How I treat patients with von Willebrand disease

A Systematic Review of Efficacy and Safety of Plasma-Derived von Willebrand Factor/Factor VIII Concentrate (Voncento) in von Willebrand Disease

BACKGROUND

 For the treatment of von Willebrand disease (VWD), von Willebrand factor (VWF) concentrates can be used in on-demand, long-term prophylaxis, and surgical prophylaxis regimens.

METHODS

 This systematic literature review was conducted to evaluate the efficacy, consumption, and safety of plasma-derived human coagulation FVIII/human VWF (pdVWF/FVIII; Voncento/Biostate) for the treatment of patients with any inherited VWD type. An electronic search was conducted in MEDLINE and Cochrane Library databases on VWD therapies. All retrieved publications were assessed against predefined inclusion/exclusion criteria following the Cochrane group recommendations. Associated pharmacovigilance data were collected across the same time period.

RESULTS

 Eleven publications from eight study cohorts were identified for data retrieval. All were from multicenter studies and included both pediatric and adult patients. Eight publications included evaluations of the efficacy of pdVWF/FVIII for on-demand treatment, eight included long-term prophylactic treatment, and eight included surgical prophylaxis. Treatment protocols and VWF administration methods differed between studies, as did safety evaluations. The clinical response was rated as excellent/good for on-demand treatment in 66 to 100% of nonsurgical bleeds, 89 to 100% in the treatment of breakthrough bleeds during long-term prophylaxis treatment, and hemostatic efficacy in surgical procedures was 75 to 100%. Pharmacovigilance data confirmed a low incidence of adverse events in treated patients.

CONCLUSION

 This review provides a comprehensive summary of studies that evaluated the use of pdVWF/FVIII in VWD demonstrating the long-term effectiveness and safety of this pdVWF/FVIII across all ages, types of VWD, and treatment settings.

Targeting von Willebrand disease: the current status and future directions of management therapies

INTRODUCTION

von Willebrand disease (VWD) is the commonest inherited bleeding disorder, and is typically caused by deficits in the quantity or quality of von Willebrand factor (VWF).

AREAS COVERED

This review describes the main clinical, diagnostic, and therapeutic aspects of VWD, with particular attention to its management. In addition, standard and avant-garde replacement therapies based on the use of VWF are discussed.

EXPERT OPINION

The goal of treatment for VWD is to reverse the double hemostatic defect resulting from the abnormal or reduced expression of VWF and the concomitant factor VIII (FVIII) deficiency. Treatment consists of managing any bleeds and both short-term prophylaxis (i.e. for surgery or invasive procedures) and long-term prophylaxis. While desmopressin is suitable for most patients with type 1 VWD, VWF/FVIII concentrates are the treatment of choice for the other types of VWD. Beside plasma-derived VWF/FVIII concentrates, whose safety and efficacy have been demonstrated by several clinical trials, products containing only VWF, obtained by plasma fractionation and recombinant DNA technology, have become available and marketed more recently. The clinical use of these VWF-only products is particularly attractive in the setting of surgery and long-term prophylaxis, such as the prevention of recurrent gastrointestinal bleeding in cases of angiodysplasia.

The diagnosis, natural history, and management of von Willebrand disease in women in the age of guidelines

INTRODUCTION

Women and girls with bleeding disorders face multiple bleeding challenges throughout their life. The most significant morbidity and mortality are due to heavy menstrual bleeding and postpartum hemorrhage in their reproductive years. The ASH/ISTH/NHF/WFH 2021 guidelines on diagnosing and managing von Willebrand disease (VWD) provide several new updates.

AREAS COVERED

Women with VWD have a higher prevalence of heavy menstrual bleeding. The subpopulation of adolescents is particularly vulnerable, as the diagnosis is often delayed with increased comorbidity of iron deficiency anemia and associated symptoms. A detailed review is done on the prevalence of bleeding-related complications, especially heavy menstrual bleeding (HMB) and post-partum hemorrhage (PPH). The management strategies are also reviewed in detail, with a specific focus on the target factor levels and the use of antifibrinolytics.

EXPERT OPINION

The 2021 ASH/ISTH/NHF/WFH diagnostic and management recommendations are reviewed with a specific focus on hormonal methods of HMB management and antifibrinolytics in this situation. The reviewed topics include neuraxial anesthesia, factor cutoff, and tranexamic acid use in the postpartum period.

Longitudinal bleeding assessment in von Willebrand disease utilizing an interim bleeding score

BACKGROUND

Assessment of bleeding phenotype is critically important in the diagnosis of von Willebrand disease (VWD). Despite advances in bleeding assessment tools (BATs), standardized tools to evaluate bleeding following diagnosis (interim bleeding) are lacking.

