Advances in the diagnosis and management of type 1 von Willebrand disease

Von Willebrand disease (VWD) is an autosomally inherited bleeding disorder caused by a deficiency and/or abnormality of von Willebrand factor (VWF). VWF is a multimeric adhesive protein that plays an important role in primary hemostasis by promoting platelet adhesion to the subendothelium at sites of vascular injury and platelet-platelet interactions at high-shear rate conditions. Furthermore, VWF is the carrier of factor VIII, thus indirectly contributing to the coagulation process. Most cases have a partial quantitative deficiency of VWF (type 1 VWD) with variable bleeding tendency, whereas qualitative variants (type 2 VWD), due to a dysfunctional VWF, are clinically more homogeneous and account for approximately 20-30% of cases. Type 3 VWD is rare and these patients have moderate-to-severe bleeding diathesis, display a recessive pattern of inheritance and virtual absence of VWF. The diagnosis of VWD may be difficult, especially in type 1 disease, since the laboratory phenotype of the disorder is very heterogeneous and confounded by the influence on VWF levels by factors outside the VWF gene (e.g., blood group). An array of tests are usually required to characterize the several types of the disorder in order to predict the best treatment modality. Desmopressin is the treatment of choice for most patients with type 1 VWD because it corrects the the dual defects of hemostasis, that is, abnormal coagulation expressed by low levels of factor VIII and abnormal platelet adhesion expressed by the reduction of VWF.