Type 2B von Willebrand Disease in Pregnancy: A Systematic Literature Review

Type 2B von Willebrand disease mutations differentially perturb autoinhibition of the A1 domain

Type 2B von Willebrand disease (VWD) is an inherited bleeding disorder in which a subset of point mutations in the von Willebrand factor (VWF) A1 domain and recently identified autoinhibitory module (AIM) cause spontaneous binding to glycoprotein Ibα (GPIbα) on the platelet surface. All reported type 2B VWD mutations share this enhanced binding; however, type 2B VWD manifests as variable bleeding complications and platelet levels in patients, depending on the underlying mutation. Understanding how these mutations localizing to a similar region can result in such disparate patient outcomes is essential for detailing our understanding of VWF regulatory and activation mechanisms. In this study, we produced recombinant glycosylated AIM-A1 fragments bearing type 2B VWD mutations and examined how each mutation affects the A1 domain's thermodynamic stability, conformational dynamics, and biomechanical regulation of the AIM. We found that the A1 domain with mutations associated with severe bleeding occupy a higher affinity state correlating with enhanced flexibility in the secondary GPIbα-binding sites. Conversely, mutation P1266L, associated with normal platelet levels, has similar proportions of high-affinity molecules to wild-type (WT) but shares regions of solvent accessibility with both WT and other type 2B VWD mutations. V1316M exhibited exceptional instability and solvent exposure compared with all variants. Lastly, examination of the mechanical stability of each variant revealed variable AIM unfolding. Together, these studies illustrate that the heterogeneity among type 2B VWD mutations is evident in AIM-A1 fragments.

Beyond the guidelines: how we approach challenging scenarios in the diagnosis and management of von Willebrand disease

Although von Willebrand disease (VWD) is the most common inherited bleeding disorder, its diagnosis and management are often challenging. Clinical practice guidelines, developed through systematic review of the medical literature and considering the best available evidence, provide guidance for common clinical scenarios. However, in the clinical setting, patients often present with characteristics and nuances that may fall outside the realm of available evidence and guidelines, and hence, shared decision-making will be essential in the evaluation and management of these patients. The challenges in the diagnosis of VWD are mainly attributable to the heterogeneity of the disorder, limitations of laboratory assays, and the significant impact of various physiologic processes on von Willebrand factor. The impact of physiologic normalization of von Willebrand factor, which may occur in various settings such as pregnancy, inflammation, or aging, remains uncertain, as is the optimal management in these scenarios. Multidisciplinary and individualized care, based on evolving evidence supported by clinicians, patients, caregivers, and stakeholders, will be needed to ensure the highest quality care for those who live with VWD.

The diagnosis, natural history, and management of von Willebrand disease in women in the age of guidelines

INTRODUCTION

Women and girls with bleeding disorders face multiple bleeding challenges throughout their life. The most significant morbidity and mortality are due to heavy menstrual bleeding and postpartum hemorrhage in their reproductive years. The ASH/ISTH/NHF/WFH 2021 guidelines on diagnosing and managing von Willebrand disease (VWD) provide several new updates.

AREAS COVERED

Women with VWD have a higher prevalence of heavy menstrual bleeding. The subpopulation of adolescents is particularly vulnerable, as the diagnosis is often delayed with increased comorbidity of iron deficiency anemia and associated symptoms. A detailed review is done on the prevalence of bleeding-related complications, especially heavy menstrual bleeding (HMB) and post-partum hemorrhage (PPH). The management strategies are also reviewed in detail, with a specific focus on the target factor levels and the use of antifibrinolytics.

EXPERT OPINION

The 2021 ASH/ISTH/NHF/WFH diagnostic and management recommendations are reviewed with a specific focus on hormonal methods of HMB management and antifibrinolytics in this situation. The reviewed topics include neuraxial anesthesia, factor cutoff, and tranexamic acid use in the postpartum period.