OBJECTIVES

We assessed the clinical utility of an interim bleeding protocol in a multicenter, international study involving patients with VWD.

METHODS

The enrolment ISTH BAT formed the original bleeding score (0 BS). At follow-up, the International Society on Thrombosis and Haemostasis BAT was repeated but included only interval bleeding (Interim BS, 1 BS). Both scores were annualized (0 BS/yr, 1 BS/yr). BS were analyzed by VWD subtype, plasma VWF level, sex, and age.

RESULTS

Interim BS discriminated by subtype, with significantly increased 0 BS and 1 BS in patients with type 3 VWD. In patients with type 1 VWD, a positive or negative 0 BS did not predict future bleeding, with similar 1 BS/yr (median 1.0 vs. 0.7, p = .2). Despite significantly higher 0 BS in females with type 1 VWD than males (median 7 vs. 5, p = .0012), 1 BS were not significantly different (median 4 vs. 4, p = .16). While 0 BS were lower in children than adults with type 1 VWD, interim BS were similar (median 5 vs. 3, p = .5; 1BS/yr, median 1 vs. 0.8, p = .7). Interestingly, in those with plasma von Willebrand factor:ristocetin cofactor levels >50 IU/dl, interim BS rates were similar to those 30-50 IU/dl (1 BS/yr 0.8 vs. 1.3, p = .5).

CONCLUSION

This study provides both a new approach to longitudinal bleeding assessment and insights into the evolution of bleeding in VWD.

Prophylactic management of patients with von Willebrand disease

Von Willebrand disease, the most common inherited bleeding disorder that affects both males and females, is due to quantitative or qualitative defects of the multimeric glycoprotein von Willebrand factor, which cause mucous membrane bleeding but also soft tissue bleeding owing to the secondary deficiency of factor VIII. The aim of treatment is to correct this dual defect of hemostasis. In addition to the episodic management of bleeding episodes, therapy includes their short- or long-term prevention. Short-term prophylaxis is mainly warranted in order to provide effective hemostatic coverage to patients undergoing surgery or invasive procedures and to affected women at the time of delivery or during menstruations associated with excessive bleeding. The aim of long-term prophylaxis is to prevent bleeding in particular categories of patients at increased risk of frequent and spontaneous bleeding in the joints, nose, and gastrointestinal tract.

von Willebrand disease: what does the future hold?

von Willebrand disease (VWD) is characterized by its heterogeneous clinical manifestation, which complicates its diagnosis and management. The clinical management of VWD has remained essentially unchanged over the last 30 years or so, using von Willebrand factor (VWF) concentrates, desmopressin, and anti-fibrinolytic agents as main tools to control bleeding. This is in contrast to hemophilia A, for which a continuous innovative path has led to novel treatment modalities. Despite current VWD management being considered effective, quality-of-life studies consistently reveal a higher than anticipated burden of VWD on patients, which is particularly true for women. Apparently, despite our perceived notion of current therapeutic efficiency, there is space for innovation with the goal of reaching superior efficacy. Developing innovative treatments for VWD is complex, especially given the heterogeneity of the disease and the multifunctional nature of VWF. In this perspective article, we describe several potential strategies that could provide the basis for future VWD treatments. These include genetic approaches, such as gene therapy using dual-vector adenoassociated virus and transcriptional silencing of mutant alleles. Furthermore, protein-based approaches to increase factor FVIII levels in VWD-type 3 or 2N patients are discussed. Finally, antibody-based options to interfere with VWF degradation (for congenital VWD-type 2A or acquired von Willebrand syndrome-type 2A) or increase endogenous VWF levels (for VWD-type 1) are presented. By highlighting these potential strategies, we hope to initiate an innovative path, which ultimately would allow us to better serve VWD patients and their specific needs.

Von Willebrand disease type 2N: An update

Quantitative or qualitative defects of von Willebrand factor (VWF) are responsible for the most common inherited bleeding disorder, von Willebrand disease (VWD). Type 2N VWD is an uncommon recessive disorder that results from gene mutations located in the region coding for the binding site of VWF for factor VIII (FVIII). This narrative review describes the pathophysiology, diagnostic procedures and treatment as well as the molecular biology of type 2N VWD. Although other VWF-dependent functions like binding to platelets and collagen are preserved, FVIII plasma levels are low due to the rapid clearance of this moiety in the absence or reduction of its binding to VWF. The diagnosis of type 2N should be considered in patients with low FVIII coagulant activity (FVIII:C) and disproportionally higher VWF antigen, especially when they present with an autosomal recessive pattern of inheritance. Because an accurate diagnosis is essential for genetic counseling and optimal treatment, type 2N must be distinguished from mild/moderate hemophilia A and its carrier state. This differential diagnosis can be obtained by using the laboratory assay of the FVIII binding capacity of VWF (VWF:FVIIIB) or analysis of the FVIII binding site on the VWF gene.

