different frequencies than the general elderly population. There is also a significant need for registry-based studies to evaluate many age-related comorbidities in VWD patients.

von Willebrand factor regulation of blood vessel formation

Several important physiological processes, from permeability to inflammation to hemostasis, take place at the vessel wall and are regulated by endothelial cells (ECs). Thus, proteins that have been identified as regulators of one process are increasingly found to be involved in other vascular functions. Such is the case for von Willebrand factor (VWF), a large glycoprotein best known for its critical role in hemostasis. In vitro and in vivo studies have shown that lack of VWF causes enhanced vascularization, both constitutively and following ischemia. This evidence is supported by studies on blood outgrowth EC (BOEC) from patients with lack of VWF synthesis (type 3 von Willebrand disease [VWD]). The molecular pathways are likely to involve VWF binding partners, such as integrin αvβ3, and components of Weibel-Palade bodies, such as angiopoietin-2 and galectin-3, whose storage is regulated by VWF; these converge on the master regulator of angiogenesis and endothelial homeostasis, vascular endothelial growth factor signaling. Recent studies suggest that the roles of VWF may be tissue specific. The ability of VWF to regulate angiogenesis has clinical implications for a subset of VWD patients with severe, intractable gastrointestinal bleeding resulting from vascular malformations. In this article, we review the evidence showing that VWF is involved in blood vessel formation, discuss the role of VWF high-molecular-weight multimers in regulating angiogenesis, and review the value of studies on BOEC in developing a precision medicine approach to validate novel treatments for angiodysplasia in congenital VWD and acquired von Willebrand syndrome.

Correction of a dominant-negative von Willebrand factor multimerization defect by small interfering RNA-mediated allele-specific inhibition of mutant von Willebrand factor

Essentials Substitution therapy for von Willebrand (VW) disease leaves mutant VW factor (VWF) unhindered. Presence of mutant VWF may negatively affect phenotypes despite treatment. Inhibition of VWF by allele-specific siRNAs targeting single-nucleotide polymorphisms is effective. Allele-specific inhibition of VWF p.Cys2773Ser improves multimerization.

SUMMARY

Background Treatment of the bleeding disorder von Willebrand disease (VWD) focuses on increasing von Willebrand factor (VWF) levels by administration of desmopressin or VWF-containing concentrates. Both therapies leave the production of mutant VWF unhindered, which may have additional consequences, such as thrombocytopenia in patients with VWD type 2B, competition between mutant and normal VWF for platelet receptors, and the potential development of intestinal angiodysplasia. Most cases of VWD are caused by dominant-negative mutations in VWF, and we hypothesize that diminishing expression of mutant VWF positively affects VWD phenotypes. Objectives To investigate allele-specific inhibition of VWF by applying small interfering RNAs (siRNAs) targeting common single-nucleotide polymorphisms (SNPs) in VWF. This approach allows allele-specific knockdown irrespective of the mutations causing VWD. Methods Four SNPs with a high predicted heterozygosity within VWF were selected, and siRNAs were designed against both alleles of the four SNPs. siRNA efficiency, allele specificity and siRNA-mediated phenotypic improvements were determined in VWF-expressing HEK293 cells. Results Twelve siRNAs were able to efficiently inhibit single VWF alleles in HEK293 cells that stably produce VWF. Transient cotransfections of these siRNAs with two VWF alleles resulted in a clear preference for the targeted allele over the untargeted allele for 11 siRNAs. We also demonstrated siRNA-mediated phenotypic improvement of the VWF multimerization pattern of the VWD type 2A mutation VWF p.Cys2773Ser. Conclusions Allele-specific siRNAs are able to distinguish VWF alleles on the basis of one nucleotide variation, and are able to improve a severe multimerization defect caused by VWF p.Cys2773Ser. This holds promise for the therapeutic application of allele-specific siRNAs in dominant-negative VWD.

Acquired coagulopathy in patients with left ventricular assist devices

Chronic heart failure (HF) is a major emerging healthcare problem, associated with a high morbidity and mortality. Left ventricular assist devices (LVADs) have emerged as a successful treatment option for patients with end-stage HF. Despite its great benefit, the use of LVAD is associated with a high risk of complications. Bleeding, pump thrombosis and thromboembolic events are frequently observed complications, with bleeding complications occurring in over a third of the patients. Although the design of the third-generation LVAD has improved greatly, these hemostatic complications still occur. The introduction of an LVAD into the circulatory system results in an altered hematological balance as a consequence of blood-pump interactions, changes in hemodynamics, the rheology, and the concomitant need for anticoagulation while implanted with an LVAD. The majority, if not all, LVAD patients experience a form of platelet dysfunction and impaired von Willebrand factor activity, leading to acquired coagulopathy disorders. Different diagnostic tools and treatment strategies have been reported; however, they require validation in LVAD patients. The present review focuses on acquired coagulopathies, describing the incidence, impact and underlying mechanism of acquired coagulopathy disorders in patients supported by LVADs. In addition, we will discuss diagnostic and management strategies for these acquired coagulopathies.

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.

Contemporary issues in the management of von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. Bleeding scores in VWD, focused in particular on mucosal bleeding, can be very useful in the diagnosis and validation of different types of treatment. The results of an extended prospective study with a large amount of information on clinical phenotype and implications in treatment are reviewed in this article. Treatment of mucosal and joint bleeding in severe VWD remains difficult in some patients. Due to the lack of data on the use of prophylaxis in these patients it is difficult to establish optimal treatment regimens. An overview of the literature, with a focus on the ongoing PRO.WILL study, is provided here. Furthermore, understanding the changes in von Willebrand factor (VWF) levels during pregnancy is very important for establishing the optimal management strategy for pregnancy and delivery in women with VWD. A recently published prospective observational cohort study in women with and without VWD during the postpartum period provides important data that should allow the improvement of postpartum treatment protocols.

