Type 2N VWD: Conclusions from the Spanish PCM-EVW-ES project

INTRODUCTION

Type 2N von Willebrand disease (VWD) is characterized by a decreased affinity of von Willebrand factor (VWF) for factor VIII (FVIII). Abnormal binding of FVIII to VWF (VWF:FVIIIB), results in low FVIII plasma levels, which can lead to a misdiagnosis of mild haemophilia A. Accurate diagnosis of type 2N VWD is essential for appropriate genetic counselling and therapy. This disease can be distinguished from haemophilia A by in vitro assays (measurement VWF:FVIIIB activity) and/or genetic analysis.

AIM

To identify the current challenges in the diagnosis and treatment of this type of VWD and provide an in-depth description of the phenotypes and mutations identified.

RESULTS

Twenty-eight patients had at least one type 2N mutation, and 13 of these had a type 2N mutation combined with other variations. Three type 2N mutations were detected: p.Arg816Trp, p.Arg854Gln, and p.Arg763Ser. Two of these are the most frequently described mutations worldwide. This mutational spectrum differs from the broad spectrum seen in neighbouring France, where at least eight distinct 2N mutations have been found. In the PCM-EVW-ES cohort, 11 asymptomatic type 2N carriers with borderline FVIII plasma levels would probably have been excluded if the evaluation had been based on clinical and laboratory data only. Likewise, three patients with a severe phenotype would have been classified as homozygous for a 2N mutation if only the phenotype study had been performed.

CONCLUSION

The high detection yield and affordability of next-generation sequencing support the use of this technology as a first-line diagnostic tool in this setting.

Co-inheritance of mild hemophilia A and heterozygosity for type 2N von Willebrand disease: a diagnostic and therapeutic challenge

Hemophilia A and von Willebrand disease are the two most common inherited bleeding disorders. Despite their frequency, however, there are very few reports of co-inheritance of the two disorders. We present the first report of a patient with mild hemophilia A and heterozygosity for type 2N von Willebrand disease (VWD). We discuss the patient's phenotype and highlight the diagnostic and therapeutic challenges caused by this co-inheritance.