An Open-Label Extension Study to Assess the Long-Term Efficacy and Safety of a Plasma-Derived von Willebrand Factor (VWF)/Factor VIII (FVIII) Concentrate in Patients with von Willebrand Disease (SWIFT-VWDext Study)

Objective

Plasma-derived von Willebrand factor/factor VIII (pdVWF/FVIII; VONCENTO^®, CSL Behring) is a high-concentration, low-volume, high-purity concentrate, which contains a high level of high-molecular-weight multimers and a VWF/FVIII ratio of ~2.4:1. The SWIFT ("Studies with von Willebrand factor/Factor VIII") program is evaluating pdVWF/FVIII in patients with von Willebrand disease (VWD). The long-term efficacy and safety profile of pdVWF/FVIII was investigated in this multicenter, open-label, extension study.

Methods

Pediatric, adolescent, and adult patients with VWD who required treatment of non-surgical bleeds (NSBs), treatment during surgical events or who were receiving prophylaxis and who had completed one of two previous clinical trials of pdVWF/FVIII were included. Efficacy and safety analyses were performed for on-demand (n=10), prophylaxis (n=8), or on-demand and prophylaxis (n=2) treatment in patients pre-treated with pdVWF/FVIII for ≥12 months.

Results

Seven patients experienced a total of 402 NSBs in the on-demand arm, of which 77 required treatment and nine NSB events in three patients were considered major. Nine patients reported 118 NSBs in the prophylaxis arm, with 96 events requiring treatment and seven patients experiencing 12 major NSB events. Excellent or good hemostatic efficacy was reported by the investigator for 98.7% (on-demand) and 97.9% (prophylaxis) of NSB events treated with pdVWF/FVIII, without relevant differences between subgroups by age. pdVWF/FVIII was well tolerated, and the adverse events seen were mild-moderate and consistent with the safety profile for this product seen in other studies. There were no cases of anaphylactic reactions and angioedema, development of VWF/FVIII inhibitors, thromboembolic events, or viral infections.

Conclusion

This contemporary comprehensive development program evaluating pdVWF/FVIII across all ages demonstrates long-term safety and efficacy for treatment and prevention of bleeds in patients with severe VWD, supporting the benefit-risk profile of pdVWF/FVIII.

Pharmacokinetics, Efficacy and Safety of a Plasma-Derived VWF/FVIII Concentrate (Formulation V) in Pediatric Patients with von Willebrand Disease (SWIFTLY-VWD Study)

Purpose

Formulation V (VONCENTO^®) is a plasma-derived high-concentration/low-volume, high-purity von Willebrand factor (VWF)/factor VIII (FVIII) concentrate, originally indicated for von Willebrand disease (VWD) in adults and adolescents. This multicenter, open-label study (SWIFTLY-VWD) evaluated the pharmacokinetics (PK), as well as hemostatic efficacy and safety, of Formulation V in pediatric patients (<12 years) with severe VWD requiring treatment or prophylaxis of bleedings.

Methods

PK investigations were performed following one dose of Formulation V at Day 1 and 180. Nonsurgical bleeds were analyzed, while hemostatic efficacy was graded as excellent/good/moderate/none. Safety assessments included adverse events, and presence of VWF and/or FVIII inhibitors.

Results

Formulation V was administered as on-demand (N=13) or prophylaxis therapy (N=4) for 12 months (<6 years, N=9; 6 to <12 years, N=8). PK parameters for VWF markers were generally comparable to adults but showed lower VWF:ristocetin cofactor (RCo) exposure. Incidence of major bleeds was lower for prophylaxis (3.3%) than on-demand therapy (27.1%); joint bleeds were also lower (3.3% vs 11.5%, respectively). Investigator-reported excellent/good hemostatic efficacy against nonsurgical bleeds was 100%. No clinically relevant differences in PK, hemostatic efficacy, or safety were observed between age-groups (<6 years and 6 to <12 years). Formulation V was well tolerated. Adverse events were mild–moderate and consistent with the adult safety profile. No cases of anaphylactic reactions or angioedema, development of FVIII/VWF inhibitors, thromboembolic events, or viral infections were reported.

Conclusion

This study provides evidence for use of Formulation V to treat and prevent bleeding in pediatric patients with severe VWD, and led to the European approval of Formulation V in children.

