How I treat type 2B von Willebrand disease.

Type 2B von Willebrand disease (VWD) is an inherited bleeding disorder caused by changes in von Willebrand factor (VWF) that enhance binding of VWF to GPIb on platelets. Although this disorder is seemingly well defined because of this single molecular defect, in reality type 2B VWD is a clinically heterogeneous disorder that can be difficult to identify and manage. Diagnostic criteria include a history of mucocutaneous bleeding, laboratory studies showing enhanced VWF binding of platelets and/or a 2B VWD genetic variant, and a family history consistent with autosomal dominant inheritance. Thrombocytopenia, although not always present, is common and can be exacerbated by physiologic stressors such as pregnancy. The mainstay of therapy for type 2B VWD is VWF replacement therapy. Adjunct therapies useful in other types of VWD, such as antifibrinolytics, are also used in type 2B VWD. 1-Desamino-8-d-arginine vasopressin (DDAVP) is controversial because of exacerbation of thrombocytopenia, but is, in practice, sometimes used for minor bleeding. Here we review the available evidence and provide 3 clinical cases to illustrate the intricacies of diagnosing type 2B VWD to describe the response to DDAVP and to review complexities and management during pregnancy.

Type 2M and Type 2A von Willebrand Disease: Similar but Different.

Analogous to the differentiation between hemophilia A and B, respectively, reflecting deficiency in factor VIII (FVIII) and FIX, and increasing being recognized as reflecting clinically different disorders, types 2A and 2M von Willebrand disease (VWD) can also be shown to express both similarities and differences in their prevalence, genetic defects, laboratory test results, clinical features, and treatment responses. In this narrative review, we explore these two "subtypes" of type 2 VWD, identifying parallels and dissimilarities in various aspects of their presentation to clinicians and to scientists/laboratories. This differential will become increasingly important as we strive to provide personalized approaches to future management of patients with VWD, particularly in the emerging landscape of recombinant von Willebrand factor.

Type 2B von Willebrand Disease: A Matter of Plasma Plus Platelet Abnormality.

Type 2B von Willebrand disease (VWD2B) is a rare, autosomal-dominant inherited bleeding disorder, characterized by an enhanced ristocetin-induced platelet aggregation in platelet-rich plasma and often with variable degree of thrombocytopenia and loss of high-molecular-weight multimers von Willebrand factor (VWF). All these phenomena are caused by a mutant VWF, normally synthesized and assembled by endothelial cells, but with heightened affinity binding to the platelet receptor glycoprotein Ib-α (GpIb-α). When this abnormal VWF is released into the circulation and under specific clinical circumstances, in vivo platelet clumping is observed. Mutations, invariably clustered in exon 28 of the VWF gene encoding for the VWF A1 domain involved in VWF binding to GpIb-α, are responsible for VWD2B phenotype. Clinical and laboratory phenotype appears strongly related to the type of VWF-causative mutations. However, recent evidences suggest that a true platelet defect is also present in this type, with several morphological and functional abnormalities being detected in a subset of VWD2B patients.

Baseline factor VIII plasma levels and age at first bleeding in patients with severe forms of von Willebrand disease.

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder. The age of bleeding onset is highly variable, also in patients with similar degree of severity. AIM: The primary aim of this study was to evaluate whether baseline factor VIII (FVIII) plasma levels correlate with age at first bleeding in patients with extremely low levels of VWF:RCo (<6 IU dL(-1) ). METHODS: One hundred and three patients with VWF:RCo <6 IU dL(-1) (6 VWD1, 73 VWD2 and 24 VWD3) undergoing a medical examination between September 2010 and September 2013 were included. The relationship between baseline FVIII levels and age at first bleeding was tested in a multivariable linear regression model, adjusting for sex. RESULTS: The median age at first bleeding was lower in patients with VWD3 than in those with severe forms of VWD1 or VWD2 (1 year vs. 7 and 8 years, respectively, P < 0.0001). A positive non-linear relationship between FVIII levels and age at first bleeding was found, the latter increasing by 5 years for every 10 IU dL(-1) increase of FVIII (ß = 4.95 [95% CI: 2.02-7.87]) until levels of 30 IU dL(-1) , after which the age increased slowly. This relationship was not found in VWD 2A and 2B. In 65 patients (63%) there was a more than 6-month delay between bleeding onset and VWD diagnosis, with no difference over decades. CONCLUSIONS: Baseline FVIII plasma levels influence the age at bleeding onset in VWD patients with extremely low levels of VWF:RCo, except in those with types 2A and 2B.

