Heyde's syndrome: a challenging case of severe aortic stenosis and gastrointestinal bleeding

We present the case of an elderly man with a history of diastolic congestive heart failure, severe aortic stenosis and atrial fibrillation, who presented with fatigue, weakness, coffee ground emesis and black tarry stool. Haemoglobin was 68 g/L. Lactate dehydrogenase was elevated at 1038. Evaluation by cardiology and gastroenterology specialists revealed reflux oesophagitis and a mild hiatal hernia on oesophagogastroduodenoscopy, normal colonoscopy and small bowel series without obstruction. Capsule endoscopy identified angiodysplasia in the small intestine.The patient was diagnosed with Heyde's syndrome based on the triad of severe aortic stenosis, gastrointestinal bleeding from angiodysplasia and acquired von Willebrand syndrome. The patient underwent transcatheter aortic valve replacement, resulting in the resolution of symptoms.Heyde's syndrome represents a challenging clinical entity requiring a multidisciplinary approach for accurate diagnosis and management. Early recognition, prompt intervention and interdisciplinary collaboration are crucial in optimising patient outcomes.

Impact of allele-selective silencing of von Willebrand factor in mice based on a single nucleotide allelic difference in von Willebrand factor

INTRODUCTION

Von Willebrand factor (VWF) plays a pathophysiological role in hemostatic disorders. Partial inhibition of the VWF gene through small interfering RNA (siRNA)-mediated allele-selective silencing could be a promising therapeutic strategy. For von Willebrand disease, allele-selectively inhibiting dominant-negative VWF-alleles might ameliorate the phenotype. For thrombotic disorders, partial VWF reduction can lower thrombotic risk, while avoiding bleeding. Previously, we demonstrated the feasibility of Vwf-silencing in homozygous C57BL/6J (B6) or 129S1/SvImJ (129S) mice. The present study investigated allele-selective Vwf-silencing in a complex heterozygous setting of crossed B6 and 129S mice and its subsequent hemostatic impact.

MATERIALS AND METHODS

Heterozygous B6.129S mice were treated with siRNAs targeting Vwf expressed from either B6- (siVwf.B6) or 129S-alleles (siVwf.129S). Plasma VWF and lung Vwf mRNA were determined. siVwf.B6-treated B6.129S mice were subjected to ferric chloride-induced mesenteric vessel thrombosis and tail-bleeding.

RESULTS

In B6.129S mice, siVwf.B6 reduced Vwf mRNA of the targeted B6-allele by 72% vs. only 12% of the non-targeted 129S-allele (41% total mRNA reduction), lowering plasma VWF by 46%. Oppositely, siVwf.129S reduced Vwf mRNA by 45%, now selectively inhibiting the 129S-allele over the B6-allele (58% vs. 9%), decreasing plasma VWF by 43%. The allele-selective VWF reduction by siVwf.B6 coincided with decreased thrombus formation in mesenteric arterioles, without prolonging tail-bleeding times.

CONCLUSIONS

This study demonstrates the feasibility of allele-selective Vwf-silencing in a heterozygous setting, achieving a controlled close to 50% reduction of plasma VWF. The observed thromboprotection and absence of prolonged bleeding times underline the potential of allele-selective Vwf-silencing as a therapeutic strategy in hemostatic disorders.

A noncanonical splicing variant c.875-5 T > G in von Willebrand factor causes in-frame exon skipping and type 2A von Willebrand disease

INTRODUCTION

A novel variant involving noncanonical splicing acceptor site (c.875-5 T > G) in propeptide coding region of von Willebrand factor (VWF) was identified in a patient with type 2A von Willebrand disease (VWD), who co-inherited with a null variant (p.Tyr271*) and presented characteristic discrepancy of plasma level of VWF antigen and activity, and a selective reduction of both intermediate-molecular-weight (IMWMs) and high-molecular-weight VWF multimers (HMWMs).

MATERIALS AND METHODS

VWF mRNA transcripts obtained from peripheral leukocytes and platelets of the patients were investigated to analyze the consequence of c.875-5 T > G on splicing. The impact of the variant on expression and multimer assembly was further analyzed by in vitro expression studies in AtT-20 cells. The intracellular processing of VWF mutant and the Weibel-Palade bodies (WPBs) formation was evaluated by immunofluorescence staining and electron microscopy.

RESULTS

The mRNA transcript analysis revealed that c.875-5 T > G variant led to exon 8 skipping and an in-frame deletion of 41 amino acids in the D1 domain of VWF (p.Ser292_Glu333delinsLys), yielding a truncated propeptide. Consistent with the patient's laboratory manifestations, the AtT-20 cells transfected with mutant secreted less VWF, with the VWF antigen level in conditioned medium 47 % of wild-type. A slight retention in the endoplasmic reticulum was observed for the mutant. Almost complete loss of IMWMs and HMWMs in the medium and impaired WPBs formation in the cell, indicating truncated VWF propeptide lost its chaperon-like function for VWF multimerization and tubular storage.

CONCLUSIONS

The VWF splicing site variant (c.875-5 T > G) causes propeptide truncation, severely compromising VWF multimer assembly and tubular storage.

Clusterin knockdown has effects on intracellular and secreted von Willebrand factor in human umbilical vein endothelial cells

Alterations in von Willebrand factor (VWF) have an important role in human health and disease. Deficiency of VWF is associated with symptoms of bleeding and excesses of VWF are associated with thrombotic outcomes. Understanding the mechanisms that drive VWF regulation can lead to a better understanding of modulation of VWF levels in humans. We identified clusterin (CLU) as a potential candidate regulator of VWF based on a single cell RNA sequencing (scRNA-seq) analysis in control endothelial cells (ECs) and von Willebrand disease (VWD) endothelial colony-forming-cells (ECFCs). We found that patients with deficiencies of VWF (von Willebrand disease, VWD) had decreased CLU expression and ECs with low VWF expression also had low CLU expression. Based on these findings, we sought to evaluate the role of CLU in the regulation of VWF, specifically as it relates to VWD. As CLU is primarily thought to be a golgi protein involved in protein chaperoning, we hypothesized that knockdown of CLU would lead to decreases in VWF and alterations in Weibel-Palade bodies (WPBs). We used both siRNA- and CRISPR-Cas9-based approaches to modulate CLU in human umbilical vein endothelial cells (HUVECs) and evaluated VWF protein levels, VWF mRNA copy number, and WPB quantity and size. We demonstrated that siRNA-based knockdown of CLU resulted in decreases in VWF content in cellular lysates and supernatants, but no significant change in WPB quantity or size. A CRISPR-Cas9-based knockdown of CLU demonstrated similar findings of decreases in intracellular VWF content but no significant change in WPB quantity or size. Our data suggests that CLU knockdown is associated with decreases in cellular VWF content but does not affect VWF mRNA levels or WPB quantity or size.

Unravelling the effect of blood group on FVIII:C levels and response to DDAVP in 20 males with a single genotype (Twillingate Variant) causing Haemophilia A

INTRODUCTION

The genetic variant responsible for haemophilia A (HA) significantly impacts endogenous coagulant factor VIII (FVIII:C) level, thus impacting DDAVP responsiveness. Blood group (BG) also impacts FVIII:C levels, but this is difficult to evaluate in a genetically heterogeneous population. Canada has a large cohort of mild-moderate HA due to a single point variant: c.6104T>C, p.Val2035Ala-the Twillingate variant.

AIM

To evaluate the impact of BG on endogenous FVIII:C levels and DDAVP responsiveness in a single genotype of mild-moderate HA.

METHODS

This was a retrospective, single-centre study. BG and FVIII:C levels were obtained for males with the Twillingate variant. One-hour absolute and fold increases in FVIII:C post-DDAVP were calculated. T-tests and Mann-Whitney U tests were used to compare FVIII:C levels and DDAVP challenge variables between individuals according to BGs (O vs. non-O).

