Clinical meaning
Von Willebrand disease (VWD) is the most common inherited bleeding disorder, affecting approximately 1% of the general population (though clinically significant disease is less prevalent). It is caused by quantitative or qualitative deficiency of von Willebrand factor (VWF), a large multimeric glycoprotein that plays two essential roles in hemostasis: platelet adhesion and coagulation factor VIII protection. Under normal hemostatic conditions, when a blood vessel is injured, subendothelial collagen is exposed. VWF is released from Weibel-Palade bodies in endothelial cells and alpha-granules in platelets. The released VWF binds to exposed collagen and undergoes conformational change under the shear stress of flowing blood, exposing binding sites for the platelet glycoprotein Ib/IX/V (GPIb) receptor. This VWF bridge between collagen and platelets is the primary mechanism for platelet adhesion at sites of vascular injury, especially in areas of high shear stress such as arteries and the microvasculature. Without adequate VWF, platelets cannot adhere properly to the injured vessel wall, resulting in impaired primary hemostasis. VWF also serves as a carrier protein for coagulation factor VIII, protecting it from premature degradation by activated protein C and other proteases in the circulation. Factor VIII has a half-life of approximately 12 hours when bound to VWF but only 2 hours when circulating free. Therefore, VWF deficiency leads to secondary factor VIII deficiency, which can impair the intrinsic coagulation cascade and prolong the activated partial thromboplastin time (aPTT). VWD is classified into three types based on the nature of the VWF defect. Type 1 (70-80% of cases) is a partial quantitative deficiency with VWF levels reduced to 20-50% of normal; inheritance is autosomal dominant; symptoms are usually mild with mucocutaneous bleeding. Type 2 (15-20% of cases) involves qualitative defects in VWF function; subdivided into 2A (decreased platelet-dependent function with loss of high-molecular-weight multimers), 2B (increased binding affinity for platelet GPIb causing spontaneous platelet aggregation and thrombocytopenia), 2M (decreased platelet binding without loss of multimers), and 2N (decreased binding to factor VIII, mimicking hemophilia A). Type 3 (less than 5% of cases) is the most severe form with virtually complete absence of VWF; inheritance is autosomal recessive; presents with both mucocutaneous bleeding and joint/soft tissue bleeding similar to severe hemophilia. The clinical hallmark of VWD is mucocutaneous bleeding: prolonged nosebleeds (epistaxis), heavy menstrual bleeding (menorrhagia), easy bruising, prolonged bleeding from cuts and dental procedures, and gastrointestinal bleeding. Unlike hemophilia, joint bleeding (hemarthrosis) is uncommon except in severe Type 3 disease. Menorrhagia is often the presenting symptom in females and may lead to iron-deficiency anemia. VWD is diagnosed through a combination of VWF antigen level (quantitative), VWF ristocetin cofactor activity (functional), factor VIII activity, and VWF multimer analysis. The bleeding time is prolonged, and the aPTT may be prolonged (due to secondary factor VIII deficiency) or normal (if factor VIII levels remain adequate). For the practical nurse, care focuses on bleeding precautions, gentle handling, medication administration (desmopressin and VWF concentrates), patient education about avoiding antiplatelet medications, and ensuring the patient carries medical identification indicating their bleeding disorder.