How much do we really know about von Willebrand disease?

Modulation of Haemostatic Balance in Combined von Willebrand Disease and Antithrombin Deficiency: A Comprehensive Family Study

INTRODUCTION

Maintaining the balance between procoagulant and anticoagulant factors is essential for effective haemostasis. Emerging evidence suggests a modulation of bleeding tendency by factors in the anticoagulant and fibrinolytic systems.

AIM

This study investigates the clinical and laboratory characteristics of a family with combined von Willebrand disease (VWD) and antithrombin (AT) deficiency.

METHODS

The study focused on a 38-year-old female index patient (IP) with severe type 3 VWD and a history of bleeding disorders. Coagulation assays included VWF antigen, platelet-dependent VWF activity, factor VIII activity, thrombin generation assay (TGA) and AT activity. Molecular genetic analyses were conducted by a targeted DNA custom next generation sequencing (NGS) panel.

RESULTS

The IP and one of her sisters suffered type 3 VWD. While the IP presents with a classical severe bleeding phenotype, the sister (II-2) exhibited less severe bleeding symptoms. Extended family members showed type 1 VWD with mild presentations. NGS revealed a homozygous deletion of exon 6 in the VWF gene in the IP and her sister (II-2). All other family members carry this genetic variant in a heterozygous state. Additionally, II-2 has a heterozygous variant in the SERPINC1 gene (c.133C>T, p.Arg45Trp). Both IP and II-2 carry a homozygous prothrombin G20210A variant. TGA results indicated reduced thrombin generation in severe VWD patients, with a pronounced thrombin burst in those with the AT and prothrombin G20210A variant.

CONCLUSIONS

AT deficiency appears to modulate bleeding symptoms in severe VWD. This study emphasizes the importance of comprehensive genetic and phenotypic evaluation in managing complex coagulation disorders.

Acquired von Willebrand Syndrome Secondary to Normally Functioning Mechanical Aortic Valve and High-Output Cardiac State

Acquired von Willebrand syndrome (AVWS) is caused by an acquired deficiency of von Willebrand factor (VWF), a multimeric protein required for primary hemostasis. For patients with heart valve diseases, high gradient across the malfunctioning valves could cause elevated shear stress and damage the most effective large VWF, eventually resulting in AVWS. However, AVWS has not been reported in association with normally functioning mechanical valves. Herein, we reported a 74-year-old female who suffered from recurrent gastrointestinal bleeding with a history of mechanical aortic and mitral valve replacement. This patient's function/antigen ratio of VWF was decreased and gel electrophoresis revealed the loss of large VWF, which confirmed the diagnosis of AVWS. Echocardiogram showed that the function of the prostheses was normal. However, the gradient across aortic valve was increased due to a high cardiac state which is secondary to chronic anemia, resulting in the disruption of large VWF multimers and exacerbation of gastrointestinal (GI) bleeding. After managing the patient's anemia with transfusion, the gradient across the aortic valve had improved, with the resolution of GI bleeding. This is the first case report of AVWS that is associated with a normally functioning mechanical valve. AVWS should be considered one of the differential diagnoses if patients present with unexplained GI bleeding on the background of having prosthetic heart valves. The management of the underlying condition is essential.

Clinical and laboratory presentation of von Willebrand disease: Experience from a single center in KSA

Objectives

This study was aimed at assessing the clinical presentations and laboratory findings among patients diagnosed with vWD at a Saudi tertiary care unit.

Methods

This retrospective study included 189 patients with vWD who were followed up in our unit over 4 years. Clinical and laboratory data were collected and analyzed in SPSS.

Results

The median age of the study cohort was 30 years (range 11 months-56 years). The cohort had a female preponderance, with 32.30% males and 66.70% females. Bleeding from different sites was observed, mostly from the joints and muscles (23.90%), followed by the mucus membranes (14.60%), genitourinary areas (7.70%), ecchymoses (2.80%), and gastrointestinal areas (2.80%). A total of 48% of participants presented with more than one type of bleeding. A total of 105 (58.01%) participants had type 1; 29 (16.02%) had type 2; and 47 (25.96%) had type 3 vWD. Blood tests indicated the following mean value: hemoglobin, 116 ± 25.60 gm/L; ferritin, 75.80 ± 166.80 μg/L (median 28.5); vWAg, 0.40 ± 0.27IU/ml; and vWD:RCo, 0.32 ± 0.20IU/dL. The partial thromboplastin time was prolonged in 49.20% and normal in 50.80% of participants. Platelet function analysis values were prolonged in 92.90% and normal in 7.10% of participants. Comparative analysis of the O-type and non-O blood type showed that blood type O was significantly correlated with factor VIII (p-value = 0.013), vWF:RCo (p-value = 0.004), and vWF:Ag (p-value = 0.019).

Conclusion

Joint and muscle bleeds were the most common clinical presentations in our cohort. Although type 1 vWD was most prevalent in our cohort, we observed a comparatively higher prevalence of type 3, possibly because of ethnic differences or referral bias. We found a significant difference between O and non-O blood type regarding FVIII and vWF:Ag, and observed a more pronounced difference for vWD activity measuresd by vWF:RCo with blood type O being the systematic factor.