Women and inherited bleeding disorders - A review with a focus on key challenges for 2019

The area of women and inherited bleeding disorders has undergone quick expansion in recent years. More patients are being identified and expertise to diagnose and manage these patients is now essential for practising physicians. Programs to help educate and empower patients and caregivers are now in place. Common inherited bleeding disorders affecting women include von Willebrand disease (VWD), inherited platelet disorders, and rare inherited bleeding disorders such as factor VII (FVII) deficiency and factor XI (FXI) deficiency. Specific clinical tools have been developed to help clinicians and patients screen for the presence of these bleeding disorders in both adult and pediatric populations. Affected women can experience heavy menstrual bleeding and resulting iron deficiency anemia, postpartum hemorrhage, and hemorrhagic ovarian cysts which need to be properly managed. Excessive bleeding can adversely affect quality of life in these women. Front line therapy for bleeding in mild cases focuses on the use of non-specific hemostatic agents such as DDAVP ®, tranexamic acid and hormonal agents but specific factor replacement and/or blood products may be required in more severe cases, in severe bleeding or as second line treatment when bleeding is not responsive to first line agents. Iron status should be optimised in these women especially in pregnancy and use of an electronic app can now help clinicians achieve this. These patients should ideally be managed by a multidisciplinary team whenever possible even remotely. Although clinical research has closed some knowledge gaps regarding the diagnosis and management of these women, there remains significant variation in practise and lack of evidence-based guidelines still exists in many spheres of clinical care in which caregivers must rely on expert opinion. Ongoing efforts in education and research will continue to improve care for these women and restore quality of life for them.

Significant gynecological bleeding in women with low von Willebrand factor levels

Gynecological bleeding is frequently reported in women with von Willebrand disease (VWD). Low von Willebrand factor (VWF) may be associated with significant bleeding phenotype despite only mild plasma VWF reductions. The contribution of gynecological bleeding to this phenotype has yet to be described. The optimal clinical bleeding assessment tool (BAT) to evaluate bleeding remains unclear. Using a standardized approach to phenotypic assessment, we evaluated gynecological bleeding and directly compared the Condensed Molecular and Clinical Markers for the Diagnosis and Management of type 1 VWD (Condensed MCMDM-1 VWD) and International Society on Thrombosis and Haemostasis (ISTH) BAT scores in 120 women enrolled in the Low von Willebrand in Ireland Cohort study. Heavy menstrual bleeding (HMB) was reported in 89% of female participants; 45.8% developed iron deficiency. Using identical data, Condensed MCMDM-1 VWD menorrhagia domain scores were significantly lower than ISTH BAT scores (2 vs 3; P < .0001), the discrepant results related to 40% of women not seeking medical consultation for HMB, reducing the sensitivity of the Condensed score. For those who reported HMB to physicians, the low VWF diagnosis was not expedited (age at diagnosis 34.2 vs 33.4 years in women failing to present; P = .7). Postpartum hemorrhage (PPH) was self-reported in 63.5% of parous women (n = 74); 21.6% required transfusion, critical care, radiological, or surgical intervention. Our data demonstrate that gynecological bleeding is frequently reported in women with low VWF; despite pregnancy-related increases in plasma VWF levels, these women may experience PPH. Defining the optimal management approach for these patients requires further research. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

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.

Efficacy of Octocog Alfa (Advate) in a Child with Type 3 von Willebrand Disease and Alloantibodies

Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder and is caused by either a quantitative and/or qualitative defect of the multimeric glycoprotein vonWillebrand factor (VWF).[...].

Pharmacokinetics, efficacy, and safety of a plasma-derived VWF/FVIII concentrate (VONCENTO) for on-demand and prophylactic treatment in patients with von Willebrand disease (SWIFT-VWD study)

Supplemental Digital Content is available in the text

VONCENTO (CSL Behring Gmbh, Marburg, Germany) is a plasma-derived, high concentration, lower volume [relative to HAEMATE P (CSL Behring)], high-purity von Willebrand factor (VWF)/factor VIII (FVIII) concentrate with a VWF/FVIII ratio similar to HAEMATE P. This open-label, multicentre study investigated the pharmacokinetic, haemostatic efficacy, and safety profiles of VONCENTO in study participants at least 12 years of age with von Willebrand disease (VWD) who required treatment of nonsurgical bleeding (NSB) events or underwent surgery or prophylaxis. The first 12-month on-demand treatment period comprised a pharmacokinetic investigation and an efficacy analysis. After 12 months, qualifying study participants were switched to prophylactic therapy and included in a further 12-month efficacy analysis. In total, 21 study participants (including three adolescents, and 13 study participants with VWD type 3) received VONCENTO as on-demand treatment for 12 months. ‘Excellent’/‘good’ haemostatic efficacy was achieved in 98.3% of the 407 NSB events assessed by investigators. Following the switch to prophylactic treatment, the total number of NSBs in eight patients markedly decreased from 304 to 10 (with haemostatic efficacy judged to be ‘excellent’ for all). The annualised bleeding rate also significantly decreased from a median of 26.5 events to one event. Safety assessments showed no inhibitory antibodies to either FVIII or VWF, no transmission of infectious agents, no thromboembolic events and no treatment-related serious adverse events. VONCENTO was shown to be well tolerated and provided excellent haemostatic efficacy in the treatment of bleeds or during prophylaxis in study participants with VWD, including also those with type 3, the severest form of VWD.

