ST-segment elevation myocardial infarction (STEMI) caused by spontaneous coronary artery dissection (SCAD) in a patient with von Willebrand disease

A postpartum woman in her early 40s, with a history of pre-eclampsia and von Willebrand disease (VWD), presented to the emergency room with chest pain suggestive of an acute coronary syndrome. Initial workup revealed an evolving anterior wall ST-segment elevation myocardial infarction on ECG and elevated cardiac biomarkers, confirming myocardial damage. Point-of-care ultrasound showed apical hypokinesis and coronary angiography revealed a distal dissection of the left anterior descending coronary artery. There was TIMI 3 flow and no evidence of plaque rupture. No percutaneous coronary intervention was performed and the patient was managed conservatively.Fibromuscular dysplasia was ruled out on screening CT angiography. Dual antiplatelet therapy was initiated for an amended course of 3 months given the history of VWD. Our patient had an uncomplicated course in the hospital with a downward trend in their cardiac biomarkers, resolving anterior ST elevation on serial ECGs, and no bleeding complications.

Type 2M/2A von Willebrand disease: a shared phenotype between type 2M and 2A

ABSTRACT

Four variants have been continuously subjected to debate and received different von Willebrand disease (VWD) classifications: p.R1315L, p.R1315C, p.R1374H, and p.R1374C. We chose to comprehensively investigate these variants with full set of VWD tests, protein-modeling predictions and applying structural biology. Patients with p.R1315L, p.R1315C, p.R1374H, and p.R1374C were included. A group with type 2A and 2M was included to better understand similarities and differences. Patients were investigated for phenotypic assays and underlying disease mechanisms. We applied deep protein modeling predictions and structural biology to elucidate the causative effects of variants. Forty-three patients with these variants and 70 with 2A (n = 35) or 2M (n = 35) were studied. Patients with p.R1315L, p.R1374H, or p.R1374C showed a common phenotype between 2M and 2A using von Willebrand factor (VWF):GPIbR/VWF:Ag and VWF:CB/VWF:Ag ratios and VWF multimeric profile, whereas p.R1315C represented a type 2M phenotype. There was an overall reduced VWF synthesis or secretion in 2M and cases with p.R1315L, p.R1374H, and p.R1374C, but not in 2A. Reduced VWF survival was observed in most 2A (77%), 2M (80%), and all 40 cases with p.R1315L, p.R1374H, and p.R1374C. These were the only variants that fall at the interface between the A1-A2 domains. p.R1315L/C mutants induce more compactness and internal mobility, whereas p.R1374H/C display a more extended overall geometry. We propose a new classification of type 2M/2A for p.R1315L, p.R1374H, and p.R1374C because they share a common phenotype with 2M and 2A. Our structural analysis shows the unique location of these variants on the A1-A2 domains and their distinctive effect on VWF.

Type 1 VWD classification revisited: novel insights from combined analysis of the LoVIC and WiN studies

ABSTRACT

There is significant ongoing debate regarding type 1 von Willebrand disease (VWD) defintion. Previous guidelines recommended patients with von Willebrand factor (VWF) levels <30 IU/dL be diagnosed type 1 VWD, whereas patients with significant bleeding and VWF levels from 30 to 50 IU/dL be diagnosed with low VWF. To elucidate the relationship between type 1 VWD and low VWF in the context of age-induced increases in VWF levels, we combined data sets from 2 national cohort studies: 162 patients with low VWF from the Low VWF in Ireland Cohort (LoVIC) and 403 patients with type 1 VWD from the Willebrand in The Netherlands (WiN) studies. In 47% of type 1 VWD participants, VWF levels remained <30 IU/dL despite increasing age. Conversely, VWF levels increased to the low VWF range (30-50 IU/dL) in 30% and normalized (>50 IU/dL) in 23% of type 1 VWD cases. Crucially, absolute VWF antigen (VWF:Ag) levels and increase of VWF:Ag per year overlapped between low VWF and normalized type 1 VWD participants. Moreover, multiple regression analysis demonstrated that VWF:Ag levels in low VWF and normalized type 1 VWD patients would not have been different had they been diagnosed at the same age (β = 0.00; 95% confidence interval, -0.03 to 0.04). Consistently, no difference was found in the prevalence of VWF sequence variants; factor VIII activity/VWF:Ag or VWF propeptide/VWF:Ag ratios; or desmopressin responses between low VWF and normalized type 1 VWD patients. In conclusion, our findings demonstrate that low VWF does not constitute a discrete clinical or pathological entity. Rather, it is part of an age-dependent type 1 VWD evolving phenotype. Collectively, these data have important implications for future VWD classification criteria.

Evaluation of a diagnostic platelet aggregation test strategy for platelet rich plasma samples with low platelet counts

INTRODUCTION

Light transmission aggregometry (LTA) is important for diagnosing platelet function disorders (PFD) and von Willebrand disease (VWD) affecting ristocetin-induced platelet aggregation (RIPA). Nonetheless, data is lacking on the utility of LTA for investigating thrombocytopenic patients and platelet rich plasma samples with low platelet counts (L-PRP). Previously, we developed a strategy for diagnostic LTA assessment of L-PRP that included: (1) acceptance of referrals/samples, regardless of thrombocytopenia severity, (2) tailored agonist selection, based on which are informative for L-PRP with mildly or severely low platelet counts, and (3) interpretation of maximal aggregation (MA) using regression-derived 95% confidence intervals, determined for diluted control L-PRP (C-L-PRP).

METHODS

To further evaluate the L-PRP LTA strategy, we evaluated findings for a subsequent patient cohort.

RESULTS

Between 2008 and 2021, the L-PRP strategy was applied to 211 samples (11.7% of all LTA samples) from 192 unique patients, whose platelet counts (median [range] × 109 /L) for blood and L-PRP were: 105 [13-282; 89% with thrombocytopenia] and 164 [17-249], respectively. Patient-L-PRP had more abnormal MA findings than simultaneously tested C-L-PRP (p-values <0.001). Among patients with accessible electronic medical records (n = 181), L-PRP LTA uncovered significant aggregation abnormalities in 45 (24.9%), including 18/30 (60%) with <80 × 109  platelets/L L-PRP, and ruled out PFD, and VWD affecting RIPA, in others. The L-PRP LTA strategy helped diagnose VWD affecting RIPA, Bernard Soulier syndrome, familial platelet disorder with myeloid malignancy, suspected ITGA2B/ITGB3-related thrombocytopenia, and acquired PFD.

CONCLUSION

Diagnostic LTA with L-PRP, using a strategy that considers thrombocytopenia severity, is feasible and informative.

