Genetic background of von Willebrand disease

Introduction Von Willebrand disease (VWD) is an autosomal hereditary bleeding disorder and in rare situation is also acquired. Its prevalence in the population is very high with about 1 %. There are known quantitative deficiencies (type 1 and type 3) and qualitative deficiencies (type 2). The type 2 VWD contains several possible subtypes, which are often difficult to diagnose with common laboratory methods. The von Willebrand gene consists of 52 exons and is spans about 180 kb of the genome. Our aim was to analyse the molecular defect underlying VWD in a cohort of 72 patients in order to facilitate the classification of the disease.

Method In 72 patients, VWF gene was analysed by Sanger Sequencing. In cases without mutation, MLPA (Multiplex Ligation dependent Probe Amplification) was performed to detect large deletions or duplications. The characterisation of the variants was performed with in silico evaluation tools, including Polyhen-2, SIFT, Panther and Pmut.

Results We detected 30 different mutations in the VWF gene. Therefrom, 27 variants were previously described in the Human Genome Mutation database (HGMD) as disease causing mutations. Of these, we identified 23 Missense Mutations, one nonsense-mutation, one frameshift mutation (small deletion) and one splice-site mutation. The most frequent phenotype described for the known mutations was type 1, followed by type 2A and 2B. Two mutations were causative for type 2 N and two mutations for type 2M. Three mutations causative for VWD type 3 were identified. The type 3 mutations were one splice-site mutation, one frameshift mutation (small deletion) and one large deletion of the whole VWF gene. Three variants were novel and not described in the Polymorphism databank of the National Center for Biotechnology Information (dbSNP, NCBI) as Polymorphism. The novel variants were all missense mutations and further analysed to classify the potential impact for disease. The three novel mutations were predicted as potential missense mutations with pathogenic effect. Further functional analysis and phenotype studies will be necessary to determine the type of VWD caused by this mutations.

Conclusion Genetic anlaysis of the VWF gene can help to identify the subtype of VWD by providing insight in the localisation of the mutation in certain domains of the protein or by identifiying already known mutations. In silico methods are useful tools to predict the effect of novel genetic variants on the protein function or structure of the VWF. Nevertheless, these methods cannot replace in vitro analysis by laboratory experiments and common diagnostic tests, multimer analysis, phenotypic studies of patients and co-segregation analysis within families to classify the type of VWD.

Publication History

Article published online:
20 February 2023