Laboratory monitoring of replacement therapy for major surgery in von Willebrand disease

Von Willebrand disease (VWD) is an inherited haemorrhagic disorder caused by a quantitative or qualitative defect of von Willebrand factor (VWF), a multimeric plasma glycoprotein that plays a key role in platelet adhesion to the subendothelium and acts as a carrier of factor VIII (FVIII) in blood. Patients with VWD experience bleeding symptoms that are mainly localized in mucous membranes and soft tissues, and their severity depends on the degree of the primary reduction in VWF and the secondary deficiency of FVIII in plasma. Because VWD patients are also at increased risk of perioperative bleeding, a prophylactic treatment aimed to correct the dual haemostatic defect (i.e. VWF and FVIII) is warranted. This review summarizes knowledge on the current management of patients undergoing major surgery, focusing on the peri-surgical laboratory monitoring of replacement therapy with VWF/FVIII concentrates. We suggest to monitor plasma levels of FVIII coagulant activity in the postoperative period rather than a surrogate maker of platelet-binding VWF activity as the ristocetin cofactor assay and its recent modifications.

Congenital and acquired bleeding disorders in pregnancy

Obstetrical hematology represents challenges not only for the patient, but also for her progeny. In particular, bleeding disorders, both congenital and acquired, not only present problems both for delivery and in the immediate postpartum period, but also may have significant implications for the fetus and neonate. Women with congenital bleeding disorders or who are carriers of X-linked or autosomal disorders should be counseled prior to conception so that pregnancy can be safely undertaken with careful preparation. A treatment plan should be set up by a specialized care team that includes the hematologist, obstetrician, and anesthesiologist; the patient should be followed closely during pregnancy, through delivery, and in the immediate postpartum period. Acquired disorders of hemostasis that occur with pregnancy may present particular diagnostic difficulties and require rapid diagnosis and management.

The Von Willebrand Factor A1-Collagen III Interaction Is Independent of Conformation and Type 2 Von Willebrand Disease Phenotype

The blood von Willebrand factor (VWF) mediates platelet adhesion to injured vessels by sequestering platelets from blood flow and depositing them to collagen and other exposed subendothelial matrix proteins. This process of capturing platelets to facilitate formation of platelet plugs occurs through transient interactions with platelet glycoprotein Ibα via the VWF A1 domain which also binds collagen. Using a conformationally diverse collection of natively folded and mutation-induced misfolded von Willebrand disease (VWD) variants, we test a recently proposed affinity up-regulation hypothesis which states that collagen binding changes the conformation of the A1 domain to a high-affinity GPIbα binding competent state. With surface plasmon resonance (SPR), we present this diversified collection to collagen and quantify the kinetics of association and dissociation to ascertain the conformational selectivity of collagen. With analytical rheology, we quantify real-time platelet pause times and translocation velocities across a Cu²⁺ HisTag-chelated and collagen-bound A1 single domain and A1A2A3 tridomain fragment of VWF under shear stress in an ex vivo shear flow microfluidic chamber. In contrast to expected hypothetical outcomes, collagen has limited conformational selectivity for binding A1. A1-collagen binding is independent of gain- or loss-of-function phenotype and under shear stress, platelet translocation pause times on collagen-bound A1A2A3 are either normal or shorter depending on whether A1 is concertedly bound with the A3 domain to collagen. With respect to A1, collagen has an inhibitory role that provides an explanation for the lack of thrombosis in patients with gain-of-function VWD.

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.

Effect of the Novel Biodegradable N, O-Carboxymethylchitosan and Oligo-Chitosan on the Platelet Thrombogenicity Cascade in von Willebrand Disease

INTRODUCTION

Von Willebrand disease (vWD) is the second least common hemostatic disorder in Malaysia, and it has a low prevalence. This study examined the underlying platelet thrombogenicity cascades in the presence of different formulations of chitosan-derivatives in vWD patients. This paper aimed to determine the significant influence of chitosan biomaterial in stimulating the platelet thrombogenicity cascades that involve the von Willebrand factor, Factor 8, Thromboxane A2, P2Y12 and Glycoprotein IIb/IIIa in vWD.

MATERIALS AND METHODS

Variable chitosan formulations of N,O-Carboxymethylchitosan (NO-CMC) and Oligo-Chitosan (O-C) were tested. Fourteen vWD subjects voluntarily participated in this study after signing informed consent forms. The patient's demographic profiles, family history, type of vWD, clinical symptoms and laboratory profiles were recorded and analyzed. Enzyme-linked immunosorbent assay, flow cytometry and Western blot tests were used to determine the level of the chitosan-adhered-platelet-mechanisms.