Diagnosis and treatment of von Willebrand disease in 2024 and beyond

MANUSCRIPT BACKGROUND AND AIM

The diagnosis and clinical care of patients with von Willebrand disease (VWD) has continued to evolve since the characterization of the von Willebrand factor (VWF) gene in 1985. This condition is almost certainly the most common inherited bleeding disorder, and the major symptomatic burden of the disease is experienced by females during their reproductive years. Diagnosis relies on the identification of a personal and family history of excessive mucocutaneous bleeding, and laboratory features consistent with quantitative and/or qualitative abnormalities of VWF. This review focuses on three aspects of VWD management, with current updates and a look into the future.

MANUSCRIPT THEMES

First, we will address the role of genetics in the diagnosis and possible therapies for VWD. With current technologies, VWD genetic diagnosis is usually confined to the confirmation of type 2 subtypes of the disease and type 3 VWD analysis for family planning. While type 3 VWD is a potential candidate for the application of gene therapy, no treatments are currently close to entering the clinic. Second, the peri-procedural management of patients with VWD remains an important element of care. The choice of product, its dose and schedule all require careful consideration depending upon the type and disruptive nature of the planned procedure. Lastly, in addition to gene therapy, several other novel therapeutic interventions are also being developed for bleeding and prophylaxis in VWD. These include a VWF aptamer interfering with VWF clearance and bioengineered forms of VWF.

Diagnosis and treatment challenges in lower resource countries: State-of-the-art

The 2022 World Federation of Haemophilia Annual Global Survey (AGS) reports that 454,690 patients with inherited bleeding disorders (IBD) have been identified globally. While this represents noteworthy progress, haemophilia epidemiology data indicate that 75% of people with inherited bleeding disorders living in low-income and low-to-middle-income countries have yet to be diagnosed. The AGS also revealed that 11 billion clotting factor units are available to treat haemophilia A and B globally. Due to a lack of finance, these treatments are unavailable to haemophilia in low-income countries with a consequence lack of access equity for haemophilia treatment in these communities. This sobering reality is not limited to haemophilia but applies to von Willebrand Disease (VWD). While VWD is the most prevalent IBD, only 103,844 people living with this condition have been diagnosed globally. Of the diagnosed patients, only a fraction live in low- or middle-income countries. Moreover, the majority of VWD patients are still treated sub-optimally without replacement therapies or prophylaxis, both of which are now accepted as global standards of care. In this state-of-the-art review, the authors reflect on three issues. First, the minimum elements required to diagnose haemophilia in a resource-constrained setting are identified. Second, this review points to the critical stakeholders and outlines their roles in removing access to haemophilia treatment barriers. Finally, the authors examine von Willebrand disease's ongoing diagnostic and treatment challenges and compare these to haemophilia. With the rapidly evolving novel therapies, the therapeutic landscape of all IBD will likely change for the better.

Clinical relevance of genetic variants in the von Willebrand factor according to in-silico methods

Clinical interpretation of genetic variants in the context of the patient's phenotype is a time-consuming and costly process. In-silico analysis using in-silico prediction tools, and molecular modeling have been developed to predict the influence of genetic variants on the quality and/or quantity of the resulting translated protein, and in this way, to alert clinicians of disease likelihood in the absence of previous evidence. Our objectives were to evaluate the success rate of the in-silico analysis in predicting the disease-causing variants as pathogenic and the single-nucleotide variants as neutral, and to establish the reliability of in-silico analysis for determining pathogenicity or neutrality of von Willebrand factor gene-associated genetic variants. Using in-silico analysis, we studied pathogenicity in 31 disease-causing variants, and neutrality in 61 single-nucleotide variants from patients previously diagnosed as type 2 von Willebrand disease. Disease-causing variants and non-synonymous single-nucleotide variants were explored by in-silico tools that analyze the amino acidic sequence. Intronic and synonymous single-nucleotide variants were analyzed by in-silico methods that evaluate the nucleotidic sequence. We found a consistent agreement between predictions achieved by in-silico prediction tools and molecular modeling, both for defining the pathogenicity of disease-causing variants and the neutrality of single-nucleotide variants. Based on our results, the in-silico analysis would help to define the pathogenicity or neutrality in novel genetic variants observed in patients with clinical and laboratory phenotypes suggestive of von Willebrand disease.

The common VWF variant p.Y1584C: detailed pathogenic examination of an enigmatic sequence change

BACKGROUND

As knowledge of the human genome has advanced, so too has the recognition that interpretation of the pathogenic nature of sequence variants can be challenging. The von Willebrand factor (VWF) gene exhibits a significant degree of sequence variability, and the first VWF variant associated with type 1 von Willebrand disease (VWD), c.4751 A>G, p.Y1584C, was described in 2003. However, since that time, the pathogenic nature of this variant has remained unclear, being assigned properties ranging from a risk factor to a pathogenic variant.

OBJECTIVES

To provide additional evaluation on the interpretation of pathogenicity for this common VWF variant.

METHODS

Fifty-eight subjects with only the p.Y1584C variant were recruited from 2 cohort studies (the Zimmerman Program and the Canadian type 1 VWD study). Clinical and laboratory phenotypes were assessed.

RESULTS

The prevalence of the p.Y1584C variant in our cohorts was 23- to 27-fold higher than that in large normal population databases. Significantly more p.Y1584C subjects had an abnormal bleeding score when compared to Y1584 individuals. In comparison with a group of 35 subjects without the p.Y1584C variant, subjects with the variant had lower mean VWF:antigen and VWF:ristocetin cofactor values and significantly higher VWF propeptide/VWF:antigen ratios suggestive of enhanced clearance.

CONCLUSION

Collectively, the results of this analysis suggest that p.Y1584C is likely pathogenic, however, due to influences such as incomplete penetrance, variable expressivity, and other genetic modifiers like ABO blood group, the straightforward assignment of pathogenicity to this variant is inevitably challenging.

von Willebrand disease: A guide for the internist

von Willebrand disease (VWD), the most common inherited bleeding disorder, results when patients either do not make enough von Willebrand factor (VWF) or make defective VWF. The pathophysiology of this disorder is complex but needs to be understood to interpret the diagnostic tests. Most patients have mild to moderate symptoms and can be adequately counseled and managed by a general internist, but some need to consult a hematologist. We review the pathophysiology of VWD, its subtypes, common presentations of each subtype, diagnostic testing, and management of mild as well as severe clinical manifestations of VWD.

