Pathophysiology of acquired von Willebrand syndrome (avWS). von Willebrand factor (vWF) is synthesized by the endothelial cell lining of blood vessels. It is released into the circulation as multimers of varying size (schematic shows a multimer of 5 subunits released by the endothelium). Mechanisms of avWS include: 1) reduced synthesis of vWF in the setting of hypothyroidism (and certain medications), 2) antibody-mediated inhibition or clearance of vWF, 3) increased absorption of vWF multimers onto the surface of activated platelets, and 4) shear-stress-mediated cleavage/proteolysis of vWF multimers.