RESULTS

The study revealed that most patients were predominantly affected by vWD type I. The O-C group of chitosan's scaffold pores is sufficient to allow for nutrients and cells. The O-C-stimulated-mediators are capable of initiating the platelet actions and were detected to expedite the blood coagulation processes. The oligo-group of chitosans was capable of amplifying and triggering more platelet activator's pathways via the studied mediators. The present findings suggest that the ability of each type of chitosan to coagulate blood varies depending on its chemical composition.

CONCLUSION

The oligo group of chitosans is potentially capable of triggering platelet thrombogenicity cascades by activating platelets in vWD patients to form a platelet plug for hemostasis process.

von Willebrand disease and platelet disorders

The diagnosis and management of bleeding disorders is made difficult by the complexity and variety of disorders, clinical symptoms and bleeding type and severity. von Willebrand disease (VWD) and platelet disorders are disorders of primary haemostasis and together represent the most common inherited bleeding disorders. In this article, we describe the diagnosis of VWD and platelet disorders and the treatment options for VWD.

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.

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.

Advances in the diagnosis and management of von Willebrand disease

von Willebrand disease (VWD), the most common inherited bleeding disorder, is caused by a quantitative (type 1 and 3) or qualitative (type 2) defect of von Willebrand factor (VWF). In this review, the present knowledge regarding the diagnosis and the management of VWD is briefly analyzed.

Onset of severe refractory thrombocytopenia following surgery in a patient with type 2B von Willebrand disease—A case report

A case of a severe thrombocytopenia occurring in a patient with type 2B von Willebrand disease following an esophagectomy is described. As platelet transfusions were ineffective due to alloimunization, effective hemostasis was achieved only with the factor VIII/von Willebrand factor concentrate Haemate P.

Accelerated uptake of VWF/platelet complexes in macrophages contributes to VWD type 2B-associated thrombocytopenia

Von Willebrand disease (VWD) type 2B is characterized by mutations causing enhanced binding of von Willebrand factor (VWF) to platelets. Bleeding tendency is associated with heterogeneous clinical manifestations, including moderate to severe thrombocytopenia. The underlying mechanism of the thrombocytopenia has remained unclear. Here, a mouse model of VWD type 2B was used to investigate pathways contributing to thrombocytopenia. Immunohistochemical analysis of blood smears revealed that mutant VWF was exclusively detected on platelets of thrombocytopenic VWD type 2B mice, suggesting that thrombocytopenic VWD type 2B mice were elevated two- to threefold upon chemical macrophage depletion. Colocalization of platelets with CD68-positive Kupffer cells and CD168-positive marginal macrophages in liver and spleen, respectively, confirmed the involvement of macrophages in the removal of VWF/platelet complexes. Significantly more platelets were found in liver and spleen of VWD type 2B mice compared with control mice. Finally, platelet survival was significantly shorter in VWD type 2B mice compared with control mice, providing a rationale for lower platelet counts in VWD type 2B mice. In conclusion, our data indicate that VWF type 2B binds to platelets and that this is a signal for clearance by macrophages, which could contribute to the thrombocytopenia in patients with VWD type 2B.

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 use of DDAVP in children with bleeding disorders

Desmopressin (1-deamino-8-D-arginine vasopressin, DDAVP) has been used in children with von Willebrand disease (VWD) and Hemophilia A for almost 35 years. This treatment has substantially lowered the number of children exposed to human plasma derived products, with a good safety profile, and at very low cost. The response to DDAVP has been shown to be associated with age, baseline factor level, and genetic mutations. A DDAVP challenge test is recommended. DDAVP has also been used to prevent and treat bleeding episodes in children with platelet function defects and other disorders associated with bleeding tendency.

Women and bleeding disorders

SUMMARY

While women are rarely affected by haemophilia, they are equally as likely as men to have other bleeding disorders. Menorrhagia, or heavy menstrual bleeding, is the most common symptom that they experience. Not only is menorrhagia more prevalent among women with bleeding disorders, but bleeding disorders are more prevalent among women with menorrhagia. Although menorrhagia is the most common reproductive tract manifestation of a bleeding disorder, it is not the only manifestation. Women with bleeding disorders appear to be at an increased risk of developing haemorrhagic ovarian cysts and possibly endometriosis. Women suspected of having a bleeding disorder or being a carrier of haemophilia should be offered diagnostic testing before getting pregnant to allow for appropriate preconception counselling and pregnancy management. During pregnancy, women with bleeding disorders may be at an increased risk of bleeding complications. At the time of childbirth, women with bleeding disorders appear to be more likely to experience postpartum haemorrhage, particularly delayed or secondary postpartum haemorrhage. As women with bleeding disorders grow older, they may be more likely to manifest gynaecological conditions which present with bleeding. Women with bleeding disorders are more likely to undergo a hysterectomy and are more likely to have the operation at a younger age. While women with bleeding disorders are at risk for the same obstetrical and gynaecological problems that affect all women, women with bleeding disorders are disproportionately affected by conditions that manifest with bleeding. Optimal management involves the combined expertise of haemostasis experts and obstetrician-gynaecologists.