A Compound Heterozygosis of Two Novel Mutations in vWF Exacerbates vWD in a Chinese Pedigree

BACKGROUND

von Willebrand disease (vWD), caused by mutations in the von Willebrand factor (vWF) coding gene, is a disease characterized by abnormal coagulation activity and a severe tendency for hemorrhage. Therefore, identifying mutations in vWF is important for diagnosing congenital vWD.

METHODS

We studied a 23-year-old male vWD patient and his parents. Clotting methods were used to determine activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen (FIB) levels, FVIII activity. Chromogenic substrate method was used to determine vWF antigen and activity. The platelet count was determined. Mutations were searched using whole-exome sequencing and certified by Sanger sequencing. Clinical data, including activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen levels, FX activity, FX antigen levels, and the platelet count were collected. A mixing study was performed to eliminate the presence of coagulation factor inhibitors and lupus anticoagulants. Mutations were screened by using whole-exome sequencing (WES) and were verified by using Sanger sequencing.

RESULTS

The proband showed severely decreased vWF antigen, vWF activity, and FVIII activity. RIPA (RISTO-CETIN-induced platelet aggregation) was 0%. Data from WES showed that the proband carried compound heterozygous variants vWF: NM_000552.5 (c.3213C>A p.Cys1071Ter) and vWF: NM_000552.5 (c.6598+2T>C). The proband's mother carried variant vWF: NM_000552.5 (c.3213C>A p.Cys1071Ter) while the proband's father carried variant vWF: NM_000552.5 (c.6598+2T>C). All laboratory test indexes of the proband's parents, including vWF antigen, vWF activity, and FVIII activity, were within the normal ranges.

CONCLUSIONS

We identified a compound heterozygosis with two novel mutations in vWF (c.3213C>A, c.6598+2T >C) in a family pedigree, and our results demonstrate that the compound heterozygous mutations probably exacerbate vWD.

The Role of the von Willebrand Factor Collagen-Binding Assay (VWF:CB) in the Diagnosis and Treatment of von Willebrand Disease (VWD) and Way Beyond: A Comprehensive 36-Year History

The von Willebrand factor (VWF) collagen binding (VWF:CB) assay was first reported for use in von Willebrand diagnostics in 1986, by Brown and Bosak. Since then, the VWF:CB has continued to be used to help diagnose von Willebrand disease (VWD) (correctly) and also to help assign the correct subtype, as well as to assist in the monitoring of VWD therapy, especially desmopressin (DDAVP). However, it is important to recognize that the specific value of any VWF:CB is predicated on the use of an optimized VWF:CB, and that not all VWF:CB assays are so optimized. There are some good commercial assays available, but there are also some "not-so-good" commercial assays available, and these may continue to give the VWF:CB "a bad reputation." In addition to VWD diagnosis and management, the VWF:CB found purpose in a variety of other applications, from assessing ADAMTS13 activity, to investigation into acquired von Willebrand syndrome (especially as associated with use of mechanical circulatory support or cardiac assist devices), to assessment of VWF activity in disease states in where an excess of high-molecular-weight VWF may accumulate, and lead to increased (micro)thrombosis risk (e.g., coronavirus disease 2019, thrombotic thrombocytopenic purpura). The VWF:CB turns 37 in 2023. This review is a celebration of the utility of the VWF:CB over this nearly 40-year history.

Acquired von Willebrand's Syndrome in a Patient with Concomitant Chronic Lymphocytic Lymphoma and Smoldering Multiple Myeloma

An African-American female in her sixties presented to the hospital with intermittent gum bleeding for the past two years along with severe anemia. This case details the differential and workup that lead to the diagnosis of acquired von Willebrand's syndrome (AvWS). A thorough investigation in the possible etiologies of AvWS revealed that the patient had concomitant chronic lymphocytic lymphoma (CLL) and smoldering multiple myeloma (SMM). Due to the concomitant diagnosis of CLL and SMM, there was a dilemma regarding whether CLL, SMM, or both was driving this patient's AvWS. Decision was made to treat the underlying CLL initially with rituximab and later on at recurrence with obinutuzumab/venetoclax with complete resolution of patient's bleeding and normalization of her factor VIII activity, von Willebrand factor antigen levels, and vWF:ristocetin cofactor levels. We believe this is first case in the literature of a patient with AvWS with concurrent CLL and SMM.

Patient-specific severity of von Willebrand factor degradation identifies patients with a left ventricular assist device at high risk for bleeding

BACKGROUND

Continuous-flow left ventricular assist devices (LVADs) cause an acquired von Willebrand factor (VWF) deficiency and bleeding. Models to risk-stratify for bleeding are urgently needed. We developed a model of continuous-flow LVAD bleeding risk from patient-specific severity of VWF degradation.

METHODS

In a prospective, longitudinal cohort study, paired blood samples were obtained from patients (n = 67) with a continuous-flow LVAD before and during support. After 640 ± 395 days, patients were categorized as all-cause bleeders, gastrointestinal (GI) bleeders, or nonbleeders. VWF multimers and VWF clotting function were evaluated to determine bleeding risk.

RESULTS

Of 67 patients, 34 (51%) experienced bleeding, 26 (39%) experienced GI bleeding, and 33 (49%) did not bleed. In all patients, LVAD support significantly reduced high-molecular-weight VWF multimers (P < .001). Bleeders exhibited greater loss of high-molecular-weight VWF multimers (mean ± standard deviation, -10 ± 5% vs -7 ± 4%, P = .008) and reduced VWF clotting function versus nonbleeders (median [interquartile range], -12% [-31% to 4%] vs 0% [-9 to 26%], P = .01). A combined metric of VWF multimers and VWF function generated the All-Cause Bleeding Risk Score, which stratified bleeders versus nonbleeders (86 ± 56% vs 41 ± 48%, P < .001) with a positive predictive value of 86% (95% confidence interval, 66%-95%) and diagnostic odds ratio of 11 (95% confidence interval, 2.9-44). A separate GI Bleeding Risk Score stratified GI bleeders versus nonbleeders (202 ± 114 vs 120 ± 86, P = .003) with a positive predictive value of 88% (64%-97%) and diagnostic odds ratio of 18 (3.1-140).

CONCLUSIONS

The severity of loss of VWF multimers and VWF clotting function generated Bleeding Risk Scores with high predictive value for LVAD-associated bleeding. This model may guide personalized antithrombotic therapy and patient surveillance.

Key Drivers of Coagulation Factor Use in Von Willebrand Disease During Hospitalization: An Overview of the French BERHLINGO Cohort

BACKGROUND

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. However, studies of hospitalisation patterns with replacement treatment are scarce.

