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Contains fulltext : 282506.pdf (Publisher’s version ) (Open Access) Patients with type 1 and type 2 von Willebrand disease (VWD) can be treated with desmopressin. Although a previous study has shown that the location of the causative VWF gene variant is associated with desmopressin response in type 1 VWD, the association between variants in the VWF gene and desmopressin response is not yet fully understood. Our primary aim was to compare desmopressin response in type 1 VWD patients with and without a VWF gene variant. Secondly, we investigated whether desmopressin response depends on specific VWF gene variants in type 1 and type 2 VWD. We included 250 patients from the Willebrand in the Netherlands study: 72 type 1 without a VWF gene variant, 108 type 1 with a variant, 45 type 2A, 16 type 2M, and 9 type 2N patients. VWF gene was analyzed with ion semiconductor sequencing and Multiplex Ligation-dependent Probe Amplification. Complete response to desmopressin was observed in all type 1 VWD patients without a variant, 64.3% of type 1 patients with a variant, and 31.3% of type 2 patients (P < .001). Despite a large interindividual variability in desmopressin response, patients with the same variant had comparable desmopressin responses. For instance, in 6 type 1 patients with exon 4 to 5 deletion, mean VWF activity at 1 hour after desmopressin was 0.81 IU/mL, with a coefficient of variation of 22.9%. In conclusion, all type 1 VWD patients without a VWF gene variant respond to desmopressin. In type 1 and type 2 VWD patients with a VWF variant, desmopressin response highly depends on the VWF gene variants.

Genotyping is not routinely performed at diagnosis of von Willebrand disease (VWD). Therefore, the association between genetic variants and pathogenic mechanism or the clinical and laboratory phenotype is unknown in most patients, especially in type 1 VWD. To investigate whether genotyping adds to a better understanding of the pathogenic mechanisms and variability in phenotype, we analyzed the VWF gene in 390 well-defined VWD patients, included in the WiN study. A VWF gene variant was found in 155 patients (61.5%) with type 1, 122 patients (98.4%) with type 2, and 14 patients (100%) with type 3 VWD. Forty-eight variants were novel. For each VWF gene variant, the pathogenic mechanisms associated with reduced VWF levels was investigated using the FVIII:C/VWF:Ag and VWFpp/VWF:Ag ratios. In type 1 VWD, reduced synthesis or secretion of VWF was most frequently found in patients with nonsense variants, frameshift variants, and deletions, whereas rapid clearance of VWF was mainly found in patients with missense variants. Furthermore, type 1 VWD patients with and without a VWF gene variant were clearly distinct in their clinical features such as age of diagnosis, laboratory phenotype, and bleeding phenotype. In type 2 VWD, 81% of variants were associated with an increased clearance of VWF. To conclude, we identified the pathogenic mechanisms associated with various VWF gene variants in type 1, 2, and 3 VWD patients. Additionally, major differences in the phenotype of type 1 VWD patients with and without a variant were observed, which may be of importance for clinical management.

BACKGROUND: In patients with non-severe hemophilia A, we lack detailed knowledge on the timing of treatment with factor VIII (FVIII) concentrates. This knowledge could provide information about the expected treatment timing in patients with severe hemophilia A treated with non-replacement therapies. OBJECTIVE: To assess the FVIII treatment history in patients with non-severe hemophilia A. METHODS: Patients with non-severe hemophilia (baseline FVIII activity [FVIII:C] 2-40 IU/dL) were included from the INSIGHT study. The primary outcome was median age at first FVIII exposure (ED1). In a subgroup of patients for whom more detailed information was available, we analyzed the secondary outcomes: median age at first 20 EDs, annualized bleeding rate for all bleeds (ABR), joint bleeds (AJBR), and major spontaneous bleeds (ASmBR). RESULTS: In the total cohort (n = 1013), median baseline FVIII activity was 8 IU/dL (interquartile range [IQR] 4-15) and the median age at ED1 was 3.7 years (IQR 1.4-7.7). Median age at ED1 rose from 2.5 years (IQR 1.2-5.7) in patients with FVIII:C 2-5 IU/dL to 9.7 years (IQR 4.8-16.0) in patients with FVIII:C 25-40 IU/dL. In the subgroup (n = 104), median age at ED1, ED5, ED10, and ED20 was 4.0 years (IQR 1.4-7.6), 5.6 years (IQR 2.9-9.3), 7.5 years (IQR 4.4-11.3), and 10.2 years (IQR 6.5-14.2), respectively. Median ABR, AJBR, and ASmBR were 1.1 (IQR 0.5-2.6), 0.3 (IQR 0.1-0.7), and 0 (IQR 0-0), respectively. CONCLUSION: This study demonstrates that in non-severe hemophilia A, the age at first FVIII exposure increases with baseline FVIII:C and that major spontaneous bleeds rarely occur. ispartof: JOURNAL OF THROMBOSIS AND HAEMOSTASIS vol:18 issue:12 pages:3203-3210 ispartof: location:England status: published

Contains fulltext : 282574.pdf (Publisher’s version ) (Open Access) Von Willebrand disease (VWD) is a bleeding disorder caused by quantitative (type 1 or 3) or qualitative (type 2A/2B/2M/2N) defects of circulating von Willebrand factor (VWF). Circulating VWF levels not always fully explain bleeding phenotypes, suggesting a role for alternative factors, like platelets. Here, we investigated platelet factor 4 (PF4) in a large cohort of patients with VWD. PF4 levels were lower in type 2B and current bleeding phenotype was significantly associated with higher PF4 levels, particularly in type 1 VWD. Based on our findings we speculate that platelet degranulation and cargo release may play a role across VWD subtypes.