IX international curse of continuing formation in haemophilia and other congenital coagulopathies. The role of the Laboratory in coagulation disorders. Diagnosis of von Willebrand disease

Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (VWF). This protein far from simplicity constitutes a very complex molecular model, remaining unravelled yet many aspects of it, even though the VWF gene (VWF) was cloned already in 1985 and the structure of VWF well defined. VWD diagnosis is difficult to achieve in a significant proportion of patients due to both disease heterogeneity and limitations in existing test processes. The cornerstone of diagnosis relies on interpretation of VWF test results, the presence of clinical manifestations of bleeding, especially mucocutaneous, and (in most cases) a positive family history. However, even with a significant bleeding history, a family history may not be positive due to factors of incomplete penetrance and variable expressivity that affect genetic changes. The laboratory diagnosis of VWD can be difficult, as the disease is heterogeneous and an array of assays is required to describe the phenotype. Basic classification of quantitative (type 1 and 3) and qualitative (type 2 variants) VWD requires determination of VWF antigenic (VWF:Ag) levels and assaying of VWF ristocetin cofactor (VWF:RCo) activity. The latter is required for identifying and subtyping VWD, but the assay is poorly standardized. For that reason, novel VWF activity assays have been developed awaiting more extensive comparison data between different methodologies and requiring validation on larger patient series. The qualitative type 2 VWF deficiency can be further divided into four different subtypes (A, B, M and N) using specific assays that measure other activities or the size distribution of VWF multimers. However, frequently, it may be difficult to correctly classify the VWD phenotype, and genetic analysis is through mutation identification may provide a tool to clarify the disorder.

Understanding the risks of total hip arthroplasty in patients with von Willebrand’s disease

Purpose:

Patients with von Willebrand’s disease (VWD) have either a qualitative or quantitative deficiency in a key clotting protein called von Willebrand’s factor. Type Ⅰ disease is the most common variant, but its clinical implications in total hip arthroplasty (THA) are unclear. Our purpose is to describe the perioperative impact of VWD in THA.

Methods:

We retrospectively reviewed a total of 17 primary THAs in 14 patients with type Ⅰ VWD performed between 2008 and 2019. Almost all cases (88%) received tranexamic acid, and most (59%) received DDAVP. All patients had a direct anterior approach (DAA) THA.

Results:

None of these cases required a blood transfusion. Mean estimated blood loss was 229 mL, and the mean hemoglobin dropped from 13.9 g/dL to 10.2 g/dL. There were no major bleeding complications. After a mean follow-up of 4 years, the mean hip disability and osteoarthritis outcome score, junior (HOOS, JR) was 79, and there were no reoperations or revisions for any cause.

Conclusion:

Patients with type Ⅰ VWD do not experience severe bleeding with routine chemoprophylaxis combined with DAA THA.

The scavenger receptor SCARA5 is an endocytic receptor for von Willebrand factor expressed by littoral cells in the human spleen

BACKGROUND

Scavenger receptors play a significant role in clearing aged proteins from the plasma, including the large glycoprotein coagulation factors von Willebrand factor (VWF) and factor VIII (FVIII). A large genome-wide association study meta-analysis has identified genetic variants in the gene SCARA5, which encodes the class A scavenger receptor SCARA5, as being associated with plasma levels of VWF and FVIII.

OBJECTIVES

The ability of SCARA5 to regulate the clearance of VWF-FVIII was characterized.

METHODS

VWF-FVIII interactions with SCARA5 were evaluated by solid phase binding assays and in vitro cell based assays. The influence of SCARA5 deficiency on VWF:Ag and half-life was assessed in a murine model. The expression pattern of SCARA5 and its colocalization with VWF was evaluated in human tissues.

RESULTS

VWF and the VWF-FVIII complex bound to human recombinant SCARA5 in a dose- and calcium-dependent manner. SCARA5 expressing HEK 293T cells bound and internalized VWF and the VWF-FVIII complex into early endosomes. In vivo, SCARA5 deficiency had a modest influence on the half-life of human VWF. mRNA analysis and immunohistochemistry determined that human SCARA5 is expressed in kidney podocytes and the red pulp, white pulp, and marginal zone of the spleen. VWF was found to colocalize with SCARA5 expressed by littoral cells lining the red pulp of the human spleen.

CONCLUSIONS

SCARA5 is an adhesive and endocytic receptor for VWF. In human tissues, SCARA5 is expressed by kidney podocytes and splenic littoral endothelial cells. SCARA5 may have a modest influence on VWF clearance in humans.

Von Willebrand factor contribution to pathophysiology outside of von Willebrand disease

VWF is a procoagulant protein that plays a central role in the initiation of platelets aggregate formation and thrombosis. While von Willebrand disease has long been known to result from qualitative and quantitative deficiencies of VWF, it is recently that contribution of elevated levels of VWF to various pathological conditions including thrombosis, inflammation, angiogenesis, and cancer metastasis has been appreciated. Here, we discuss contribution of elevated levels of VWF to various thrombotic and nonthrombotic pathological conditions.