OBJECTIVES

The aim of this study was to investigate the current therapeutic management of VWD and determine the key drivers of coagulation factor uses in patients during hospitalisation.

METHODS

Hopscotch-WILL was a multi-centric retrospective study conducted over a 48-month period in any patients with VWD. The data were collected from the BERHLINGO Research Database and the French Hospital database.

RESULTS

A total of 988 patients were included; 153 patients (15%) were hospitalised during 293 stays requiring treatment with von Willebrand factor (VWF) concentrates-pure or in association with Factor VIII (FVIII). Their median basal concentrations of VWF and FVIII were significantly lower than in untreated patients: VWF antigen < 30 IU/dL, VWF activity < 20 IU/dL and FVIII:C < 40 IU/dL. The median (interquartile range) concentrate consumption was similar between highly purified VWF or VWF combined with FVIII (72 [110] vs 57 [89] IU/kg/stay, p = 0.154). The use of VWF was highly heterogeneous by VWD type; type 3 had a particularly high impact on VWF consumption in non-surgical situations. The main admissions were for ear/nose/throat, hepato-gastroenterology, and trauma/orthopaedic conditions, besides gynaecological-obstetric causes in women.

CONCLUSIONS

The use of VWF concentrates is mostly influenced by low basal levels of VWF and FVIII, but also by VWD type or the cause for hospitalisation. These results could inform future studies of newly released recombinant VWF.

Von Willebrand Factor (VWF) multiplex activity assay differentiation of type 1 von Willebrand Disease (VWD) and variant VWD

INTRODUCTION

VWD diagnosis is challenging requiring multiple VWF activity tests using many individual assays. We have developed an ELISA-based VWF Multiplex Activity Assay (VWF-MAA) to address this concern; however, the ability of the VWF-MAA to discriminate between type 1 VWD, variant VWD, and normal subjects has not been evaluated.

AIM

To evaluate the VWF-MAA and its ability to differentiate between type 1 VWD, variant VWD and normal subjects in individuals undergoing an initial laboratory evaluation for bleeding.

METHODS

A total of 177 plasma samples from the Zimmerman Program: Comparative Effectiveness in the Diagnosis of VWD were evaluated from 11 centres across the US and Canada. The VWF-MAA was compared to Versiti Blood Research Institute (VBRI) and Local Center (LC) assigned VWD diagnosis.

RESULTS

Overall, 129/177 (72.9%) were correctly assigned as normal (non-VWD), type 1, or variant VWD compared to the VBRI assigned diagnosis. VWF-MAA assigned non-VWD accurately in 29/57 (50.9%) samples, and type 1 VWD accurately in 93/110 (84.6%) samples. Considering LC diagnosis where there was agreement with VWF-MAA and not VBRI diagnosis, type 1 VWD was accurate in 105/110 (95.5%) samples. Bland-Altman analysis demonstrated good correlation between laboratory methods. VWD, types 2A, 2B, 1C VWD were also assigned by the VWF-MAA.

CONCLUSIONS

We demonstrate that the VWF-MAA has utility in differentiating type 1 VWD, variant VWD and normal subjects in individuals undergoing an initial laboratory evaluation for bleeding.

Management of pregnant women who have bleeding disorders

Bleeding disorders, including von Willebrand disease (VWD), hemophilia, other coagulation factor deficiencies, platelet disorders, defects of fibrinolysis, and connective tissue disorders, have both maternal and fetal implications. Successful management of bleeding disorders in pregnant women requires not only an understanding of bleeding disorders but also an understanding of when and how bleeding occurs in pregnancy. Bleeding does not occur during a normal pregnancy with a healthy placenta. Bleeding occurs during pregnancy when there is an interruption of the normal utero-placental interface, during miscarriage, during an ectopic pregnancy, or at the time of placental separation at the conclusion of pregnancy. Although mild platelet defects may be more prevalent, the most commonly diagnosed bleeding disorder among women is VWD. Other bleeding disorders are less common, but hemophilia carriers are unique in that they are at risk of bleeding themselves and of giving birth to an affected male infant. General guidance for maternal management of a woman who is moderately or severely affected includes obtaining coagulation factor levels at a minimum in the third trimester; planning for delivery at a center with hemostasis expertise; and anticipating the need for hemostatic agents. General guidance for fetal management includes pre-pregnancy counseling; the option of preimplantation genetic testing for hemophilia; delivery at a tertiary care center with pediatric hematology and newborn intensive care; consideration of cesarean delivery of a potentially severely affected infant; and avoidance of invasive procedures such as scalp electrodes and operative vaginal delivery in any potentially affected infant.

Surprise diagnosis of acquired von Willebrand syndrome in a patient previously thought to have type III von Willebrand disease: evaluation and periprocedural management

Acquired von Willebrand syndrome (AVWS) is a rare disorder that is characterised by an acquired deficiency of von Willebrand factor. AVWS was suspected in a patient with type III von Willebrand disease (VWD) who did not respond to factor replacement therapy. Given the crucial implications for management, we describe this patient's clinical presentation, diagnosis and periprocedural management. To facilitate pericardiocentesis, periprocedural management included steroids, intravenous immunoglobulin and factor replacement therapy. In other patients with suspected immune-mediated AVWS, a similar approach may be effective. This case also highlights the importance of distinguishing AVWS from inherited VWD.

Acquired von Willebrand disease in children undergoing extracorporeal membrane oxygenation: a prospective observational study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) provides cardiopulmonary support for children with severe cardiac and/or pulmonary failure. The incidence of bleeding complications during ECMO support is high. Acquired von Willebrand disease (AVWD) might contribute to the development of bleeding complications.

OBJECTIVE

To study the incidence and longitudinal profile of AVWD during the first 14 days of ECMO support in children and to investigate the association between AVWD and bleeding complications.

METHODS

This prospective observational study included pediatric patients (0-17 years) receiving ECMO. Blood was sampled prior to and after ECMO start, daily and 12 to 24 hours after stopping ECMO. von Willebrand factor (VWF) parameters and multimer patterns were determined. Clinical data were collected for each patient. AVWD was defined as loss of high-molecular weight multimers (ie, decreased compared with baseline) or a VWF:collagen binding/VWF: antigen (Ag) ratio or VWF:activity/VWF:Ag ratio below 0.7.

RESULTS

All of 50 (100%) patients developed AVWD during ECMO. The VWF:collagen binding /VWF:Ag ratio, VWF:activity/VWF:Ag ratio, and high-molecular weight multimers decreased during the initial days and recovered to baseline level within 24 hours after stopping ECMO. The incidence and longitudinal profile of AVWD were similar in patients with and without major bleeding complications.