RESULTS

Twenty males were included. There were significant differences between BGs (O vs. non-O) in their lowest FVIII:C level at age <12 years (medians: 0.05 vs. 0.08 IU/mL; P = .05). Fifteen subjects underwent DDAVP challenges. Mean 1-h FVIII:C were 0.29 (O BG) versus 0.41 IU/mL (non-O BG); P = .04. There were no significant differences between BGs (O vs. non-O) in mean absolute FVIII:C increase (0.20 vs. 0.27 IU/mL; P = .10) and FVIII:C fold increase (3.3-fold vs. 3.8-fold; P = .51).

CONCLUSION

In HA subjects with an identical genotype, BG significantly impacts baseline FVIII:C levels and FVIII:C levels post-DDAVP, but does not impact absolute and fold increases in FVIII:C with DDAVP.

The necessity of repeat testing for von Willebrand disease in adult patients with mild to moderate bleeding disorders

BACKGROUND

In patients with mild-to-moderate bleeding disorders (MBD), von Willebrand disease (VWD) is diagnosed at von Willebrand factor (VWF) levels ≤50 IU/dL. Although VWF levels are unstable, repeated testing for VWD diagnosis is not necessarily advised in recent guidelines.

OBJECTIVES

To analyze the relevance of repeated VWF testing to diagnose VWD in patients with MBD.

METHODS

Data of 277 patients with MBD from the Vienna Bleeding Biobank with at least 2 separate assessments of VWF antigen (VWF:Ag) and activity (VWF:Act) were analyzed.

RESULTS

In repeated VWF measurements, 36 patients (13.0%) had "changing" VWF levels (≤/>50 IU/dL), 27 (9.7%) had persistent levels ≤50 IU/dL ("pathologic"), and 214 (77.3%) had levels >50 IU/dL ("normal"). Of the 36 changing patients, 22 (61%) were diagnosed with VWD at baseline, whereas the others only met VWD diagnostic criteria at repeated measurements. Using logistic regression, we estimated a probability of change of 26.4% (95% CI, 12.5-47.4) at baseline VWF levels of 30 IU/dL, 50.8% (95% CI, 35.6-65.8) at 50 IU/dL, 18.8% (95% CI, 12.3-27.6) at 60 IU/dL, and 1.2% (95% CI, 0.3-4.9) at 80 IU/dL. Baseline VWF was a strong predictor for changing status (Χ2 = 49.9; P < .001), while age, sex, Vicenza score, and blood type O had limited added value (Χ2 = 5.1; P = .278). Baseline VWF:Ag or VWF:Act cutoffs of 80 IU/dL had negative predictive values of 98.1% and 99.1% for changing status, respectively.

CONCLUSION

Our data emphasize an overlap between patients with VWD and MBD with bleeding disorder of unknown cause and underline the need for repeated VWF testing, especially in patients with VWF levels <80 IU/dL.

In vitro field study and worldwide survey assessing how clinical haemostasis laboratories analyse recombinant and plasma-derived von Willebrand factor products

INTRODUCTION

Several well-established clinical laboratory methods are available to measure von Willebrand factor (VWF) in plasma samples, but few data are available on their use for analysing recombinant VWF (rVWF).

AIM

To evaluate how clinical diagnostic laboratories analyse rVWF and plasma-derived VWF (pdVWF) spiked in vitro into VWF-deficient plasma using quantitative protein and functional assays of VWF.

METHODS

Human VWF-deficient plasma samples were spiked with rVWF (vonicog alfa; Takeda) or pdVWF/factor VIII (pdVWF/FVIII; antihemophilic factor/VWF complex [human], CSL Behring), each at final concentrations of 1.0, 0.6, 0.2, 0.1 IU/mL VWF:ristocetin cofactor activity (VWF:RCo) according to labelled VWF activity. The ISTH SSC secondary coagulation standard was used as a control. Participating laboratories received three sets of these blinded aliquots. Mean results per assay were compared with the expected potency based on the labelled VWF:RCo activity.

RESULTS

Among 39 laboratories, the most commonly established assay was VWF:RCo; 22 laboratories reported data from 2214 tests. Despite a trend to lower values, VWF:RCo activities for rVWF were in agreement with target concentrations (71%-109%), whereas VWF:platelet glycoprotein Ib (VWF:GpIb) and VWF collagen-binding activity (VWF:CB) assays gave high recoveries (up to 132% and 127%, respectively). In contrast, pdVWF/FVIII was substantially underestimated by VWF:GpIb and VWF:CB assays (56%-86% recoveries), whereas the VWF:RCo assay gave recoveries of 47%-112% for pdVWF/FVIII.

CONCLUSION

The results of VWF assays used in clinical laboratories differ between rVWF and pdVWF, particularly for VWF:GpIb and VWF:CB assays. These differences may arise from the higher multimeric structure of rVWF compared to pdVWF.

Epidemiological study of hereditary hemorrhagic disorders in Najaf province, Iraq

Hemophilia and Von Willbrand disease (VWD) are the most well known types of hereditary hemorrhagic disorders (HHD). Hemophilia affects about 200 000 people worldwide, while VWD affects about 80 000. Because there is a scarcity of epidemiologic studies on hemophilia in Iraq, this study was carried out to evaluate the prevalence and incidence trends, as well as to identify some clinical and epidemiological features of hemophilia patients in Najaf province, Iraq. This study was carried out in the Najaf's hemophilia center. The data were obtained by reviewing all patients' documents, as well as the center registration book from 2011 to 2021. In addition, the Ministry of Health provided relevant population data for Najaf. Notably, there are currently 214 patients registered in Najaf province. The results revealed that the severe form of hemophilia A was the permanent type of HHDs in the patients compared with the rest of the types that include HHD with no significant difference Pat least 0.05. The frequency of this group of disorders appeared to increase in the period between 2011 and 2013, especially in 2012 followed by a decline in the incidence until 2021, which recorded a sudden increase in these disorders. These findings highlight that hemophilia types A and B were the most prevalent disorders of HHD in Najaf province, and the increase in number of newly recorded cases because of consanguineous marriage increased recently in this area.

Dynamic and functional linkage between von Willebrand factor and ADAMTS-13 with aging: an Atherosclerosis Risk in Community study

BACKGROUND

von Willebrand factor (VWF) is a multimeric glycoprotein critically involved in hemostasis, thrombosis, and inflammation. VWF function is regulated by its antigen levels, multimeric structures, and the state of enzymatic cleavage. Population studies in the past have focused almost exclusively on VWF antigen levels in cross-sectional study designs.

OBJECTIVE

To identify subjects in the Atherosclerosis Risk in Community study who had persistently low and high VWF antigen over 10 years and to quantify longitudinal changes in the biological activities and cleavage of VWF in these subjects.

METHODS

We measured VWF antigen, propeptide, adhesive activities, and cleavage by ADAMTS-13 quantified using a mass spectrometry method that detected the cleaved VWF peptide EQAPNLVY, as well as coagulation factor VIII activity.

RESULTS

We determined the mean subject-specific increase in VWF to be 22.0 International Units (IU)/dL over 10 years, with 95% between -0.3 and 59.7 IU/dL. This aging-related increase was also detected in VWF propeptide levels, ristocetin cofactor activity, and VWF binding to collagen. We identified 4.1% and 25.0% of subjects as having persistently low (<50 IU/dL) and high (>200 IU/dL) VWF antigen, respectively. Subjects with persistently low VWF had enhanced ristocetin cofactor activity, whereas those with persistently high VWF had elevated levels of ADAMTS-13, resulting in a comparable rate of VWF cleavage between the 2 groups.

CONCLUSIONS

These results provide new information about the effects of aging on VWF antigens and adhesive activity and identify a functional coordination between VWF and the rate of its cleavage by ADAMTS-13.