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.

Determinants of bleeding phenotype in adult patients with moderate or severe von Willebrand disease

We performed a nation-wide cross-sectional study to evaluate determinants of bleeding symptoms in a large unselected cohort of adults with von Willebrand disease (VWD). VWD patients were included (n=664), based on lowest historically measured VWF:Ag and VWF:Act levels ≤30 U/dl. Menorrhagia (85%), cutaneous bleeding (77%), bleeding from minor wounds (77%) and oral-cavity bleeding (62%) occurred most frequently. Higher age was associated with a higher bleeding score (BS), determined according to Tosetto, in females. A 10 year increase in age was associated with 0.8 point (95% confidence interval [CI] 0.4–1.1) higher BS. Females had higher BS than males (median 12 vs. 10, p=0.012). BS differed significantly between VWD type 1, 2 and 3: median 9 (-2–31), 13 (-1–33) and 19.5 (1–35), respectively (p<0.001). BS was strongly associated with VWF and FVIII levels: individuals with VWF:Ag levels ≤10 IU/dl, VWF:Act ≤10 IU/dl and FVIII:C ≤10 IU/dl had, respectively, 5.3 point (95%CI 3.2–7.3), 4.3 point (95%CI 2.9–5.8) and 9.6 point (95%CI 6.5–12.7) higher BS, than those with levels >30 IU/dl. In type 3 patients 1 IU/dl FVIII:C decrease was associated with 0.6 point (95% CI 0.1–1.1) BS increase (p=0.021). In conclusion, in VWD patients the bleeding phenotype is strongly associated with type of VWD and VWF and FVIII levels.

Gastrointestinal angiodysplasia and bleeding in von Willebrand disease

Von Willebrand disease (VWD), the most common genetic bleeding disorder, is characterised by a quantitative or qualitative defect of von Willebrand factor (VWF). Patients with VWD suffer from mucocutaneous bleeding, of severity usually proportional to the degree of VWF defect. In particular, gastrointestinal bleeding associated with angiodysplasia is often a severe symptom of difficult management. This review focuses on the pathophysiology, diagnosis and treatment of VWD-associated gastrointestinal angiodysplasia and related bleeding.

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.

Continuous-Flow LVAD Support Causes a Distinct Form of Intestinal Angiodysplasia

Rationale:

The objective of this autopsy study was to determine whether gastrointestinal angiodysplasia develops during continuous-flow left ventricular assist device (LVAD) support.

Objective:

LVAD support causes pathologic degradation of von Willebrand factor (vWF) and bleeding from gastrointestinal angiodysplasia at an alarming rate. It has been speculated that LVAD support itself may cause angiodysplasia. The relationship to abnormal vWF metabolism is unknown. We tested the hypothesis that abnormal gastrointestinal vascularity develops during continuous-flow LVAD support.

Methods and Results:

Small bowel was obtained from deceased humans, cows, and sheep supported with a continuous-flow LVAD (n=9 LVAD, n=11 control). Transmural sections of jejunum were stained with fluorescein isothiocyanate–conjugated isolectin-B4 for endothelium to demarcate vascular structures and quantify intestinal vascularity. Paired plasma samples were obtained from humans before LVAD implantation and during LVAD support (n=41). vWF multimers and degradation fragments were quantified with agarose and polyacrylamide gel electrophoresis and immunoblotting. Abnormal vascular architecture was observed in the submucosa of the jejunum of human patients, cows, and sheep supported with a continuous-flow LVAD. Intestinal vascularity was significantly higher after LVAD support versus controls (5.2±1.0% versus 2.1±0.4%, P =0.004). LVAD support caused significant degradation of high–molecular-weight vWF multimers (–9±1%, P <0.0001) and accumulation of low–molecular-weight vWF multimers (+40±5%, P <0.0001) and vWF degradation fragments (+53±6%, P <0.0001).

Conclusions:

Abnormal intestinal vascular architecture and LVAD-associated vWF degradation were consistent findings in multiple species supported with a continuous-flow LVAD. These are the first direct evidence that LVAD support causes gastrointestinal angiodysplasia. Pathologic vWF metabolism may be a mechanistic link between LVAD support, abnormal angiogenesis, gastrointestinal angiodysplasia, and bleeding.

Current and Emerging Options for the Management of Inherited von Willebrand Disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder with an estimated prevalence of ~1% and clinically relevant bleeding symptoms in approximately 1:10,000 individuals. VWD is caused by a deficiency and/or defect of von Willebrand factor (VWF). The most common symptoms are mucocutaneous bleeding, hematomas, and bleeding after trauma or surgery. For decades, treatment to prevent or treat bleeding has consisted of desmopressin in milder cases and of replacement therapy with plasma-derived concentrates containing VWF and Factor VIII (FVIII) in more severe cases. Both are usually combined with supportive therapy, e.g. antifibrinolytic agents, and maximal hemostatic measures. Several developments such as the first recombinant VWF concentrate, which has been recently licensed for VWD, will make a more "personalized" approach to VWD management possible. As research on new treatment strategies for established therapies, such as population pharmacokinetic-guided dosing of clotting factor concentrates, and novel treatment modalities such as aptamers and gene therapy are ongoing, it is likely that the horizon to tailor therapy to the individual patients' needs will be extended, thus, further improving the already high standard of care in VWD in most high-resource countries.