Diagnosing von Willebrand disease: genetic analysis

Abstract

Investigation of a patient with possible von Willebrand disease includes a range of phenotypic analyses. Often, this is sufficient to discern disease type, and this will suggest relevant treatment. However, for some patients, phenotypic analysis does not sufficiently explain the patient’s disorder and for this group, genetic analysis can aid diagnosis of disease type. PCR and Sanger sequencing have been mainstays of genetic analysis for several years. More recently, next generation sequencing has become available, with the advantage that several genes can be simultaneously analysed where necessary, e.g. for discrimination of possible type 2N von Willebrand disease or mild haemophilia A. Additionally, several techniques can now identify deletions/duplications of an exon or more that result in von Willebrand disease including multiplex ligation-dependent probe amplification and micro-array analysis. Algorithms based on next generation sequencing data can also identify missing or duplicated regions. These newer techniques enable causative VWF defects to be identified in more patients than previously, aiding a specific VWD diagnosis. Genetic analysis can also be helpful in the discrimination between type 2B and platelet-type von Willebrand disease and in prenatal diagnosis for families with type 3.

Genetic Background of von Willebrand Disease: History, Current State, and Future Perspectives

“…Most identified mutations are heterozygous missense mutations, small deletions/insertions, and splicing and nonsense mutations in coding region, promoter, and splicing sites. 15,31 Mutational Spectrum of von Willebrand Disease…”

“…Mutations affecting binding to collagen types I/III, and also, to a lesser extent, type IV (p.Arg1315Cys, p.Ser1358Asn, p.Gln1402Pro, p.Arg1392_Gln1402del, p.Ile1425Phe, and p.Arg1399His) and type VI (p.Ser1387Ile, p.Gln1402Pro) are located in the A1 or A3 domains. 31,52,53 The Arg1399His mutation affecting binding to collagen types IV and VI has also been identified among healthy controls. Although it cannot be regarded as a definite VWD-causing mutation, it may be associated with an increased risk for bleeding.…”

“…23,35 The most frequent type 2N mutations are p.Arg816Trp and in the European population p.Arg854Gln, for which approximately 1% of individuals are heterozygous. 31 These mutations also affect patient's response to DDAVP; for example, patients with p.Arg816Trp mutation had FVIII levels below 0.1 IU/dL and FVIII levels do not respond to DDAVP. 35…”

How I treat type 2B von Willebrand disease

“…Alternately, the diagnosis of type 2B VWD can be made through genetic testing. 24,25 Genetic testing can be diagnostic for type 2 VWD 25 because multiple known causative DNA variants have been reported in the VWF A1 domain ( Figure 2). 26 Notably, platelet function analyzer 100 (PFA-100) closure times were not informative in this case.…”

Update on Molecular Testing in von Willebrand Disease

“…In addition, phenotypic testing that measures plasma VWF levels has shortcomings in that VWF levels may vary due to other underlying illnesses or stress often making interpretation difficult; these factors do not influence genetic testing. 2,70 However, despite the possible advantages of genetic testing, its routine use for the analysis of VWF in VWD is still a matter of controversy. In this regard, there are several pros and cons to be considered.…”