Aging Is Associated With Organ-Specific Alterations in the Level and Expression Pattern of von Willebrand Factor

BACKGROUND

VWF (von Willebrand factor) is an endothelial-specific procoagulant protein with a major role in thrombosis. Aging is associated with increased circulating levels of VWF, which presents a risk factor for thrombus formation.

METHODS

Circulating plasma, cellular protein, and mRNA levels of VWF were determined and compared in young and aged mice. Major organs were subjected to immunofluorescence analyses to determine the vascular pattern of VWF expression and the presence of platelet aggregates. An in vitro model of aging, using extended culture time of endothelial cells, was used to explore the mechanism of age-associated increased VWF levels.

RESULTS

Increased circulating plasma levels of VWF with elevated levels of larger multimers, indicative of VWF functional activity, were observed in aged mice. VWF mRNA and cellular protein levels were significantly increased in the brains, lungs, and livers but not in the kidneys and hearts of aged mice. Higher proportion of small vessels in brains, lungs, and livers of aged mice exhibited VWF expression compared with young, and this was concomitant with increased platelet aggregate formation. Prolonged culture of endothelial cells resulted in increased cell senescence that correlated with increased VWF expression; VWF expression was specifically detected in senescent cultured endothelial cells and abolished in response to p53 knockdown. A significantly higher proportion of VWF expressing endothelial cells in vivo exhibited senescence markers SA-β-Gal (senescence-associated β-galactosidase) and p53 in aged mouse brains compared with that of the young.

CONCLUSIONS

Aging elicits a heterogenic response in endothelial cells with regard to VWF expression, leading to organ-specific increase in VWF levels and alterations in vascular tree pattern of expression. This is concomitant with increased platelet aggregate formation. The age-associated increase in VWF expression may be modulated through the process of cell senescence, and p53 transcription factor contributes to its regulation.

A novel von Willebrand factor multimer ratio as marker of disease activity in thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP), an autoantibody-mediated severe ADAMTS13 deficiency, is caused by insufficient proteolytic processing of von Willebrand factor (VWF) multimers (MMs) and microvascular thrombi. Recurrence of acute iTTP is associated with persistence or reappearance of ADAMTS13 deficiency. Some patients remain in remission despite recurring or persisting severe ADAMTS13 deficiency. In a prospective 2-year observational study, we investigated VWF MM patterns and ADAMTS13 in patients with iTTP in remission and at acute episodes. Of the 83 patients with iTTP, 16 suffered 22 acute episodes whereas 67 remained in clinical remission during follow-up, including 13 with ADAMTS13 <10% and 54 with ADAMTS13 ≥10%. High -molecular weight to low-molecular weight VWF MM ratio based on sodium dodecyl sulfate-agarose gel electrophoresis was compared with ADAMTS13 activity. VWF MM ratio was significantly higher in patients in remission with <10% compared with ≥10% ADAMTS13 activity. Fourteen samples obtained from 13 to 50 days (interquartile range; median, 39) before acute iTTP onset (ADAMTS13 <10% in 9 patients and 10%-26% in 5) showed VWF MM ratios significantly higher than those from 13 patients remaining in remission with ADAMTS13 <10%. At acute iTTP onset, VWF MM ratio decreased significantly and was low in all patients despite <10% ADAMTS13. The VWF MM ratio does not depend exclusively on ADAMTS13 activity. The disappearance of high molecular weight VWF MMs resulting in low VWF MM ratio at iTTP onset may be explained by consumption of larger VWF MMs in the microcirculation. The very high VWF MM ratio preceding acute iTTP recurrence suggests that VWF processing is hampered more than in patients remaining in remission.

Integrated Approach to Highlighting the Molecular Bases of a Deep Vein Thrombosis Event in an Elite Basketball Athlete

Acute or intense exercise can result in metabolic imbalances, muscle injuries, or reveal hidden disorders. Laboratory medicine in sports is playing an increasingly crucial role in monitoring athletes' health conditions. In this study, we designed an integrated approach to explore the causes of a deep venous thrombosis event in an elite basketball player. Since the complete blood count revealed a marked platelet count (838 × 103 µL), and thrombophilia screening tests did not reveal any significant alteration, we evaluated the thrombin generation, which highlights a state of hypercoagulability. First-level haemostasis exams showed only a slight prolongation of the activated Partial Thromboplastin Time (aPTT). Thus, screening tests for von Willebrand Disease showed a reduction in vWF parameters. Therefore, we directed our hypothesis towards a diagnosis of acquired von Willebrand disease secondary to Essential Thrombocythemia (ET). To confirm this hypothesis and highlight the molecular mechanism underlying the observed phenotype, molecular tests were performed to evaluate the presence of the most common mutations associated with ET, revealing a 52-bp deletion in the coding region of CALR exon 9. This case report highlights the importance of an integrated approach to monitoring the athletes' health status to personalise training and treatments, thus avoiding the appearance of diseases and injuries that, if underestimated, can undermine the athlete's life.

National strategic advocacy to manage patients with inherited bleeding disorders in low and lower-middle income countries

INTRODUCTION

Inherited bleeding disorders (IBDs) including hemophilia, von Willebrand disease, platelet disorders, mucocutaneous bleeding disorders and coagulation factor deficiencies are rarely found and under-recognized in low and lower-middle-income countries. Some patients succumbed to serious bleeding without diagnosis and treatment during childhood.

AREA COVERED

Diagnosis, management, and prevention should be integrated into the existing health care system. Although some countries have not implemented appropriate health care infrastructure, an initiative plan should be set up by cooperation of experienced experts and health care providers. Identification of patients with IBDs should be started in the antenatal setting to search for females at risk of carrier state. The investigations include bleeding assessment, mixing venous clotting time, coagulogram, coagulation factor assay and mutation detection. Genotypic analysis is helpful for confirming the definite diagnosis, carrier detection as well as prenatal diagnosis for females at risk of bearing an offspring with severe bleeding manifestations. Management involves replacement therapy ranging from blood component to virus-inactivated factor concentrate. Appropriate research is an essential backbone for improving patients' care.

EXPERT OPINION

Effective national strategic advocacy to manage patients with IBDs requires intensive collaboration among policy makers, health care providers, patients, and family members.

Kinetic and Dynamic Effects on Degradation of von Willebrand Factor

The loss of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in aortic stenosis (AS) and continuous-flow left ventricular assist devices (cf-LVADs) is believed to be associated with high turbulent blood shear. The objective of this study is to understand the degradation mechanism of HMWM in terms of exposure time (kinetic) and flow regime (dynamics) within clinically relevant pathophysiologic conditions. A custom high-shear rotary device capable of creating fully controlled exposure times and flows was used. The system was set so that human platelet-poor plasma flowed through at 1.75 ml/sec, 0.76 ml/sec, or 0.38 ml/sec resulting in the exposure time ( texp ) of 22, 50, or 100 ms, respectively. The flow was characterized by the Reynolds number (Re). The device was run under laminar (Re = 1,500), transitional (Re = 3,000; Re = 3,500), and turbulent (Re = 4,500) conditions at a given texp followed by multimer analysis. No degradation was observed at laminar flow at all given texp . Degradation of HMWM at a given texp increases with the Re. Re ( p < 0.0001) and texp ( p = 0.0034) are significant factors in the degradation of HMWM. Interaction between Re and texp , however, is not always significant ( p = 0.73).