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

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

Spectrum of Von Willebrand's disease in Punjab: clinical features and types.

BACKGROUND: Von Willebrand's disease (VWD) is a common inherited bleeding disorder caused by quantitative deficiency (Type-1 & Type-3 VWD) or qualitative defect of Von Willebrand's Factor (Type-2 VWD). Regarding VWD limited studies are available in Pakistan. The current study was aimed to determine the clinical presentation and frequency of types of VWD. METHODS: A cross sectional study was carried out from 16th December 2012 to 15th December 2013 on fifty one patients of VWD. RESULTS: Patients were diagnosed on the basis of prolonged bleeding time, abnormal APTT, reduced level of VWF: Ag, FVIII, VWF: RCo and ratio of VWF: RCo/VWF Ag. Among them 26 (50.98%) were male and 25 (49.02%) were female. Type3 VWD (94.12%) was found to be the commonest type. Two (3.92%) cases of type-2 VWD and only one (1.96%) case of type-1 VWD were identified. Easy bruising was the most commonly observed clinical presentation, 21 (41.18%) patients, followed by epistaxis 7 (13.73%), gum bleed 4(7.84%) menorrhagia 5(9.80%), haemarthosis 2(3.92%), haematoma formation 5 (9.80%), bleeding after circumcision 2 (3.92%), bleeding after surgery 2 (3.92%) and umbilical cord bleeding 3 (5.88%). Consanguineous marriages were reported in parents of 42 (82.4%) patients. Family history of bleeding disorder was reported in 44 (86.27%) of cases. CONCLUSION: Type-3 VWD was found to be the commonest type which can be attributed to the fact that type-3 VWD is transmitted through autosomal recessive pattern of inheritance and consanguineous marriages are highly practiced in our society leading to high frequency of this form of VWD. Easy bruising and epistaxis were concluded to be the most common clinical presentation. Menorrhagia was found to be common in the females of child bearing age.

Type 2N von Willebrand disease: genotype drives different bleeding phenotypes and treatment needs.

BACKGROUND: Type 2 Normandy von Willebrand disease (VWD2N) is usually perceived as a mild bleeding disorder that can be treated with desmopressin (DDAVP). However, VWD2N patients can be compound heterozygous or homozygous for different variants, with p.Arg854Gln (R854Q) being the most frequent causative one. There are limited data about the impact of 2N variants on VWD2N phenotype and DDAVP response. OBJECTIVES: This study aims to describe the phenotype of VWD2N, including DDAVP response, according to genotype. METHODS: VWD2N patients with a complete genotype/phenotype characterization by the French reference center for VWD, including MCMDM-1VWD bleeding score, were eligible to be included in the study. Results of the DDAVP trial were also collected. RESULTS: A total of 123 VWD2N patients from the French registry were included in this study. Results were stratified according to the presence (R854QPos, n = 114) or absence (R854QNeg, n = 9) of at least 1 R854Q allele. Three R854QPos subgroups were further individualized: patients homozygous (R854QHmz, n = 55), compound heterozygous for R854Q and a null allele (R854Q/3, n = 48), or compound heterozygous for R854Q and another 2N variant (R854Q/2N, n = 11). FVIII: C levels were significantly lower in R854QNeg and R854Q/3 patients compared with R854QHmz ones (P < .001 and P < .0001, respectively). R854QNeg patients were diagnosed earlier due to bleeding symptoms and had a higher bleeding score than R854QPos patients (P < .001). In DDAVP trial, FVIII:C survival was lower in VWD type 2N than in type 1 patients. R854QPos patients had a heterogeneous DDAVP response, which was best predicted by baseline FVIII:C level. CONCLUSION: The heterogeneous genetic background of VWD2N drives different bleeding phenotypes and response patterns to DDAVP, underlining the clinical relevance of DDAVP trial to identify patients potentially eligible to alternative therapeutic options.