In light of the rapidly changing landscape of haemophilia treatment, the authors of the position paper on the “European Principles of Inhibitor Management” published in 2018 (Table 1) [1] now provide an update on the major impact of novel therapies that bypass and/or substitute clotting factor VIII (FVIII) and IX (FIX) in the care of haemophilia patients with FVIII- or FIX-neutralizing allo-inhibitory antibodies (inhibitors). [...]

Background von Willebrand factor (VWF) is crucial for optimal dosing of factor VIII (FVIII) concentrate in hemophilia A patients as it protects FVIII from premature clearance. To date, it is unknown how VWF behaves and what its impact is on FVIII clearance in the perioperative setting. Aim To investigate VWF kinetics (VWF antigen [VWF:Ag]), VWF glycoprotein Ib binding (VWF:GPIbM), and VWF propeptide (VWFpp) in severe and moderate perioperative hemophilia A patients included in the randomized controlled perioperative OPTI-CLOT trial. Methods Linear mixed effects modeling was applied to analyze VWF kinetics. One-way and two-way analyses of variance were used to investigate perioperative VWFpp/VWF:Ag ratios and associations with surgical bleeding. Results Fifty-nine patients with median age of 48.8 years (interquartile range: 34.8–60.0) were included. VWF:Ag and VWF:GPIbM increased significantly postoperatively. Blood type non-O or medium risk surgery were associated with higher VWF:Ag and VWF:GPIbM levels compared with blood type O and low risk surgery. VWFpp/VWF:Ag was significantly higher immediately after surgery than 32 to 57 hours after surgery (p Conclusion VWF:Ag and VWF:GPIbM levels increase postoperatively, most significantly in patients with blood type non-O or medium risk surgery. Lower VWF antigen levels did not lead to clinically relevant higher FVIII clearance. VWF:Ag or VWF:GPIbM levels were not associated with perioperative hemorrhage.

Contains fulltext : 218302.pdf (Publisher’s version ) (Open Access) INTRODUCTION: Many patients with von Willebrand disease (VWD) are treated on demand with von Willebrand factor and factor VIII (FVIII) containing concentrates present with VWF and/or FVIII plasma levels outside set target levels. This carries a risk for bleeding and potentially for thrombosis. Development of a population pharmacokinetic (PK) model based on FVIII levels is a first step to more accurate on-demand perioperative dosing of this concentrate. METHODS: Patients with VWD undergoing surgery in Academic Haemophilia Treatment Centers in the Netherlands between 2000 and 2018 treated with a FVIII/VWF plasma-derived concentrate (Haemate(R) P/Humate P(R)) were included in this study. Population PK modeling was based on measured FVIII levels using nonlinear mixed-effects modeling (NONMEM). RESULTS: The population PK model was developed using 684 plasma FVIII measurements of 97 VWD patients undergoing 141 surgeries. Subsequently, the model was externally validated and reestimated with independent clinical data from 20 additional patients undergoing 31 surgeries and 208 plasma measurements of FVIII. The observed PK profiles were best described using a one-compartment model. Typical values for volume of distribution and clearance were 3.28 L/70 kg and 0.037 L/h/70 kg. Increased VWF activity, decreased physical status according to American Society of Anesthesiologists (ASA) classification (ASA class >2), and increased duration of surgery were associated with decreased FVIII clearance. CONCLUSION: This population PK model derived from real world data adequately describes FVIII levels following perioperative administration of the FVIII/VWF plasma-derived concentrate (Haemate((R)) P/Humate P((R)) ) and will help to facilitate future dosing in VWD patients.

Contains fulltext : 248809.pdf (Publisher’s version ) (Open Access) INTRODUCTION: The negative impact of haemophilia on social participation is well established in previous studies, however, the impact of Von Willebrand disease (VWD) on social participation has not been studied. AIM: To compare the social participation of a large cohort of VWD patients in the Netherlands with the general Dutch population. In addition, to identify factors associated with social participation in VWD. METHODS: Patients participating in the "Willebrand in the Netherlands" study completed an extensive questionnaire on educational level, absenteeism from school or work, and occupational disabilities. RESULTS: Seven-hundred and eighty-eight VWD patients were included (mean age 38.9 years, 59.5% females), of whom 136 children