Prolonged Elevations of Factor VIII and von Willebrand Factor Antigen After Multisystem Inflammatory Syndrome in Children

Multisystem Inflammatory Syndrome in Children (MIS-C) is a late systemic inflammatory response to a recent mild or asymptomatic coronavirus disease of 2019 infection. The pathophysiology is incompletely understood but it often features significant coagulopathy along with cardiac and endothelial dysfunction. Endothelial inflammation has been primarily described in acute coronavirus disease of 2019 infection, with less characterization in MIS-C. Here we describe novel findings of nearly universal severe and prolonged factor VIII (FVIII) and von Willebrand factor antigen elevations in an institutional cohort of patients with MIS-C ages younger than or 21 years old (N=31). All patients had elevated acute phase reactants and D-dimer at presentation and met published criteria for MIS-C. FVIII was high at presentation in 97% of patients but continued to rise during the ensuing weeks of treatment to a mean 429%, peaking on median day 17 of illness as an outpatient. FVIII levels were >600% in multiple patients. von Willebrand factor antigen was measured less frequently but showed similar trends. These escalations occurred amidst resolving cardiac dysfunction and acute phase reactant normalization and despite patients receiving multimodal anti-inflammatory treatments and aspirin and enoxaparin thromboprophylaxis. No thrombotic events occurred. Endothelial dysfunction represented by very elevated FVIII levels may persist longer than other acute phase reactants may reflect.

Loss of pulsatility with continuous-flow left ventricular assist devices and the significance of the arterial endothelium in von-Willebrand factor production and degradation

BACKGROUND

Patients on continuous flow ventricular assist devices (CF-VADs) are at high risk for the development of Acquired von-Willebrand Syndrome (AVWS) and non-surgical bleeding. von Willebrand Factor (vWF) plays an essential role in maintaining hemostasis via platelet binding to the damaged endothelium to facilitate coagulation. In CF-VAD patients, degradation of vWF into low MW multimers that are inefficient in facilitating coagulation occurs and has been primarily attributed to the supraphysiological shear stress associated with the CF-VAD impeller.

METHODS

In this review, we evaluate information from the literature regarding the unraveling behavior of surface-immobilized vWF under pulsatile and continuous flow pertaining to: (A) the process of arterial endothelial vWF production and release into circulation, (B) the critical shear stress required to unravel surface bound versus soluble vWF which leads to degradation, and (C) the role of pulsatility in on the production and degradation of vWF.

RESULTS AND CONCLUSION

Taken together, these data suggests that the loss of pulsatility and its impact on arterial endothelial cells plays an important role in the production, release, unraveling, and proteolytic degradation of vWF into low MW multimers, contributing to the development of AVWS. Restoration of pulsatility can potentially mitigate this issue by preventing AVWS and minimizing the risk of non-surgical bleeding.

Changes in von Willebrand Factor Multimers, Concentration, and Function During Pediatric Extracorporeal Membrane Oxygenation

OBJECTIVES

To investigate changes in von Willebrand factor (VWF) concentration, function, and multimers during pediatric extracorporeal membrane oxygenation (ECMO) and determine whether routine monitoring of VWF during ECMO would be useful in predicting bleeding.

DESIGN

Prospective observational study of pediatric ECMO patients from April 2017 to May 2019.

SETTING

The PICU in a large, tertiary referral pediatric ECMO center.

PATIENTS

Twenty-five neonates and children (< 18 yr) supported by venoarterial ECMO.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arterial blood samples were collected within 24 hours pre-ECMO, daily for the first 5 days of ECMO, every second day until decannulation, and 24 hours post-ECMO. The STA R Max analyzer was used to measure VWF antigen (VWF:Ag) and ristocetin cofactor (VWF:RCo) activity. VWF collagen binding (VWF:CB) was measured using an enzyme-linked immunosorbent assay. VWF multimers were measured using the semi-automated Hydragel 11 VWF Multimer assay. Corresponding clinical data for each patient was also recorded. A total of 25 venoarterial ECMO patients were recruited (median age, 73 d; interquartile range [IQR], 3 d to 1 yr). The median ECMO duration was 4 days (IQR, 3-8 d) and 15 patients had at least one major bleed during ECMO. The percentage of high molecular weight multimers (HMWM) decreased and intermediate molecular weight multimers increased while patients were on ECMO, irrespective of a bleeding status. VWF:Ag increased and the VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios decreased while patients were on ECMO compared with the baseline pre-ECMO samples and healthy children.

CONCLUSIONS

Neonates and children on ECMO exhibited a loss of HMWM and lower VWF:CB/VWF:Ag and VWF:RCo/VWF:Ag ratios compared with healthy children, irrespective of major bleeding occurring. Therefore, monitoring VWF during ECMO would not be useful in predicting bleeding in these patients and changes to other hemostatic factors should be investigated to further understand bleeding during ECMO.

Enhanced VWF clearance in low VWF pathogenesis: limitations of the VWFpp/VWF:Ag ratio and clinical significance

Increased von Willebrand factor (VWF) clearance plays a key role in the pathogenesis of type 1 and type 2 von Willebrand disease (VWD). However, the pathological mechanisms involved in patients with mild to moderate reductions in plasma VWF:Ag (range, 30-50 IU/dL; low VWF) remain poorly understood. In this study, we investigated the hypothesis that enhanced VWF clearance may contribute to the pathobiology of low VWF. Patients with low VWF were recruited to the LoVIC study after ethics approval and receipt of informed consent. Desmopressin was administered IV in 75 patients, and blood samples were drawn at baseline and at the 1-hour and 4-hour time points. As defined by recent ASH/ISTH/NHF/WFH guidelines, 20% of our low-VWF cohort demonstrated significantly enhanced VWF clearance. Importantly, from a clinical perspective, this enhanced VWF clearance was seen after desmopressin infusion, but did not affect the steady-state VWF propeptide (VWFpp)-to-VWF antigen (VWF:Ag) ratio (VWFpp/VWF:Ag) in most cases. The discrepancy between the VWFpp/VWF:Ag ratio and desmopressin fall-off rates in patients with mild quantitative VWD may have reflected alteration in VWFpp clearance kinetics. Finally, bleeding scores were significantly lower in patients with low VWF with enhanced VWF clearance, compared with those in whom reduced VWF biosynthesis represented the principle pathogenic mechanism. This trial was registered at http://www.clinicaltrials.gov as #NCT03167320.

Heterogeneity in the half-life of factor VIII concentrate in patients with hemophilia A is due to variability in the clearance of endogenous von Willebrand factor

BACKGROUND

Previous studies have reported marked interindividual variation in factor VIII (FVIII) clearance in patients with hemophilia (PWH) and proposed a number of factors that influence this heterogeneity.

OBJECTIVES

To investigate the importance of the clearance rates of endogenous von Willebrand factor (VWF) compared with those of other FVIII half-life modifiers in adult PWH.

METHODS

The half-life of recombinant FVIII was determined in a cohort of 61 adult PWH. A range of reported modifiers of FVIII clearance was assessed (including plasma VWF:antigen and VWF propeptide levels; VWF-FVIII binding capacity; ABO blood group; and nonneutralizing anti-FVIII antibodies). The FVIII-binding region of the VWF gene was sequenced. Finally, the effects of variation in FVIII half-life on clinical phenotype were investigated.

RESULTS

We demonstrated that heterogeneity in the clearance of endogenous plasma VWF is a key determinant of variable FVIII half-life in PWH. Both ABO blood group and age significantly impact FVIII clearance. The effect of ABO blood group on FVIII half-life in PWH is modulated entirely through its effect on the clearance rates of endogenous VWF. In contrast, the age-related effect on FVIII clearance is, at least in part, VWF independent. In contrast to previous studies, no major effects of variation in VWF-FVIII binding affinity on FVIII clearance were observed. Although high-titer immunoglobulin G antibodies (≥1:80) were observed in 26% of PWH, these did not impact FVIII half-life. Importantly, the annual FVIII usage (IU/kg/y) was significantly (p = .0035) increased in patients with an FVIII half-life of <12 hours.

CONCLUSION

Our data demonstrate that heterogeneity in the half-life of FVIII concentrates in patients with hemophilia A is primarily attributable to variability in the clearance of endogenous VWF.