Thrombocytopenia in pregnancy

Hematologists are often consulted for thrombocytopenia in pregnancy, especially when there is a concern for a non-pregnancy-specific etiology or an insufficient platelet count for the hemostatic challenges of delivery. The severity of thrombocytopenia and trimester of onset can help guide the differential diagnosis. Hematologists need to be aware of the typical signs of preeclampsia with severe features and other hypertensive disorders of pregnancy to help distinguish these conditions, which typically resolve with delivery, from other thrombotic microangiopathies (TMAs) (eg, thrombotic thrombocytopenic purpura or complement-mediated TMA). Patients with chronic thrombocytopenic conditions, such as immune thrombocytopenia, should receive counseling on the safety and efficacy of various medications during pregnancy. The management of pregnant patients with chronic immune thrombocytopenia who are refractory to first-line treatments is an area that warrants further research. This review uses a case-based approach to discuss recent updates in diagnosing and managing thrombocytopenia in pregnancy.

The VWF binding aptamer rondoraptivon pegol increases platelet counts and VWF/FVIII in type 2B von Willebrand disease

Type 2B von Willebrand disease (VWD) is characterized by an increased binding affinity of von Willebrand factor (VWF) to platelet glycoprotein Ib. This can lead to clearance of high-molecular-weight (HMW) multimers and thrombocytopenia with a resulting moderate-severe bleeding phenotype. Rondoraptivon pegol (BT200) is a pegylated aptamer binding to the A1 domain of VWF with a novel mechanism of action: it enhances VWF/factor VIII (FVIII) levels by decreasing their clearance. To study the potential benefit of rondoraptivon pegol in patients with type 2B VWD, we conducted a prospective phase 2 trial. Patients with type 2B VWD received 3 mg rondoraptivon pegol subcutaneously on study days 1, 4, and 7, followed by 6 to 9 mg every week until day 28. Five patients (male:female ratio = 3:2) were included. Rondoraptivon pegol rapidly tripled platelet counts from a median of 60 to 179 × 10E9/L (P < .001). Circulating VWF antigen increased from a median of 64% to 143%, which doubled FVIII activity levels from 67% to 134%. In all thrombocytopenic patients, plasma levels of VWF:GPIbM normalized, VWF ristocetin cofactor and VWF collagen-binding activity increased, and HMW multimers appeared. These pronounced improvements reversed during washout of the drug, thus demonstrating causality. The A1 domain binding aptamer directly corrects the underlying defect of type 2B VWD, thus providing a novel potential option for prophylaxis and treatment of patients with this VWD type. These data provide the basis for a phase 2b/3 trial in such patients. This trial was registered at www.clinicaltrials.gov as #NCT04677803.

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

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

Postpartum Hemorrhage in Patients with Type 1 von Willebrand Disease: A Systematic Review

Type 1 von Willebrand disease (VWD) is the most common subtype of VWD, comprising 75% of VWD patients. We provide a systematic review of type 1 VWD in pregnancy. Our objective was to evaluate the rate of postpartum hemorrhage (PPH) in patients with known type 1 VWD. The primary outcome was rate of PPH. Primary PPH was defined as a cumulative blood loss ≥1,000 mL, or blood loss accompanied by signs and symptoms of hypovolemia within 24 hours postpartum or requiring blood products. Secondary PPH was defined as significant bleeding 24 hours to 12 weeks postpartum. Relevant articles published in English pertaining to VWD and pregnancy were identified without any time or study limitations. Seven articles (n = 144 pregnancies) met inclusion criteria. The rate of primary PPH was 4/144 (2.8%). The secondary PPH rate was reported in four studies, and occurred in 7/48 pregnancies (14.6%), ranging from 2 to 19 days postpartum. In conclusion, according to this systematic review, the frequency of primary PPH in pregnancies with known type 1 VWD is 2.8%. This is similar to the overall PPH rates of 3% reported in the literature. Although the sample size was small, secondary PPH occurred in almost 15% of pregnancies, while in the overall obstetrical population this occurs in approximately 1% of cases. Patients with known type 1 VWD may not be at increased risk of primary PPH, though they appear to bear increased risk of secondary PPH.