Australian Dental Council (ADC) Practice Test

In patients with Von Willebrand's disease, the most notable clinical sign is a prolonged bleeding time. Von Willebrand's disease is a bleeding disorder caused by a deficiency or dysfunction of von Willebrand factor (vWF), which plays a critical role in platelet adhesion and aggregation during clot formation. When there is inadequate vWF, platelets cannot effectively adhere to the site of injury, leading to a longer duration of bleeding.

This disorder does not typically cause high platelet counts or elevated factor IX levels; in fact, the levels of factor VIII can also be affected since vWF serves as a stabilizing factor for factor VIII in circulation. Normal factor VIII levels would be misleading in the context of a functional deficiency of vWF because the presence of vWF is essential for the proper function of factor VIII during clotting. Hence, the hallmark clinical manifestation of bleeding in these patients, as a reflection of their impaired hemostasis, is observed as a prolonged bleeding time.