Severe bleeding diathesis as onset of light-chain amyloidosis: combined excessive fibrinolysis and acquired von Willebrand disease in a young patient

Our report shows a case of primary light-chain amyloidosis in a young patient that reflects the potential severity of bleeding diathesis associated with this plasma cell dyscrasia and the difficulty of diagnosis when only hemorrhagic manifestations are present at the onset of disease. The patient presented with recurrent and severe muscular bleeding secondary to associated acquired von Willebrand disease and fibrinolysis dysfunction. Treatment with bortezomib-cyclophosphamide and sequential hematopoietic stem cell transplantation solved coagulation alterations. On the basis of our case, we review previous reports and discuss the potential mechanism of dysfunction of coagulation in light-chain amyloidosis.

Thrombin formation via the intrinsic coagulation pathway and von Willebrand factor reflect disease severity in COVID-19

Not available.

ADAMTS13 inhibition to treat acquired von Willebrand syndrome during mechanical circulatory support device implantation

BACKGROUND

Acquired von Willebrand syndrome (aVWS) is common in patients with mechanical circulatory support (MCS) devices. In these patients, the high shear stress in the device leads to increased shear-induced proteolysis of von Willebrand factor (VWF) by A Disintegrin And Metalloprotease with Thrombospondin type 1 repeats, number 13 (ADAMTS13). As a result, the high molecular weight (HMW) VWF multimers are lost, leading to a decreased VWF function and impaired hemostasis that could explain the bleeding complications that are frequently observed in these patients. To counteract this abnormal VWF degradation by ADAMTS13, we developed a novel targeted therapy, using an anti-ADAMTS13 monoclonal antibody (mAb) that inhibits the shear-induced proteolysis of VWF by ADAMTS13.

METHODS

Human or bovine blood was circulated through in vitro MCS device systems with either inhibitory anti-ADAMTS13 mAb 3H9 or 17C7 (20 μg/ml) or control anti-ADAMTS13 mAb 5C11 or phosphate buffered saline (PBS). VWF multimers and function (collagen binding activity) were determined at different time points. Next, Impella pumps were implanted in calves and the calves were injected with PBS and subsequently treated with mAb 17C7. VWF, ADAMTS13, and blood parameters were determined.

RESULTS

We demonstrated that blocking ADAMTS13 could prevent the loss of HMW VWF multimers in in vitro MCS device systems. Importantly, our antibody could reverse aVWS in a preclinical Impella-induced aVWS calf model.

CONCLUSION

Hence, inhibition of ADAMTS13 could become a novel therapeutic strategy to manage aVWS in MCS device patients.

[The Effect of VWF Propeptide on VWF Mutant in D1 Domain]

OBJECTIVE

To investigate whether co-transfection of wild-type VWFpp with VWF mutant in D1 region is able to correct VWF defects in biosynthesis and secretion.

METHODS

Four VWF mutant plasmids were single transfected into HEK 293 cells, or co-transfected into HEK 293 cells with the wild type VWFpp plasmids. The VWF in supernatant and lysate of transfected cells were analyzed by ELISA, vertical VWF multimer electrophoresis. The retention of VWF in endoplasmic reticulum of transfected cells were detected by immunofluorescence confocal microscope.

RESULTS

In the vertical VWF multimer analysis, with co-expressing VWF mutant and VWFpp, the VWF multimer bands disappeared, and the VWF antigen in both supernatant and lysate of cells decreased, compared with the single expression of VWF mutant. Although the intracellular levels of VWF antigens decreased after co-expression, the retention rate of VWF mutant decreased in endoplasmic reticulum.

CONCLUSION

VWFpp can reduce the retention of VWF in endoplasmic reticulum, assists the transport of VWF between subcellular organelles. However, VWFpp inhibits the biosynthesis and secretion of VWF about the mutant in D1 domain.

The p.P1127S pathogenic variant lowers von Willebrand factor levels through higher affinity for the macrophagic scavenger receptor LRP1: Clinical phenotype and pathogenic mechanisms

BACKGROUND

The index case is a 21-year-old Italian woman with a mild hemorrhagic syndrome and von Willebrand factor antigen (VWF:Ag) = 34.3 U/dl, VWF recombinant glycoprotein Ib (VWF:GpIbR) = 32.8 U/dl, and factor VIII (FVIII) = 55.3 IU/dl.

AIMS

The aim of this study is to characterize from a genetic and biochemical standpoint this low VWF phenotype.

METHODS

Coagulation and biochemical methods were used to study the structural and functional pattern of VWF multimers in the index case's plasma. Recombinant wild-type and p.P1127S VWF variants were produced using human embryonic kidney (HEK)-293 cells. In addition, genetic screening was carried out to detect single nucleotide variants of some scavenger VWF/FVIII receptor genes such as CLEC4M, STAB2, and ASGR2.

RESULTS

Genetic investigation revealed that the index case inherited from her mother the heterozygous missense mutation c.3379C > T (VWF exon 25), causing the p.P1127S substitution in the VWF D'D3 domain. The index case was also homozygous for the scavenger receptor ASGR2 c.-95 CC-genotype. Desmopressin normalized the VWF level of the patient, although its clearance was faster (t1/2  = 6.7 h) than in normal subjects (t1/2  = 12 ± 0.7 h). FVIII-VWF interaction, A Disintegrin And Metalloprotease with ThromboSpondin type 1 motif-13 levels, ristocetin-induced-platelet-aggregation, and VWF multimeric pattern were normal. The p.P1127S variant was normally synthesized and secreted by HEK-293 cells, and molecular modeling predicts a conformational change showing higher affinity for the macrophagic scavenger receptor lipoprotein receptor-related protein 1 (LRP1), as also experimentally verified.

CONCLUSIONS

The p.P1127S variant may cause a low VWF phenotype, stemming from an increased VWF affinity for the scavenger receptor LRP1 and, consequently, an accelerated clearance of VWF.

Acquired Factor V Deficiency: A New Cause of Bleeding in Patients with Chronic Myeloid Leukemia and Extreme Leukocytosis

Bleeding complications in patients with myeloproliferative neoplasms are known to be related to acquired von Willebrand disease or platelet dysfunction. Here, we describe two very similar cases of chronic phase chronic myeloid leukemia with extreme leukocytosis (>500,000/mcL) and deep tissue bleeding after a minor trauma, who had increased PT and PTT, normal VWF antigen and activity. The patients were found to have acquired factor V deficiency. Factor V deficiency as a cause of bleeding in patients with uncontrolled chronic myeloid leukemia has not yet been reported. Bleeding resolved after correction of hyperleukocytosis, and FV level improved. We conclude that acquired FV deficiency is possible in patients with uncontrolled chronic myeloid leukemia and extreme leukocytosis.

Von Willebrand Factor Multimer Patterns in People Living with Human Immunodeficiency Virus Infection

BACKGROUND

Endothelial dysfunction contributes to hypercoagulability in people with HIV (PWH). A surrogate marker of this is elevated von Willebrand factor (VWF) which has been documented in PWH. This study compared VWF multimer patterns in PWH who were anti-retroviral therapy (ART) naive and immune reconstituted on ART.

METHODS

VWF multimer analysis was performed with a semi-quantitative electrophoresis assay on plasma from 79 PWH (39 ART-naive and 40 virally suppressed on ART) and 25 normal control samples.

RESULTS

The total optical density mean VWF level was significantly increased in PWH and higher in ART-naive versus ART-exposed, virally suppressed patients (p < 0.0001). No quantitative difference was demonstrated in the multimer distribution pattern between the groups.

CONCLUSIONS

Our findings suggest that there is no difference in multimer distribution between ART-naive and virally suppressed PWH. Due to a small sample size, confirmation in a larger study is required.

Tissue dynamics of von Willebrand factor characterized by a novel fluorescent protein-von Willebrand factor chimera

BACKGROUND

Tissue dynamics of von Willebrand factor (VWF) that are vital to its biological function have not been fully characterized.

