Landscape and Spectrum of VWF Variants in Type 2 Von Willebrand Disease: Insights from a German Patient Cohort

von Willebrand disease (VWD) type 2 arises from variants in von Willebrand factor (VWF) that disrupt its essential hemostatic functions. As per ISTH guidelines, it is classified as type 2A, 2B, 2M, and 2N based on the affected VWF roles.This population-based study aims to uncover the genotype and laboratory phenotypes in type 2 VWD, providing insights into underlying genetics and genotype-phenotype associations.Our cohort included 247 patients from 196 families. Patients were characterized through multiple VWF phenotypic assays and genetic analyses, including DNA sequencing, copy number variation evaluations, and bioinformatic assessments.A total of 86 index patients (IPs, 44%) were diagnosed with type 2A, the most prevalent subtype. Additionally, 27 IPs (14%) were diagnosed with type 2N, 24 IPs (12%) with type 2B, 17 IPs (9%) with type 2M, and 42 IPs categorized as type U VWD carried VWD-associated variants but could not be assigned to a specific subtype. VWF variants were detected in 187 out of 196 (95%) individuals. A total of 222 VWF variants were identified: 187 missense (84%), 22 null alleles (10%), 5 regulatory (2%), 6 gene conversions (3%), and 2 silent variants (1%). Many variants were recurrent in our cohort, resulting in 114 distinct variants. Of these, 45 (39%) were novel.Our data expands the spectrum of disease-associated variants in VWF, including many newly identified variants. This provides valuable insights for accurate diagnosis and personalized treatment. Additionally, the significant genetic heterogeneity among type 2 patients highlights the challenges in sub-classification.