CONCLUSION

Children receiving ECMO support commonly develop AVWD. AVWD develops rapidly after ECMO initiation and recovers quickly after ECMO cessation. Importantly, AVWD appears to be independent of major bleeding.

A new case of platelet-type von Willebrand disease supports the recent findings of gain-of-function GP1BA variants outside the C-terminal disulphide loop enhances affinity for von Willebrand factor

Platelet-type von Willebrand disease (PT-VWD) is a rare autosomal dominant bleeding disorder characterized by an increased ristocetin-induced platelet aggregation (RIPA) and enhanced affinity of platelet glycoprotein Ibα (GPIbα) to von Willebrand factor (VWF). To date, only seven variants have been described with this gain-of-function effect, most of them located in the C-terminal disulphide loop of the VWF-binding domain of GPIbα. We herein describe a patient with moderate bleeding symptoms, mild thrombocytopenia and increased RIPA. By direct sequencing of GP1BA, a novel leucine-rich repeat heterozygous variant was identified (c.580C>T; predictably p.Leu194Phe), strongly suggestive as being the underlying cause for the PT-VWD phenotype of our patient.

Initial von Willebrand factor antigen values in adolescent females predict future values

INTRODUCTION

Diagnosing von Willebrand Disease (VWD) in adolescent females is challenging as menstruation and physiologic stress elevate von Willebrand factor (VWF) laboratory values.

AIM

To develop a VWF prediction model for adolescent females based on initial VWF results.

METHODS

We identified female patients aged 9 to 21 years with any VWF laboratory test over a 5-year period (2017-2021) at any Texas Children's Hospital facility. Patient demographics, VWF testing, haemoglobin concentration, serum ferritin and site of clinical testing were collected (initial and subsequent laboratory evaluations). A Bayesian linear regression model was developed. Prediction intervals were analysed to identify thresholds for patients in whom repeat testing was unlikely to identify low VWF levels (< 50%), consistent with VWD.

RESULTS

A total of 6125 adolescent females underwent VWF testing; 1204 (19.7%) had repeat testing. Based on the prediction model, initial VWF antigen values of 80%, 90% and ≥100% carried a 92.6%, 96.6% and ≥98.0% probability of having repeat normal repeat VWF values, respectively. Subjects assessed in outpatient adolescent medicine or gynaecology clinics were more likely to have low VWF values compared to those assessed in the acute care setting (p < .001). Median presenting haemoglobin and serum ferritin were 12.4 g/dL and 13 ng/mL, respectively and were similar in those with normal versus low VWF antigen values.

CONCLUSION

Repeat testing in adolescent females whose initial VWF antigen values are ≥90% is unlikely to identify additional patients with VWD. Iron deficiency screening should be performed in all adolescent females.

Bleeding disorder of unknown cause: Results from Iranian study

BACKGROUND

Definite diagnosis of patients with mild to moderate bleeding is challenging. Some studies reported that even more than 50% of their patients remained undiagnosed which is classified as a Bleeding disorder of unknown cause (BDUC). This study aims to document the clinical characteristics and proportion of patients with BDUC in the Iranian Comprehensive Hemophilia Care Center (ICHCC) one of the referral centers for diagnosis of congenital bleeding disorder in Iran.

METHODS

This study was conducted on 397 patients who were referred with a bleeding manifestation to ICHCC from 2019 to 2022. Demographic and laboratory data were documented for all patients. Bleeding questionnaires including ISTH-Bleeding Assessment tool (ISTH-BAT) and the Molecular and Clinical Markers for the Diagnosis and Management of Type 1 (MCMDM-1 (ISTH-BAT, MCMDM-1, and the Pictorial Bleeding Assessment Chart (PBLAC) were filled out for all patients. The data were analyzed by the statistical package for social science (SPSS version 22, SPSS, Chicago, Illinois, USA).

RESULTS

BDUC was diagnosed in 200 patients and 197 patients reached the final diagnosis. Hemophilia, von Willebrand disease (VWD), factor (F) VII deficiency, and platelet functional disorders (PFDs) were confirmed in 54, 49, 34, and 15 of the patients, respectively. No significant difference was found in bleeding scores between patients with BDUC and those with confirmed disease. In contrast, after setting cut-off (ISTH-BAT for males ≥ 4 and females ≥ 6 and MCMDM-1 for males ≥ 3 and females ≥ 5) clinically significant difference was found. There was no association between having a positive consanguineous marriage and setting a diagnosis; however, significant associations were seen for having a positive family history of bleeding. Age (OR =0.977, 95% CI.965-0.989), gender (BDUC female, 151/200; final diagnosis female, 95/197) (OR=3.3, 95% CI 2.16-5.06), family history (OR = 3.19, 95% CI 1.99-5.11), and consanguineous marriage (OR=1.59, 95% CI 1.03-2.45) were considered as a risk factor for categorizing the patients with BDUC or final diagnosis.

CONCLUSION

The findings are mainly in line with previous studies about BDUC patients. The large number of patients with BDUC underlines the incompleteness of available routine laboratory tests and shows the necessity of progress in the development of reliable diagnostic tools to identify underlying bleeding disorders.

Von Willebrand Factor Multimer Analysis and Classification: A Comprehensive Review and Updates

Von Willebrand factor (VWF) is a multimeric glycoprotein with essential roles in primary hemostasis. Patients with von Willebrand disease (VWD), due to quantitative and/or qualitative defects of VWF usually experience mucocutaneous bleeding. Based on the laboratory results of VWF antigen, various VWF activities, factor VIII activity, and VWF multimer patterns, VWD can be categorized as type 1, 2, and 3 VWD. VWF multimer analysis by either manual or semi-automated electrophoresis and immunoblotting is a critical part of the laboratory testing to differentiate type 1, type 2 VWD, and subtypes of type 1 or 2 VWD. The multimer distribution patterns can also help to understand the underlying molecular mechanism of VWF synthesis, multimerization, and clearance defects in VWD. This review will cover VWF synthesis, multimerization, secretion, VWF multimer analysis, and VWF multimer interpretation of various types and subtypes of VWD.