OBJECTIVE

To develop a new fluorescent protein--VWF chimera (FP-VWF) that has similar hematologic function to wild-type VWF and use it to monitor the tissue dynamics of VWF distribution.

METHODS

Genotyping, platelet counting, tail bleeding time assay, agarose gels, western blot, platelet aggregation, proteolytic analysis, and ELISA were applied in characterizing the function of FP-VWF; fluorescence spectrometer and confocal fluorescence microscope were used to monitor the plasma and tissue distribution of FP-VWF.

RESULTS

The transgenic mice that carry the FP-VWF retain hematologic activity of VWF with plasma levels of FP-VWF reduced by 50% and there are reduced high molecular weight FP-VWF multimers compared to the wild-type mice. The GPIb-binding and ADAMTS-13 (A Disintegrin and Metalloprotease with ThrombSpondin type 1 motif, member 13) proteolytic efficiency of FP-VWF are similar to wild-type VWF. The tissue distribution of FP-VWF was probed directly through its intrinsic fluorescence at normal or stimulated status, which indicated that the medicine-stimulated endogenous FP-VWF seems primarily released from the aorta and cleared in the spleen. Similar results were observed in non-fluorescent mice through a standard immunofluorescence approach. The fluorescence signals of FP-VWF were also similar to the standard dye-based approach in detecting the FeCl3 -induced blood clotting in vivo.

CONCLUSIONS

Together, these results suggest that this novel FP-VWF chimera is valuable in probing the tissue dynamics of VWF in quite a few biological and pharmaceutical applications.

Usefulness of Routine Coagulation Tests in Healthy Children Undergoing Elective Minor Surgery: a 12-Year Retrospective Study

BACKGROUND

Although routine coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT) are performed before surgery to identify the risk of perioperative bleeding, bleeding complications are rare in minor surgeries, and false-positive results are often observed. Therefore, this study aimed to analyze the common causes of abnormal results of preoperative coagulation tests in previously healthy children undergoing elective minor surgery and determine the usefulness of performing these tests. Additionally, it aimed to identify the distribution of factor XII activity in children with prolonged aPTT.

METHODS

The medical records of 363 pediatric patients aged 0 - 18 years, who were referred to the pediatric hematology-oncology department due to abnormal preoperative coagulation tests prior to undergoing minor surgery at the Kyung Hee University Medical Center between March 2008 and October 2020, were retrospectively review-ed.

RESULTS

The majority of patients (n = 348, 96%) had prolonged aPTT, few (n = 29, 8%) had a prolonged PT international normalized ratio, and a small number (n = 14, 4%) had both prolonged PT and aPTT. On repeating the coagulation tests, 194 children showed persistent abnormal results. Of these, 184 patients underwent mixing tests, and 176 showed correction for factor deficiency (n = 26) and lupus anticoagulant positive (n = 14). Factor deficiencies included factor XII (n = 16), possibility of von Willebrand disease (vWD; n = 4), factor XI (n = 2), factor VIII (n = 1), factors IX and XII (n = 1), factor VII (n = 1), and factor V (n = 1). The severity of factor deficiency was mild (25 - 38%). One patient with factor VII deficiency received preoperative clotting factors but had postoperative bleeding requiring clotting factor replacement. Another patient with possible vWD received fresh frozen plasma after surgery and had mild symptoms. Linear regression showed no significant correlation between factor XII activity and aPTT in patients with prolonged aPTT (R2 = 0.0002, p = 0.84) or factor XII activity according to aPTT results in those with factor XII deficiency (R2 = 0.04749, p = 0.40).

CONCLUSIONS

These results suggest that coagulation tests may be selectively performed in previously healthy children undergoing minor surgery with positive bleeding and/or family history. The distribution of factor XII should be investigated further.

Do we need to evaluate patients with spontaneous subconjunctival haemorrhage for bleeding disorders?

AIM OF THE STUDY

Subconjunctival haemorrage (SCH) is a frequent bleeding manifestation and a common cause of visits to the primary care. Trauma in young patients and vascular damage such as hypertension in the elderly are the most common causes of SCH and the prevalence of haematological diseases is <1%. We aimed to evaluate the prevalence of congenital or acquired bleeding disorders in patients with once or recurrent SCH.

METHODS USED TO CONDUCT THE STUDY

It is a retrospective study and included fifty-two patients with SCH whose aetiologic factor was not detected. Haemostatic tests were studied in 52 patients (25 male and 27 females). All patients included were evaluated for congenital or acquired bleeding disorder and SCH with once and those with two or more were compared for the laboratory results.

RESULTS OF THE STUDY

Type I von Willebrand disease (vWD) was diagnosed in one patient with recurrent SCH and one patient with single SCH (3.8%). The prevalence of patients with type 1 vWD in the study was not statistically significant when compared with the frequency of vWD in the normal population. Fibrinogen level was found to be statistically higher in patients who had SCH once than those who had recurrent SCH. However, fibrinogen level was in normal range in all patients.

CONCLUSIONS DRAWN FROM THE STUDY AND CLINICAL IMPLICATIONS

There was no increase in the incidence of congenital or acquired bleeding disorder in SCH compared with normal population. Fort this reason, it was thought there was no need for evaluation for bleeding disorders in spontaneous SCH.

Bernard Soulier syndrome: a rare, frequently misdiagnosed and poorly managed bleeding disorder

Bernard Soulier syndrome is a rare, congenital platelet bleeding disorder, with autosomal recessive inheritance. It is characterised by macrothrombocytopenia and platelet dysfunction, leading to mucocutaneous bleeding noted in early childhood. This entity poses an important diagnostic challenge, and blood smear and DNA sequencing are paramount for the correct diagnosis. Differential diagnosis includes May-Hegglin anomaly, Glanzmann Thrombasthenia and von Willebrand disease; it is also often misdiagnosed as idiopathic thrombocytopenic purpura. We report a 68-year-old man diagnosed with von Willebrand disease for three decades, admitted with gastrointestinal bleeding, anaemia and severe thrombocytopenia. Replacement with von Willebrand factor did not stop the haemorrhage, suggesting another aetiology for the bleeding disorder. Corticosteroids and intravenous immune globulin were also ineffective. Genetic sequencing showed a homozygous mutation in GP1BA gene, thus establishing the correct diagnosis.

Targeting von Willebrand factor in liver diseases: A novel therapeutic strategy?

Acute and chronic liver disease are associated with substantial alterations in the hemostatic system. Evidence from both experimental and clinical studies suggests that anticoagulants slow the progression of liver disease. Efficacy of those anticoagulant drugs is, in part, attributed to a reduction of microthrombi formation within the liver. Although anticoagulant drugs show promising results, bleeding risk associated with these drugs is an obvious drawback, particularly in patients with a complex coagulopathy driven by decreased liver function. Identifying therapies that reduce intrahepatic thrombosis with minimal bleeding risk would significantly advance the field. Among the hemostatic alterations observed in patients are substantially increased levels of the platelet-adhesive protein von Willebrand factor (VWF). In contrast, levels of A Disintegrin and Metalloproteinase with Thrombospondin motifs, the enzyme that regulates VWF activity, are significantly reduced in patients with liver disease. Highly elevated VWF levels are proposed to accelerate intrahepatic thrombus formation and thus be a driver of disease progression. Strong clinical evidence suggesting a link between liver disease and changes in VWF is now being matched by emerging mechanistic data showing a detrimental role for VWF in the progression of liver disease. This review focuses on clinical and experimental evidence supporting a connection between VWF function and the progression of acute and chronic liver diseases. Furthermore, with the recent anticipated approval of several novel therapies targeting VWF, we discuss potential strategies and benefits of targeting VWF as an innovative therapy for patients with liver disease.

