The incidence of von Willebrand disease in the Netherlands is unknown, but the occurrence of all types of von Willebrand disease together is estimated at 1:100-1:200 individuals. Most patients have mild von Willebrand disease, mostly type 1. For the more severe forms of von Willebrand disease the incidence in unclear, but the expectation is, that there are at least 500-1500 patients. In the Netherlands, an unique situation exists for the treatment of patients with hemophilia and related coagulation disorders. In 2000 a hemophilia management policy was set up by the Ministry of Health, which stated that the care for these patients should be concentrated in 13 Hemophilia Treatment Centers (HTC). The representatives of the attending centers, the hemophilia specialists, are organized in the NVHB, the Dutch society of Hemophilia treaters. In the hemophilia management policy is stated that all patients with a coagulation disorder dependent of replacement products must be treated in a HTC or under responsibility of a HTC. These patients are seen in a HTC at least once a year.~Because all moderate and severe von Willebrand patients in the Netherlands are known in HTC, it is possible to register and study this population. This is imperative to the research of von Willebrand disease. Because the moderate and severe forms of von Willebrand disease are rare, it is impossible for an individual center to perform research of moderate severe and severe von Willebrand disease. Therefore a national approach is necessary.~For optimal care of patients with the moderate and severe form of von Willebrand disease a better understanding of symptoms, diagnostics, treatment and complications of treatment is necessary. The present study aims to register and investigate all patients in the Netherlands with moderate and severe von Willebrand disease to gain understanding of the clinical presentation, the treatment and the complications of treatment in moderate and severe von Willebrand disease. Another goal is to investigate the influence of von Willebrand disease on quality of life.~To answer these questions a questionnaire is developed, which will be sent to the study population. In addition, blood will be drawn for von Willebrand factor measurement and plasma and DNA will be stored. The relationship between laboratory parameters, (including von Willebrand factor, FVIII and prothrombotic coagulation disorders) and the clinical phenotype in patients with moderate and severe von Willebrand disease will be studied. We will assess the effect of the laboratory parameters on both the severity of bleeding tendency, and the possible protecting effect on the risk of arterial thrombosis. In the future mutation analysis of the VWF gene will be performed in patients with moderate and severe von Willebrand disease in the Netherlands.
The objective of this study is to assess the clinical presentation, the treatment and the complications of the disease and treatment in moderate and severe von Willebrand disease. Another goal is to investigate the influence of von Willebrand disease on quality of life.