How I approach bleeding in hospitalized patients

Excessive bleeding is relatively common in adult inpatients, whether as the primary reason for admission or as a development during the hospital stay. Common causes include structural issues, medication effects, and systemic illnesses; occasionally, unexpected bleeding can develop as a result of an undiagnosed or newly acquired bleeding disorder. The first step in caring for the inpatient who is bleeding is to determine whether the bleeding symptom is truly new or whether the patient has a history of abnormal bleeding. Patients with a history of abnormal bleeding may warrant evaluation for inherited bleeding disorders, such as platelet function disorders, von Willebrand disease, hemophilia, or rare factor deficiencies. Patients with no history of bleeding, for whom other causes, such as liver dysfunction, medication effect, disseminated intravascular coagulation, or certain vitamin deficiencies have been ruled out may require evaluation for acquired coagulopathies, such as acquired hemophilia or acquired von Willebrand disease. Here, we present 3 cases to discuss the diagnosis and management of the 2 most common acquired bleeding disorders as well as a patient with a congenital bleeding disorder with a historical diagnosis.

Closing the Diagnostic Gap in Adolescents and Young Adult Women With Bleeding Disorders: Missed Opportunities

Approximately 2% of the general population have an underlying inherited bleeding disorder, which, for adolescents and young adult women, has both physical risks and adverse psychosocial effects. Heavy menstrual bleeding can be the first sign of an underlying bleeding disorder such as von Willebrand disease and the X-linked bleeding disorders hemophilia A and B. Connective tissue disorders such as Ehlers-Danlos syndrome, in particular the hypermobile subtype, are relatively frequent in the general population and can also cause bleeding symptoms from impaired hemostasis due to defective collagen. For more than 20 years, the American College of Obstetricians and Gynecologists (ACOG) has recommended screening adolescents and young adult women for bleeding disorders when they present with heavy menstrual bleeding. Despite this directive, there is a significant gap from symptom onset to time of diagnosis in this patient population. We must work to effectively close this diagnostic gap by consistently obtaining thorough bleeding histories, performing the appropriate laboratory evaluations, working collaboratively with hematologists, and using tools and materials promoted by ACOG. Improved screening and earlier diagnosis of these individuals can have far-reaching effects that are not limited to heavy menstrual bleeding management and extend to peripartum considerations and prenatal counseling.

[Preparation and Application of Monoclonal Antibody Against Human von Willebrand Factor Propeptide]

OBJECTIVE

To develop monoclonal antibodies that can specifically recognize human von Willebrand factor (VWF) propeptide (VWFpp) in plasma, and establish a rapid and reliable method for the detection of VWFpp antigen in plasma by using the double-antibody sandwich ELISA with the obtained anti-VWFpp monoclonal antibody.

METHODS

The recombinant human VWFpp (D1 and D2 regions) protein expressed in eukaryotic cells was used as immunogen to immunize BALB/c mice with routine method, so as to obtain clones of fusion cells. After screening and identification, hybridoma cell lines secreting monoclonal antibodies against VWFpp were selected, and then double-antibody sandwich ELISA assay was used to construct VWFpp antigen detection kit for the determination of VWFpp in human plasma. The levels of VWFpp antigen in plasma of 12 leukemia patients who underwent bone marrow transplantation were dynamically detected.

RESULTS

Two hybridoma cell lines that can be subcultured continuously and secrete monoclonal antibodies against VWFpp were obtained and named SZ175 and SZ176 respectively. Identified by ELISA and Western blot, the antibodies could both specifically recognize VWFpp but couldn't recognize mature VWF (without propeptide). Based on the principle of double-antibody sandwich ELISA, monoclonal antibodies SZ175 and SZ176 were successfully made into a kit for detecting VWFpp antigen. The plasma VWFpp levels of leukemia patients before and after bone marrow transplantation were dynamically detected. The results showed that the plasma VWFpp levels of the patients after transplantation were significantly higher than those before transplantation.

CONCLUSION

Two monoclonal antibodies against VWFpp were successfully prepared, and a double-antibody sandwich ELISA detection kit for VWFpp antigen was constructed, which provides a powerful tool for further study on the biological function of VWFpp, the clinical diagnosis and classification of von Willebrand disease (VWD), and the prognostic monitoring of endothelial injury-related diseases.

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.

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.

Patient-centered care in von Willebrand disease: are we there yet?

INTRODUCTION

Von Willebrand Disease is the most common inherited bleeding disorder. Paradoxically, affected individuals are often misdiagnosed and experience substantial diagnostic delay. There are sex-specific health disparities in VWD rooted in the stigmatization of vaginal bleeding, which leads to symptom dismissal, lack of timely access to care and lower health-related quality of life.

AREAS COVERED

Following the core elements of patient-centered care - respect for patient preferences, values, and needs, we describe the current state of VWD care. Challenges of diagnostic delay, serial misrecognition of abnormal bleeding, and symptom dismissal are barriers that disproportionately affect women with VWD. These negative effects are further amplified in individuals living in low- and middle-income countries. We describe the importance of coordinated multidisciplinary care, as well as the need for patient education and empowered self-advocacy.

EXPERT OPINION

While tremendous work has been done to improve the diagnosis and management of VWD, timely and high-quality research is urgently needed to address care gaps. Systemic changes such as resource investment, dedicated research funding for novel treatment modalities, and effective knowledge translation strategies to address structural barriers are needed to facilitate effective patient-centered care for VWD.

von Willebrand factor neutralizing and non-neutralizing alloantibodies in 213 subjects with type 3 von Willebrand disease enrolled in 3WINTERS-IPS

BACKGROUND

Type 3 von Willebrand disease (VWD) is the most severe form of this disease owing to the almost complete deficiency of von Willebrand factor (VWF). Replacement therapy with plasma-derived products containing VWF or recombinant VWF rarely cause the development of alloantibodies against VWF that may be accompanied by anaphylactic reactions.

OBJECTIVE

The objective of this study was to assess the prevalence of anti-VWF alloantibodies in subjects with type 3 VWD enrolled in the 3WINTERS-IPS.

METHODS

An indirect in-house enzyme-linked immunosorbent assay has been used to test all the alloantibodies against VWF. Neutralizing antibodies (inhibitors) have been tested with a Bethesda-based method by using a VWF collagen binding (VWF:CB) assay. Samples positive for anti-VWF antibodies were further tested with Bethesda-based methods by using the semiautomated gain-of-function glycoprotein-Ib binding (VWF:GPIbM) and a VWF antigen (VWF:Ag) enzyme-linked immunosorbent assay.

RESULTS

In total, 18 of the 213 (8.4%) subjects tested positive for anti-VWF antibodies and 13 of 213 (6%) had VWF:CB inhibitors. These 13 were among the 18 with anti-VWF antibodies. Of the 5 without VWF:CB inhibitors, 3 had non-neutralizing antibodies, 1 only inhibitor against VWF:GPIbM, and one could not be tested further. Ten of the 13 subjects with VWF:CB inhibitors also had VWF:GPIbM inhibitors, 6 of whom also had VWF:Ag inhibitors. Subjects with inhibitors were homozygous for VWF null alleles (11/14), homozygous for a missense variant (1/14), or partially characterized (2/14).