Management of elective procedures in low von Willebrand factor patients in the LoVIC study

BACKGROUND

Most individuals with mild to moderate reductions in plasma von Willebrand factor (VWF) levels do not demonstrate increased bleeding. However, some patients with plasma VWF levels of 30-50 IU/dl do have a significant bleeding phenotype. Management of these "low VWF" patients, who may have significant bleeding scores >10, around times of elective procedures continues to pose a common clinical challenge because of a lack of evidence.

OBJECTIVE

To investigate the safety and efficacy of different periprocedural management options for adult patients with low VWF.

METHODS

Treatment and outcomes were retrospectively reviewed for 160 invasive procedures performed in 60 patients with well characterized low VWF enrolled in the previously described Low Von Willebrand factor Ireland Cohort study.

RESULTS

We demonstrate that 1-desamino-8-D-arginine vasopressin is efficacious in preventing bleeding for both minor or major elective procedures in adult low VWF patients, even in those with significant bleeding histories. In addition, tranexamic acid alone is effective for low VWF patients undergoing nondental minor procedures. Importantly, age-related increases in plasma VWF:antigen levels above 50 IU/dl were not necessarily associated with complete correction of bleeding phenotype. Procedure-related bleeding complications were increased in low VWF patients who did not receive any hemostatic cover before their procedure.

CONCLUSION

Elective procedures in adult patients with low VWF should be managed in liaison with a comprehensive care tertiary referral center so that personalized treatment plans may be implemented before all minor or major elective procedures.

Factor VIII pharmacokinetics associates with genetic modifiers of VWF and FVIII clearance in an adult hemophilia A population

BACKGROUND

Factor VIII (FVIII) pharmacokinetics (PK) in adult hemophilia A populations are highly variable and have been previously determined to be influenced by von Willebrand factor:antigen (VWF:Ag), ABO blood group, and age. However, additional genetic determinants of FVIII PK are largely unknown.

OBJECTIVES

The contribution of VWF clearance, VWF-FVIII-binding activity, and genetic variants in VWF clearance receptors to FVIII PK in adult patients were assessed.

METHODS

FVIII PK assessment was performed in 44 adult subjects (age 18-61 years) with moderate or severe hemophilia A. VWF:Ag, VWF propeptide (VWFpp), VWFpp/VWF:Ag, and VWF:FVIII binding activity were measured. The VWF modifying loci CLEC4M, SCARA5, STAB2, and ABO, and the D'D3 FVIII-binding region of the VWF gene were genotyped.

RESULTS

VWF:Ag, VWFpp, and VWF:FVIIIB positively correlated with FVIII half-life and negatively correlated with FVIII clearance. VWFpp/VWF:Ag negatively correlated with FVIII half-life and positively correlated with FVIII clearance. The correlation between VWFpp/VWF:Ag and FVIII half-life was stronger for type non-O patients than for type O patients, suggesting that slower VWF clearance increases FVIII half-life. Patients heterozygous for the CLEC4M rs868875 variant had increased FVIII clearance when compared with individuals homozygous for the reference allele. The CLEC4M variable number of tandem repeat (VNTR) alleles were also associated with the rate of FVIII clearance. When compared with the quartile of patients with the fastest FVIII clearance, the quartile of patients with the slowest FVIII clearance had a decreased frequency of the CLEC4M 5-VNTR.

CONCLUSIONS

VWF-FVIII binding activity and genetic determinants of VWF clearance are important contributors to FVIII pharmacokinetics in adult patients.

Laboratory variability in the diagnosis of type 2 VWD variants

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

Von Willebrand factor and cancer; metastasis and coagulopathies

Von Willebrand factor (VWF) is a multimeric procoagulant plasma glycoprotein that mediates platelet adhesion along the endothelium. In addition to its role maintaining normal hemostasis, more recently novel biological functions for VWF have been described, including inflammation, angiogenesis, and metastasis. Significantly increased plasma VWF levels have been reported across a variety of cancer patient cohorts. Given that VWF is established as a risk factor for venous thrombosis, this is of direct clinical importance. Moreover, elevated VWF has also been observed localized within the tumor microenvironment, correlating with advanced disease stage and poorer clinical outcome. Critically, evidence suggests that elevated VWF levels in cancer patients may not only contribute to cancer associated coagulopathies but may also mediate cancer progression and metastasis. Studies have shown that VWF can promote pro-inflammatory signaling, regulate angiogenesis and vascular permeability, which may facilitate tumor cell growth and extravasation across the vessel wall. Endothelial secreted VWF multimers contribute to the adhesion and transendothelial migration of tumor cells key for tumor dissemination. In support of this, VWF inhibition attenuated metastasis in vivo. Perhaps most intriguingly, specific tumor cells have been reported to acquire de novo VWF expression which increases tumor-platelet heteroaggregates and confers enhanced metastatic activity. Current knowledge on the roles of VWF in cancer and in particular its contribution to metastasis and cancer associated coagulopathies is summarized in this review.

The discriminatory power of bleeding assessment tools in adult patients with a mild to moderate bleeding tendency

BACKGROUND

Bleeding assessment tools (BATs) have been developed to quantify bleeding severity. Their ability to predict for the diagnosis of a bleeding disorder has not been thoroughly investigated.

OBJECTIVES

To evaluate the ability of the Vicenza BAT and the ISTH BAT to distinguish patients with an established bleeding disorder from those with bleeding of unknown cause (BUC).

PATIENTS/METHODS

Three-hundred fifty-nine patients (228 with BUC, 64%) from the Vienna Bleeding Biobank were assessed in this study.

RESULTS

The bleeding scores were similar in patients with an established diagnosis of a bleeding disorder compared to patients with BUC. Both BATs had a low sensitivity and specificity for the diagnosis of a bleeding disorder with areas under the receiver operating characteristic (ROC) curves of 0.53 (95% confidence interval 0.47-0.60) for the Vicenza BAT and 0.52 (0.46-0.59) for the ISTH BAT. In terms of specific diagnoses, both scores were most accurate in diagnosing von Willebrand disease (VWD, areas under the ROC curve; Vicenza BAT 0.67 (0.45-0.90); ISTH BAT 0.70 (0.50-0.90)). A separate evaluation of different bleeding symptoms in patients who had undergone surgery and tooth extraction revealed that postpartum bleeding and bleeding from small wounds was predictive for diagnosing a MBD in multivariable analysis.

CONCLUSIONS

The Vicenza- and the ISTH BAT have a low ability to distinguish patients with an established bleeding disorder from those with BUC.

The spectrum and severity of bleeding in adolescents with low von Willebrand factor-associated heavy menstrual bleeding

Low von Willebrand factor (VWF) in adults is associated with significant bleeding, most notably heavy menstrual bleeding (HMB) and postpartum hemorrhage, although this has not been characterized in adolescents. The objectives of this analysis of a multicenter single arm observational cohort study in adolescents with low VWF-associated HMB were to describe the bleeding phenotype, HMB severity, and related complications. Eligibility criteria included postmenarchal females <21 years of age with HMB (Pictorial Blood Assessment Chart [PBAC] score >100) and low VWF (2 values of VWF activity ≥30 and ≤50 IU/dL). Patients diagnosed with other bleeding disorders were ineligible. Clinical phenotype data, including PBAC and Bleeding Assessment Tool (BAT) scores, laboratory data, and HMB management/outcome details, were extracted. Patient demographics and clinical characteristics were summarized as medians with minimum/maximum values or frequencies with percentages. Groups were compared using a Wilcoxon rank-sum test or Fisher's exact test. A total of 113 patients met inclusion criteria, and 2 were excluded. Ninety four percent had a significant bleeding phenotype (BAT score >2), with predominantly mucocutaneous bleeding (32%-44%), postprocedural/surgical bleeding (15%), and severe HMB (BAT HMB domain score ≥2; 90%). Bleeding complications included iron deficiency (60%), anemia (21%), transfusion (12%), and hospitalization (10%). Desmopressin challenge response in subjects tested was good and sustained. Several (48%) required combined therapy for HMB (hormonal/hemostatic), and one third did not show improvement despite therapy. Our results suggest that adolescent females with low VWF have a significant bleeding phenotype and resultant complications warranting a focus on prompt diagnosis, appropriate therapy, and prevention of complications.