Obstetric management of adolescents with bleeding disorders

Adolescents with bleeding disorders who become pregnant must contend with the dual challenges of their bleeding disorder and their pregnancy. Adolescents are more likely to terminate a pregnancy than adult women, and when they do carry a pregnancy, they are more likely to deliver prematurely. Otherwise, they are at risk for the same complications that adult women with bleeding disorders experience, particularly bleeding complications postpartum. Since one half to two thirds of adolescent pregnancies are unplanned, issues related to reproduction should be addressed during routine visits with the pediatrician, hematologist or gynecologist. Girls who are at risk of being carriers for hemophilia A and B, severe von Willebrand disease, and other severe bleeding disorders should have their bleeding disorder status determined before they become pregnant. During pregnancy, a plan should be established to ensure that both mother and fetus deliver safely. Young women at risk for severe bleeding or at risk of having a severely affected infant should be referred for prenatal care and delivery to a center where, in addition to specialists in high-risk obstetrics, there is a hemophilia treatment center or a hematologist with expertise in hemostasis. Prior to delivery or any invasive procedures, young women at risk for severe bleeding should receive prophylaxis. Since administration of desmopressin may result in hyponatremia, whenever available, virally inactivated or recombinant clotting factor concentrates should be used for replacement as opposed to fresh frozen plasma or cryoprecipitate.

Von Willebrand disease in foot and ankle surgery

Level of Evidence: V, Expert Opinion

How I treat von Willebrand disease

Recent multicenter studies have clarified the molecular basis underlying the different von Willebrand disease (VWD) types, all of which are caused by the deficiency and/or abnormality of von Willebrand factor (VWF). These studies have suggested a unifying pathophysiologic concept. The diagnosis of VWD, remains difficult because its clinical and laboratory phenotype is very heterogeneous and may overlap with normal subjects. Stringent criteria are therefore required for a clinically useful diagnosis. In this paper, we delineate a practical approach to the diagnosis and treatment of VWD. Our approach is based on the critical importance of a standardized bleeding history that has been condensed into a final bleeding score and a few widely available laboratory tests, such as VWF ristocetin cofactor activity, VWF antigen and factor VIII. This approach would help identify those subjects who will probably benefit from a diagnosis of VWD. The next step involves performing a trial infusion with desmopressin in all patients who fail to exhibit an enhanced responsiveness to ristocetin. On the basis of these results and through a series of illustrative examples, the clinician will be able to select the best approach for the optimal management of VWD, according to the patient's characteristics and clinical circumstances.

Treatment and prevention of acute bleedings in von Willebrand disease--efficacy and safety of Wilate, a new generation von Willebrand factor/factor VIII concentrate

For many patients with von Willebrand disease (VWD), the replacement therapy with von Willebrand factor (VWF)/factor VIII (FVIII) concentrates is the treatment of choice. To evaluate clinical efficacy, safety and tolerability of Wilate, an albumin-free VWF/FVIII concentrate with a ratio of the two haemostatic moieties of approximately 1 to 1, a prospective clinical programme has been designed. The dataset on the treatment and prevention of bleedings is derived from 44 patients (20 males and 24 females) of all VWD types. Thousand and ninety five bleeding episodes were treated with an overall efficacy rating of excellent or good in 96%. The median dose per treatment day was 26 IU FVIII:C per kg. Eighty-one per cent of bleeds were stopped within 1 or 2 days. Gastrointestinal (GI) bleeds needed higher doses (mean 44 IU kg(-1)) and longer treatment (mean 4 days). Efficacy and dosing data from eight children of 12 or less years of age did not differ significantly from the overall study population. Nineteen patients, including six children, were treated prophylactically for more than 3 months (mean 14.8, range 3-46) with a mean prophylactic dose of 27.4 IU kg(-1) and a mean frequency of 1.9 infusions per week. A drop of bleeding frequency from a mean of 4.5 to 1.4 bleeds per month was observed. The overall tolerability was very good. Adverse drug reactions were rare and were mild or moderate in their intensity. The large prospective clinical dataset shows that Wilate is efficacious and safe in the treatment and prevention of haemorrhages in all VWD types in both adult and paediatric patients.

