Von Willebrand Disease - Pathophysiology

Pathophysiology

vWF is mainly active in conditions of high blood flow and shear stress. Deficiency of vWF therefore shows primarily in organs with extensive small vessels, such as the skin, the gastrointestinal tract and the uterus. In angiodysplasia, a form of telangiectasia of the colon, shear stress is much higher than in average capillaries, and the risk of bleeding is increased concomitantly.

In more severe cases of type 1 vWD, genetic changes are common within the vWF gene and are highly penetrant. In milder cases of type 1 vWD there may be a complex spectrum of molecular pathology in addition to polymorphisms of the vWF gene alone. The individual's ABO blood group can influence presentation and pathology of vWD. Those individuals with blood group O have a lower mean level than individuals with other blood groups. Unless ABO group–specific vWF:antigen reference ranges are used, normal group O individuals can be diagnosed as type I vWD, and some individuals of blood group AB with a genetic defect of vWF may have the diagnosis overlooked because vWF levels are elevated due to blood group.