Vascular endothelial cells evade complement-mediated membrane injury via Weibel-Palade body mobilization

BACKGROUND

Defective complement inhibition can lead to the formation of membrane attack complexes (MAC; C5b-9) on the plasma membranes of vascular endothelial cells, resulting in injury that drives the progression of thrombotic microangiopathy (TMA), a key pathology in kidney disease.

OBJECTIVE/METHODS

We examined the response of human endothelial cells to complement-mediated damage using blood outgrowth endothelial cells (BOECs) derived from healthy donors. BOECs were sensitized to complement factors present in normal human serum to induce the formation of C5b-9 on their plasma membranes.

RESULTS

This triggered an expected abrupt rise in intracellular Ca2+ reflecting membrane leakage. Remarkably, while intracellular Ca2+ remained elevated, membrane leakage ceased within 30 minutes, and cells did not show significant death. Extensive mobilization of Weibel-Palade bodies (WPBs) was observed along with secretion of von Willebrand factor (VWF). The potential role of WPBs and VWF in mitigating complement-mediated damage was examined by comparing the effects of C5b-9 on BOECs derived from von Willebrand disease (VWD) patients expressing reduced amounts of VWF, lacking expression of functional VWF, or lacking both VWF and WPBs. BOECs lacking WPBs were not resistant to complement-mediated damage, but became resistant when transfected to express VWF (and thus WPBs).

CONCLUSION

We conclude that BOECs exposed to C5b-9 attack respond by mobilizing WPBs, which mitigate and repair damage by fusing with the plasma membrane. We propose that a similar cell-specific response may protect the vascular endothelium from complement-mediated damage in vivo.

Influence of blood group, von Willebrand factor levels, and age on factor VIII levels in non-severe haemophilia A

BACKGROUND

Data on the effect of ABO blood group (ABO), von Willebrand factor (VWF) levels, and age on factor VIII (FVIII) in non-severe haemophilia A (HA) is scarce.

OBJECTIVE

To investigate if ABO, VWF levels, and age have an influence on the variability of FVIII levels and consequently on the assessment of severity in non-severe HA.

PATIENTS/METHODS

Eighty-nine patients with non-severe HA and 82 healthy controls were included. Data on ABO was collected and FVIII clotting activity (FVIII:C) with one-stage clotting assay (FVIII:C OSA) and chromogenic substrate assay (FVIII:C CSA), FVIII antigen (FVIII:Ag) and VWF antigen (VWF:Ag) and activity (VWF:Act) were determined.

RESULTS

In HA, FVIII:C OSA and CSA and FVIII:Ag were not different between non-O (n = 42, median 15.5, interquartile range 10.4-24.0; 10.0, 6.8-26.0 and 15.2, 10.7-24.9) and O (n = 47, 14.1, 9.0-23.0; 10.0, 5.0-23.0 and 15.2, 9.3-35.5), whereas in healthy controls, non-O individuals had significantly higher FVIII levels.

FVIII

C showed no relevant correlation with VWF levels in HA, but we observed strong correlations in healthy controls. Age had only a minor influence in HA, but had a considerable impact on FVIII:C in healthy controls. In multivariable regression analysis ABO, VWF:Ag and age were not associated with FVIII:C in HA, whereas this model explained 61.3% of the FVIII:C variance in healthy controls.

CONCLUSIONS

We conclude that in non-severe HA ABO and VWF levels do not substantially influence the variability of FVIII levels and age has only minor effects on it, which is important information for diagnostic procedures.

Successful liver transplant from a hemophilia A donor with no development of hemophilia A in recipient

BACKGROUND

Hemophilia A is an X-linked inherited bleeding disorder caused by deficiency of coagulation factor VIII. Factor VIII is activated as part of the intrinsic coagulation cascade. It plays a crucial role as the cofactor in the intrinsic "tenase" complex activating factor X to assist in clot formation. Absence or mutation of this coagulation factor leads to excessive bleeding. Clinical manifestations of hemophilia relate to bleeding from impaired hemostasis, sequelae from bleeding, or complications of coagulation factor infusion. Diagnostic criteria for Hemophilia A include factor VIII activity level below 40% of normal, presence of a mutated F8 gene, and the absence of von Willebrand disease (F8 gene - Genetics Home Reference - NIH. https://ghr.nlm.nih.gov/gene/F8). Patients who have this intrinsic defect in the coagulation cascade have a characteristically prolonged PTT. It is theorized that the majority of factor VIII is synthesized mainly in the liver, by way of liver sinusoidal endothelial cells (Arruda VR. Haematologica. 2015;100(7):849-850). Extrahepatic production also occurs in the endothelial cells, kidneys, and lymphatic tissue. In 1969, Marchioro et al showed that transplantation of normal liver to hemophilia dog could normalize plasma factor VIII levels (Marchioro T L, Science. 1969;163(3863):188-190). These results were subsequently proven in humans. Liver transplantation from hemophilia A donors without factor VIII inhibitor is not commonly performed due to the perceived risk of developing hemophilia A in the recipient. There is currently limited literature aimed at elucidating this risk. We present a case of liver transplantation in a hemophilia A donor to a recipient with no history of hemophilia A with literature reviewis a case report, objective and method do not apply.

OBJECTIVE AND METHOD

We did a case report and literature review of a liver transplant receipient fro ma hemohpila A donor.

RESULTS

The receipient of the liver from hemophilia A donor did not develop hemophilia post transplant and had normal factor VIII levels.

CONCLUSION

To our knowledge, this is only the second case in humans of hemophilia A patient as a donor in liver transplantation. As the indications for liver transplantation have expanded, there is a need to expand the donor list, and possibly not exclude this population as viable donor option.

Patients with aortic stenosis have von Willebrand factor abnormalities and increased proliferation of endothelial colony forming cells

BACKGROUND

Patients with aortic stenosis (AS) can experience bleeding complications including gastrointestinal bleeding from angiodysplastic lesions due to acquired von Willebrand syndrome. Studies have pointed to a role for von Willebrand factor (VWF) in angiogenesis.

OBJECTIVE

The objective of this study was to assess VWF defects in AS patients over time and the impact on angiogenesis using patient-derived endothelial colony-forming cells (ECFCs).

PATIENTS/METHODS

Plasma sample collection and ECFC isolations were performed before valve replacement surgery, 3 to 5 days after, and 6 months after surgery. Plasma VWF antigen, activity, propeptide, collagen binding, multimers, factor VIII coagulant activity, and ADAMTS13 activity (a disintegrin-like and metalloprotease with thrombospondin type 1 motifs 13) were determined. ECFCs were assessed for VWF and angiopoietin-2 (Ang-2) storage and secretion, cell proliferation, and tubule formation in Matrigel.

RESULTS AND CONCLUSIONS

Aortic stenosis patients exhibited quantitative and qualitative abnormalities of VWF including significantly increased VWF antigen, activity, and propeptide levels following surgery (P < .01). Increased high molecular weight VWF multimers were observed at all time points and in particular 3 to 5 days after surgery (mean = 14% ± 6%) relative to before (mean = 10% ± 4%), suggesting increased proteolysis by ADAMTS13 pre-operatively in a shear-dependent manner. ECFCs from patients with aortic stenosis were more proliferative than controls (P < .05) and had increased retention of Ang-2 (P < .05) suggesting epigenetic modification of the cells. Overall, there are hemostatic changes in AS patients that are present before valve replacement surgery and these persist long after surgery has occurred. These findings have implications for the current clinical management of AS patients.