Gain-of-function GPIb ELISA assay for VWF activity in the Zimmerman Program for the Molecular and Clinical Biology of VWD.

von Willebrand disease (VWD) is a common bleeding disorder, but diagnosis is sometimes challenging because of issues with the current von Willebrand factor (VWF) assays, VWF antigen (VWF:Ag) and VWF ristocetin cofactor activity (VWF:RCo), used for diagnosis. We evaluated 113 healthy controls and 164 VWD subjects enrolled in the T.S. Zimmerman Program for the Molecular and Clinical Biology of VWD for VWF:Ag, VWF:RCo, and a new enzyme-linked immunosorbent assay (ELISA)-based assay of VWF-glycoprotein Ib (GPIb) interactions using a gain-of-function GPIb construct (tGPIbα(235Y;239V)) as a receptor to bind its ligand VWF in an assay independent of ristocetin (VWF:IbCo ELISA). Healthy controls, type 1, 2A, 2M, and 2N subjects had VWF:RCo/VWF:Ag ratios similar to the ratio obtained with VWF:IbCo ELISA/VWF:Ag. Type 2B VWD subjects, however, had elevated VWF:IbCo ELISA/VWF:Ag ratios. Type 3 VWD subjects had undetectable (< 1.6 U/dL) VWF:IbCo ELISA values. As previously reported, VWF:RCo/VWF:Ag ratio was decreased with a common A1 domain polymorphism, D1472H, as was direct binding to ristocetin for a 1472H A1 loop construct. The VWF:IbCo ELISA, however, was not affected by D1472H. The VWF:IbCo ELISA may be useful in testing VWF binding to GPIb, discrimination of type 2 variants, and in the diagnosis of VWD as it avoids some of the pitfalls of VWF:RCo assays.

Clinical measurement of von Willebrand factor by fluorescence correlation spectroscopy.

BACKGROUND: Identification of von Willebrand factor (vWF) abnormalities in a variety of conditions is hampered by the limitations of currently available diagnostic tests. Although direct multimer visualization by immunoelectrophoresis is a commonly used method, it is impractical as a routine clinical test. In this study, we used a biophysical analysis tool, fluorescence correlation spectroscopy (FCS), to measure vWF distributions. The goals were to develop a method that is quicker and simpler than vWF gel electrophoresis and to evaluate the potential of FCS as a clinical diagnostic technique. METHODS: We analyzed plasma from 12 patients with type 1 von Willebrand disease (vWD), 14 patients with type 2 vWD, and 10 healthy controls using a fluctuation-based immunoassay approach. RESULTS: FCS enabled identification and proper classification of type 1 and type 2 vWD, producing quantitative results that correspond to qualitative gel multimer patterns. FCS required minimal sample preparation and only a 5-min analysis time. CONCLUSIONS: This study represents the first implementation of FCS for clinical diagnostics directly on human plasma. The technique shows potential for further vWF studies and as a generally applicable laboratory test method.

The mutation N528S in the von Willebrand factor (VWF) propeptide causes defective multimerization and storage of VWF.

We characterized a consanguineous Turkish family suffering from von Willebrand disease (VWD) with significant mucocutaneous and joint bleeding. The relative reduction of large plasma von Willebrand factor (VWF) multimers and the absent VWF triplet structure was consistent with type 2A (phenotype IIC) VWD. Surprisingly, platelet VWF was completely deficient of multimers beyond the VWF protomer, suggesting defective alpha-granular storage of larger multimers. Patients were nearly unresponsive to desmopressin acetate, consistent with a lack of regulated VWF release from endothelial cell Weibel-Palade bodies, suggesting defective storage also in endothelial cells. We identified an N528S homozygous mutation in the VWF propeptide D2 domain, predicting the introduction of an additional N-glycosylation site at amino acid 526 in close vicinity to a "CGLC" disulphide isomerase consensus sequence. Expression studies in mammalian cells demonstrated that N528S-VWF was neither normally multimerized nor trafficked to storage granules. However, propeptide containing the N528S mutation trafficked normally to storage granules. Our data indicate that the patients' phenotype is the result of defective multimerization, storage, and secretion. In addition, we have identified a potentially novel pathogenic mechanism of VWD, namely a transportation and storage defect of mature VWF due to defective interaction with its transporter, the mutant propeptide.