CONCLUSIONS

Anti-VWF antibodies were found in 8.4% of subjects with type 3 VWD, whereas neutralizing VWF inhibitors were found in 6%, mainly in subjects homozygous for VWF null alleles. Because inhibitors may be directed toward different VWF epitopes, their detection is dependent on the assay used.

Challenges in the management of women with type 2B von Willebrand disease during pregnancy and the postpartum period: evidence from literature and data from an international registry and physicians' survey-communication from the Scientific and Standardization Committees of the International Society on Thrombosis and Haemostasis

BACKGROUND

Management of women with type 2B von Willebrand disease (VWD) during pregnancy is challenging because of dysfunctional von Willebrand factor (VWF) and the complexity resulting from discrepant VWF/factor VIII (VWF/FVIII) levels, impaired platelet-dependent VWF activity, progressive thrombocytopenia, and risks associated with the use of desmopressin. There is a lack of high-quality evidence to support clinical decision making.

OBJECTIVES

In this study, we examined the current diagnostic and management approaches and outcomes in women with VWD during pregnancy.

METHODS

Data were collected via 3 avenues: literature review, an international registry, and an international survey on physicians' practices for the management of pregnancy in women with VWD. The registry and survey were supported by the International Society on Thrombosis and Haemostasis.

RESULTS

Data on clinical and laboratory features, management and bleeding complications, and pregnancy outcomes of a total of 55 pregnancies from 49 women across the globe (literature: 35, registry: 20) and data reported by 112 physicians were analyzed. We describe the largest dataset on pregnancies in women with type 2B VWD available to date. The data highlight the following key issues: a) bleeding complications remain a concern in these patients, b) the target safe VWF level and the ideal monitoring approach are unknown, c) there is a wide range of hemostatic management practices in the type and timing of treatment, and d) physicians have diverse views on the mode of delivery and use of neuraxial anesthesia.

CONCLUSION

We conclude that an international consensus and guidance are critically required for better care and improved outcomes in this patient cohort.

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.

von Willebrand factor unfolding mediates platelet deposition in a model of high-shear thrombosis

Thrombosis under high-shear conditions is mediated by the mechanosensitive blood glycoprotein von Willebrand factor (vWF). vWF unfolds in response to strong flow gradients and facilitates rapid recruitment of platelets in flowing blood. While the thrombogenic effect of vWF is well recognized, its conformational response in complex flows has largely been omitted from numerical models of thrombosis. We recently presented a continuum model for the unfolding of vWF, where we represented vWF transport and its flow-induced conformational change using convection-diffusion-reaction equations. Here, we incorporate the vWF component into our multi-constituent model of thrombosis, where the local concentration of stretched vWF amplifies the deposition rate of free-flowing platelets and reduces the shear cleaning of deposited platelets. We validate the model using three benchmarks: in vitro model of atherothrombosis, a stagnation point flow, and the PFA-100, a clinical blood test commonly used for screening for von Willebrand disease (vWD). The simulations reproduced the key aspects of vWF-mediated thrombosis observed in these experiments, such as the thrombus location, thrombus growth dynamics, and the effect of blocking platelet-vWF interactions. The PFA-100 simulations closely matched the reported occlusion times for normal blood and several hemostatic deficiencies, namely, thrombocytopenia, vWD type 1, and vWD type 3. Overall, this multi-constituent model of thrombosis enables macro-scale 3D simulations of thrombus formation in complex geometries over a wide range of shear rates and accounts for qualitative and quantitative hemostatic deficiencies in patient blood.

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.

JTH in Clinic - Obstetric bleeding: VWD and other inherited bleeding disorders

Individuals with inherited bleeding disorders (IBDs) have higher bleeding risk during pregnancy, childbirth, and the postpartum period. Clinical management requires recognition of the IBD as high risk for postpartum hemorrhage and a personalized multidisciplinary approach that includes the patient in decision making. When the fetus is known or at risk to inherit a bleeding disorder, fetal and neonatal bleeding risk also need to be considered. In pregnant IBD patients, it is common for providers to need to make decisions in the absence of high level of certainty evidence. We here present the case of a pregnant von Willebrand disease patient that reached multiple decision points where there is currently clinical ambiguity due to a lack of high level of certainty evidence. For each stage of her care, from diagnosis to the postpartum period, we discuss current literature and describe our approach. This is followed by a brief overview of considerations in other IBDs and pregnancy.

Increased cleavage of von Willebrand factor by ADAMTS13 may contribute strongly to acquired von Willebrand syndrome development in patients with essential thrombocythemia

BACKGROUND

Patients with essential thrombocythemia (ET) often experience bleeding associated with acquired von Willebrand syndrome (AVWS) when the platelet count is markedly increased.

OBJECTIVE

We investigated whether von Willebrand factor (VWF) degradation is enhanced in patients with ET.

METHODS

Seventy patients with ET underwent VWF multimer (VWFM) analysis and measurement of VWF-related parameters. We calculated the VWFM index, defined as the ratio of intensities of a patient's molecular weight-categorized VWFMs, and those of a healthy subject's, using densitometric analysis. VWF degradation product (DP) was measured via ELISA using a monoclonal antibody that specifically recognizes Y1605 at the C-terminal boundary, which is exposed following ADAMTS13-mediated cleavage of the Y1605-M1606 bond of the VWF A2 domain.

RESULTS

Patients with higher platelet counts had a significantly reduced high molecular weight (HMW)-VWFM index and an increased VWF-DP:VWF antigen (Ag) ratio compared to those with lower platelet counts. On multivariate analysis, the VWF-DP/VWF:Ag ratio was an independent predictor of the HMW-VWFM index. Patients who underwent cytoreductive therapy had a significantly higher HMW-VWFM index and lower VWF-DP/VWF:Ag ratio than those who did not. Among individual patients, there was also a significant increase in the HMW-VWFM index and a decrease in the VWF-DP/VWF:Ag ratio after cytoreductive therapy compared to pre-therapy values.

CONCLUSION

In patients with ET, an increased platelet count is associated with enhanced cleavage of VWF at the Y1605-M1606 bond, primarily by ADAMTS13, leading to AVWS. Cytoreductive therapy reduces the platelet count, prevents excessive VWF cleavage, and improves VWFM distributions.