Evidence-based recommendations on the treatment of von Willebrand disease in Italy

BACKGROUND

von Willebrand disease (VWD) is the most common hereditary bleeding disorder affecting both males and females. It arises from quantitative or qualitative defects of von Willebrand factor (VWF) and causes bleeding of mucous membranes and soft tissues. The aim of treatment is to correct the dual defect of haemostasis caused by the abnormal/reduced VWF and the concomitant deficiency of factor VIII (FVIII).

MATERIAL AND METHODS

This document contains evidence-based recommendations for the management of VWD compiled by AICE (the Italian Association of Haemophilia Centres). All the evidence supporting these recommendations are based on non-randomised comparative studies or case series, because randomised controlled clinical trials or meta-analyses are not available for this disease.

RESULTS AND CONCLUSIONS

Desmopressin (DDAVP) is the treatment of choice for patients with type 1 VWD with FVIII and VWF levels of 10 U/dL or more, while VWF/FVIII concentrates are indicated for those who are unresponsive or insufficiently responsive to DDAVP (severe type 1, type 2 and 3 VWD). VWF concentrates devoid of FVIII, not yet licensed in Italy, may be considered for short-term prophylaxis in elective surgery or for long-term secondary prophylaxis.

The Role Of von Willebrand Factor In Hemorrhagic And Thrombotic Disorders

von Willebrand factor (VWF) is a multimeric plasma protein that mediates platelet adhesion as well as platelet aggregation at sites of vascular injury and acts as a carrier of factor VIII. Although acquired or inherited VWF deficiency is associated with a bleeding tendency, there is increasing evidence that VWF has a pivotal role in thrombogenesis. In fact, while the presence in the plasma of unusually large VWF multimers, due to a congenital or acquired deficiency of a VWF-cleaving metalloprotease, has been implicated in the pathogenesis of thrombotic thrombocytopenic purpura, high plasma levels of VWF have been associated with an increased risk of both arterial and venous thrombosis. The role of VWF in normal and pathological hemostasis is discussed in this review, and important advances in the pathophysiology, diagnosis, and treatment of VWF-associated disorders are also described.

Clinical efficacy in bleeding and surgery in von Willebrand patients treated with Fanhdi a highly purified, doubly inactivated FVIII/VWF concentrate

Therapy with factor VIII/von Willebrand factor (FVIII/VWF) concentrate is the mainstay therapy in patients with von Willebrand disease (VWD) unresponsive to desmopressin. There are several commercially available FVIII/VWF concentrates that have been tested in VWD patients. We retrospectively analized the clinical efficacy in bleeding episodes and surgery of a highly purified FVIII/VWF complex with two inactivation steps (Fanhdi) in VWD patients. Sixty patients were included in the study. Treatment schedule consisted of one or more doses (standard dose 40 IU/kg body weight of FVIII) of Fanhdi. One hundred and fifty bleeding episodes were treated. These were: 28 serious bleedings; 92 moderate and 30 mild. An excellent clinical efficacy in almost 95% of cases was observed. Fanhdi was administered during 66 surgical procedures (38 major and 28 minor) with an overall efficacy of 98%. Fanhdi a highly purified, doubly virus-inactivated FVIII/VWF concentrate, with a high content of active VWF and an excellent record of clinical safety, is a valid choice in treating VWD.

Restoration of plasma von Willebrand factor deficiency is sufficient to correct thrombus formation after gene therapy for severe von Willebrand disease

OBJECTIVE

Gene therapy for severe von Willebrand disease (vWD) seems an interesting treatment alternative with long-term therapeutic potential. We investigated the feasibility of targeting the liver for ectopic expression of physiologically active von Willebrand factor (vWF).

METHODS AND RESULTS

The capacity of transgene-encoded murine vWF to restore vWF function was studied in a mouse model of severe vWD after liver-specific gene transfer by hydrodynamic injection. By using a hepatocyte-specific alpha1 antitrypsin promoter, a considerably higher and longer-lasting vWF expression was obtained when compared with a cytomegalovirus promoter, reaching maximum vWF plasma levels that are 10+/-1 times higher than the wild-type level. Liver-expressed vWF showed the full range of multimers, including the high molecular weight multimers, and restored factor VIII plasma levels, consistent with correction of the bleeding time 3 but not 7 days after gene transfer. Importantly, transgene encoded plasma vWF restored proper platelet adhesion and aggregation in a FeCl(3) induced thrombosis model.

CONCLUSIONS

High ectopic expression of transgene encoded plasma vWF can be obtained after gene transfer to the liver. Liver-expressed vWF was fully multimerized and able to restore proper platelet plug formation in severe vWD. The liver therefore seems an attractive target for gene therapy for severe vWD.