Abnormal VWF modifies megakaryocytopoiesis: studies of platelets and megakaryocyte cultures from patients with von Willebrand disease type 2B.

von Willebrand factor (VWF) is an essential mediator of platelet adhesion to the vessel wall, but little is known about its role in megakaryocytopoiesis. VWF and its platelet receptor, glycoprotein Ibalpha (GPIbalpha), are both expressed during megakaryocyte (MK) maturation. This study was designed to evaluate whether the enhanced VWF-GPIbalpha interactions typical of patients with von Willebrand disease type 2B (VWD2B) modify platelet production. Platelets from 9 patients with VWD2B with 7 different gain-of-function mutations were examined by electron microscopy (EM) and immunofluorescence labeling. For the patients with VWD2B, EM characteristically showed variable numbers of structurally abnormal giant platelets, sometimes in agglutinates. Cultures of MKs from controls performed with or without purified VWF confirmed a positive influence of VWF on platelet production with specific inhibition by an antibody blocking VWF binding to GPIbalpha. VWD2B MK cultures examined by EM showed a disorganized demarcation membrane system and abnormal granule distribution. They produced platelets with structural abnormalities typical of VWD2B. Confocal examination of MK revealed limited extension of pseudopods with few large proplatelets. These results confirm that megakaryocytopoiesis is modified by the enhanced VWF-GPIbalpha interactions. These data obtained for controls and patients with VWD2B suggest a novel regulatory role of VWF-GPIbalpha interactions in platelet production.

Pregnancy in type 2B VWD: a case series.

Type 2B von Willebrand disease (VWD) is a rare, inherited bleeding disorder resulting from a qualitative defect in von Willebrand factor (VWF). There is very little published information on how to quantify bleeding risk and manage haemostasis in type 2B VWD patients during pregnancy. This article presents the changes in VWF parameters and details of patient management and delivery outcomes for four pregnancies in three women with two different mutations causing type 2B VWD. We report an unexpected rise in the VWF:Ag at 37 weeks gestation in two sisters with R1306W associated with significant thrombocytopenia. These patients were supported with platelet transfusions as well as intermediate purity VWF-FVIII plasma concentrates during the peri- and postpartum periods. No thrombocytopenia was observed in our third case with a mutation encoding an R1308C substitution; haemostatic support was with intermediate purity VWF-FVIII plasma concentrates alone. No adverse bleeding events occurred and in all cases a live healthy infant was delivered. One patient was readmitted post partum with bleeding symptoms due to retained placenta; no further haemostatic support was given at this time. This case series is the first to detail the progression of laboratory parameters, management and outcomes of pregnancy in patients with type 2B VWD. The cases illustrate some of the challenges posed by the increased production of a VWF variant with a gain-of-function effect. The rapid coagulation changes observed in this series illustrate the need for continual monitoring of VWF parameters and platelet count throughout pregnancy in women with type 2B VWD.

Biochemical and molecular characterization of von Willebrand disease type 2N in a pregnant patient who gave birth under analgesia with remifentanil.

von Willebrand 's disease (vWD) is the commonest inherited bleeding disorder. Although in literature there are some cases reported of epidural analgesia for labor pain in pregnancies with Von Willebrand's disease, the technique is not free from risk of neurolocal complications. Authors reported a case of spontaneous labor in a pregnant woman with type II vWD, delivered under local analgesia administered through a continuous intravenous infusion of remifentanil integrated by boli. A 34-year-old woman at the 39th week of her second pregnancy was admitted for an active labor of a single fetus in cephalic presentation. The patient had been diagnosed with type II vWD by a hematologist during her first pregnancy. The patient coagulation panel was as follows: a reduction of VIIIth factor concentration (21 percent); a normal value of vWD functional assay; an increase of vWf:Ag (antigen) and a reduction of XIth factor. During labor she was put on remifentanil in PCA (patient controlled analgesia), administered with slow boli followed by continuous infusions at increasing doses. The woman delivered a female fetus weighing 3,550 g, in vertex presentation, in left anterior occipital position, with an A.P.G.A.R. of 8 at the first minute and 9 at the fifth minute. The total duration of labor was 3 hours and 10 minutes. The patient was satisfied with analgesia in labor. The bleeding during and after delivery was regular. In the authors ' opinion, it is important to know that an alternative to epidural analgesia can be used in order to avoid the risk of neurological complications in labor pain for patients with type II Von Willebrand's disease.

