From the Guidelines
Von Willebrand factor is a blood clotting protein that plays a crucial role in the blood clotting process by helping platelets stick to damaged blood vessels and to each other, and it also carries and protects Factor VIII in the bloodstream. This protein is essential for preventing excessive bleeding, and its deficiency or defect can lead to Von Willebrand disease, the most common inherited bleeding disorder [ 1 ]. The symptoms of Von Willebrand disease can range from mild bleeding to severe, life-threatening bleeding, and can include easy bruising, nosebleeds, heavy menstrual periods, and prolonged bleeding after injury or surgery [ 1 ].
Key Functions of Von Willebrand Factor
- Mediates platelet adhesion and aggregation at sites of vascular injury
- Carries and stabilizes blood coagulation factor VIII (FVIII) in the circulation [ 1 ]
- Produced by endothelial cells lining blood vessels and by megakaryocytes in the bone marrow
- Circulates in the blood in various sizes, with larger multimers being more effective at promoting clot formation
Diagnosis and Treatment
Diagnosis of Von Willebrand disease involves blood tests measuring the amount, function, and structure of Von Willebrand factor [ 1 ]. Treatment may include desmopressin (DDAVP) to stimulate release of stored Von Willebrand factor, which has been shown to be effective in patients with acquired or inherited vWF deficiency [ 1 ], or replacement therapy with concentrates containing the factor. Desmopressin, in a dose of 0.3 μg.kg-1, may be considered in patients presenting for surgery with acquired or inherited vWF deficiency [ 1 ]. However, the use of desmopressin has been evaluated in the peri-operative setting, and while it may lead to a small reduction in blood loss and volume of RBCs transfused, the differences are unlikely to be of clinical importance [ 1 ].
From the Research
Definition and Cause of Von Willebrand Disease
- Von Willebrand disease is a common inherited bleeding disorder characterized by excessive mucocutaneous bleeding 2.
- The disease is caused by quantitative and/or qualitative defects of the von Willebrand factor (VWF), a multimeric high molecular weight glycoprotein 3.
- VWF promotes its function in two ways: by initiating platelet adhesion to the injured vessel wall under conditions of high shear forces, and by its carrier function for factor VIII in plasma 3.
Types of Von Willebrand Disease
- There are three main types of von Willebrand disease: type 1, type 2, and type 3 4, 2.
- Type 1 and type 3 represent quantitative variants, while type 2 is a group of qualitative variants 2.
- Type 2 is further divided into four subtypes: type 2A, type 2B, type 2M, and type 2N, each with distinct characteristics 2.
Role of Von Willebrand Factor
- VWF plays a crucial role in primary hemostasis by binding platelets to exposed subendothelium and carrying factor VIII in circulation 4.
- The deficiency or abnormal activity of VWF is responsible for von Willebrand disease 4.
- VWF stabilizes factor VIII in circulation, and its deficiency can lead to reduced factor VIII levels 4, 3.
Treatment of Von Willebrand Disease
- Desmopressin is a common treatment for von Willebrand disease, particularly for type 1 patients 4, 5, 3.
- Desmopressin can transiently correct the deficiency of factor VIII and VWF for up to 8-12 hours in patients with type 1 von Willebrand disease and factor VIII and VWF levels ≥10 U/dL 4.
- Von Willebrand factor-containing concentrates, with or without factor VIII, may be used when desmopressin is not effective or when correction is required for an extended period 4, 6.