Molecular pathogenesis and heterogeneity in type 3 VWD families in U.S. Zimmerman program

BACKGROUND

Type 3 von Willebrand Disease (VWD) is a rare and severe form of VWD characterized by the absence of von Willebrand factor (VWF).

OBJECTIVES

As part of the Zimmerman Program, we sought to explore the molecular pathogenesis, correlate bleeding phenotype and severity, and determine the inheritance pattern found in type 3 VWD families.

PATIENTS/METHODS

62 index cases with a pre-existing diagnosis of type 3 VWD were analyzed. Central testing included FVIII, VWF:Ag, VWF:RCo, and VWFpp. Bleeding symptoms were quantified using the ISTH bleeding score. Genetic analysis included VWF sequencing, comparative genomic hybridization and predictive computational programs.

RESULTS

75% of subjects (46) had central testing confirming type 3, while 25% were re-classified as type 1-Severe or type 1C. Candidate VWF variants were found in all subjects with 93% of expected alleles identified. The majority were null alleles including frameshift, nonsense, splice site, and large deletions, while 13% were missense variants. Additional studies on 119 family members, including 69 obligate carriers, revealed a wide range of heterogeneity in VWF levels and bleeding scores, even amongst those with the same variant. Co-dominant inheritance was present in 51% of families and recessive in 21%, however 28% were ambiguous.

CONCLUSION

This report represents a large cohort of VWD families in the U.S. with extensive phenotypic and genotypic data. While co-dominant inheritance was seen in approximately 50% of families, this study highlights the complexity of VWF genetics due to the heterogeneity found in both VWF levels and bleeding tendencies amongst families with type 3 VWD.

Von Willebrand factor propeptide and pathophysiological mechanisms in European and Iranian patients with type 3 von Willebrand disease enrolled in the 3WINTERS-IPS study

BACKGROUND

Type 3 von Willebrand disease (VWD) is a severe bleeding disorder caused by the virtually complete absence of von Willebrand factor (VWF). Pathophysiological mechanisms of VWD like defective synthesis, secretion, and clearance of VWF have previously been evaluated using ratios of VWF propeptide (VWFpp) over VWF antigen (VWF:Ag) and factor (F)VIII coagulant activity (FVIII:C) over VWF:Ag.

OBJECTIVE

To investigate whether the VWFpp/VWF:Ag and FVIII:C/VWF:Ag ratios may also be applied to understand the pathophysiological mechanism underlying type 3 VWD and whether VWFpp is associated with bleeding severity.

METHODS

European and Iranian type 3 patients were enrolled in the 3WINTERS-IPS study. Plasma samples and buffy coats were collected and a bleeding assessment tool was administered at enrolment. VWF:Ag, VWFpp, FVIII:C, and genetic analyses were performed centrally, to confirm patients' diagnoses. VWFpp/VWF:Ag and FVIII:C/VWF:Ag ratios were compared among different variant classes using the Mann-Whitney test. Median differences with 95% confidence intervals (CI) were estimated using the Hodges-Lehmann method. VWFpp association with bleeding symptoms was assessed using Spearman's rank correlation.

RESULTS

Homozygosity/compound heterozygosity for missense variants showed higher VWFpp level and VWFpp/VWF:Ag ratio than homozygosity/compound heterozygosity for null variants ([VWFpp median difference, 1.4 IU/dl; 95% CI, 0.2-2.7; P = .016]; [VWFpp/VWF:Ag median difference, 1.4; 95% CI, 0-4.2; P = .054]).

FVIII

C/VWF:Ag ratio was similarly increased in both. VWFpp level did not correlate with the bleeding symptoms (r = .024; P = .778).

CONCLUSIONS

An increased VWFpp/VWF:Ag ratio is indicative of missense variants, whereas FVIII:C/VWF:Ag ratio does not discriminate missense from null alleles. The VWFpp level was not associated with the severity of bleeding phenotype.

Reevaluation of von Willebrand disease diagnosis in a Croatian paediatric cohort combining bleeding scores, phenotypic laboratory assays and next generation sequencing: a pilot study

Introduction

This study reevaluated von Willebrand disease (vWD) diagnosis in a Croatian paediatric cohort by combining bleeding scores (BS), phenotypic laboratory testing, and next-generation sequencing (NGS).

Materials and methods

A total of 25 children (11 males and 14 females, median age 10 years, from 2 to 17) previously diagnosed with vWD were included. BS were calculated using an online bleeding assessment tool. Phenotypic laboratory analyses included platelet count, platelet function analyser closure times, prothrombin time, activated partial thromboplastin time, von Willebrand factor antigen (vWF:Ag), vWF gain-of-function mutant glycoprotein Ib binding activity (vWF:GPIbM), vWF collagen binding activity (vWF:CBA), factor VIII activity (FVIII:C) and multimeric analysis. Next-generation sequencing covered regions of both vWF and FVIII genes and was performed on MiSeq (Illumina, San Diego, USA).

Results

Disease-associated variants identified in 15 patients comprised 11 distinct heterozygous vWF gene variants in 13 patients and one novel FVIII gene variant (p.Glu2085Lys) in two male siblings. Four vWF variants were novel (p.Gln499Pro, p.Asp1277Tyr, p.Asp1277His, p.Lys1491Glu). Three patients without distinctive variants had vWF:GPIbM between 30 and 50%. Patients with identified vWF gene variants had statistically significant lower values of vWF:GPIbM (P = 0.002), vWF:Ag (P = 0.007), vWF:CBA (P < 0.001) and FVIII:C (P = 0.002), compared to those without. Correlations between BS and phenotypic laboratory test results were not statistically significant for either of the tests.

Conclusion

The applied diagnostic approach confirmed the diagnosis of vWD in 13 patients and mild haemophilia A in two. Limited utility of BS in the paediatric population was evidenced.

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.

Distinct Mechanisms of IgM-Antibody-Mediated Acquired von Willebrand Syndrome and Successful Treatment with Recombinant von Willebrand Factor in One Patient

Acquired von Willebrand Syndrome (AVWS) is a rare coagulation disorder which can be associated with IgM paraproteinaemia. Recently, recombinant von Willebrand factor (rVWF) has become available for the treatment of bleedings in patients with inherited von Willebrand disease, but experience in patients with AVWS is limited. We report on 2 patients with AVWS with underlying IgM paraproteinaemia with distinct underlying pathomechanisms. In 1 patient, the paraprotein built unspecific complexes with von Willebrand factor (VWF). In the other patient, we were able to detect an IgM antibody against VWF. Bleeding in this patient was successfully treated with rVWF. To our knowledge, this is the first report about the successful use of rVWF in a patient with AVWS with the detection of a VWF-specific antibody.