Acquired type 2A von Willebrand syndrome caused by aortic valve disease corrects during valve surgery.

BACKGROUND: Aortic valve (AV) defects can destroy high molecular weight multimers (HMWM) of von Willebrand factor (VWF), leading to acquired von Willebrand syndrome (aVWS) type IIA. This syndrome is considered a cause for increased perioperative bleeding in AV surgery. If diagnosed before operation, administration of VWF/FVIII concentrates is recommended. However, there is currently no evidence that the VWF HMWM defect persists during surgery long enough to require haemostatic therapy. We hypothesized that the preoperative VWF HMWM defect corrects already during cardiopulmonary bypass (CPB) before any haemostatic therapy. METHODS: This prospective observational study enrolled 17 patients undergoing AV surgery, either isolated or associated with mitral valve or aorta surgery, and also 10 patients undergoing coronary artery bypass surgery (CABG) for comparison. VWF HMWM, VWF antigen (VWF:Ag) concentration, and collagen-binding capacity (VWF:CB) were measured before operation, directly after weaning from CPB, and on the first postoperative day. RESULTS: In 12 of the 17 subjects undergoing AV surgery (71%), VWF HMWM were abnormally absent before operation. At the end of CPB, VWF HMWM were normal in 15 of AV subjects (88%), and was normal in 16 subjects on the first postoperative day. VWF:Ag and VWF:CB were within or above the normal range at all three times. Two out of 10 subjects undergoing CABG (20%) had preoperative deficits of VWF HMWM that normalized after operation. CONCLUSIONS: Preoperative VWF HMWM defects corrected at the end of CPB in the absence of haemostatic therapy in most patients undergoing AV surgery. Diffuse bleeding occurring after CPB is unlikely to be related to persisting type 2A von Willebrand syndrome; other causes of coagulopathy should be suspected. Administration of VWF/FVIII concentrates appears unnecessary in this setting.

[Acquired von Willebrand's disease type 2A following arteriovenous fistula for haemodialysis?]. / Erworbenes von-Willebrand-Syndrom Typ 2A als Begleiterscheinung eines Dialyseshunts?

Acquired von Willebrand's disease (aVWD) is considered to be an underestimated cause of unexplained bleeding. Adsorption of von Willebrand factor (VWF) to tumour cells or hydroxyethyl starch and elimination of VWF by autoantibodies as well as shear stress-induced mechanical alteration of VWF with concomitant cleavage by enzymes may lead to an acquired deficiency of VWF and a bleeding disorder. We report a 39-year-old woman who developed spontaneous bleeding five years after surgical creation of an arteriovenous fistula (AVF) for haemodialysis treatment. AVWD type 2A was diagnosed after successful renal transplantation. One year after surgical closure of the AVF, the aVWD could not be verified again. Thus, the aVWD may have developed because of altered blood flow and shear stress inside the arteriovenous fistula.

2B or not 2B? A diagnosis of von Willebrand disease a lifetime of 86 years in the making.

Type 2B von Willebrand disease (2B VWD) is a rare, autosomal dominant bleeding disorder characterized by a hyperadhesive form of von Willebrand factor (VWF). 2B VWD expresses phenotypically as an enhanced ristocetin-induced platelet aggregation and usually also a discordance in VWF activity versus protein level, with loss of high molecular weight VWF and (mild) thrombocytopenia. While all cases of 2B VWD supposedly share these characteristics, there is significant heterogeneity in laboratory findings within this group of patients, which are largely dictated by the underlying genetic defect. We present a case of such a patient, expressing a clearly atypical VWF phenotype, but as still associated with enhanced ristocetin-induced platelet aggregation, thrombocytopenia, and a previously undescribed VWF variant (c.4130C>G; p.Ala1377Gly). The patient was misdiagnosed over his lifetime as idiotypic thrombocytopenia - a (mis)diagnosis that took a lifetime of 86 years to redress.