Chapter 135 - Laboratory Diagnosis of Acquired von Willebrand’s Syndrome

Abstract

Acquired von Willebrand syndrome (AVWS) is a rare disorder in which laboratory findings and clinical symptoms mimic various types of von Willebrand disease (VWD). It may be suspected in a patient with abnormal VWD tests and no previous history of excessive bleeding, who has one of the number of disorders and conditions known to predispose to AVWS. AVWS may be due to the presence of an autoantibody, adsorption of von Willebrand factor (VWF) by cells or surfaces, increased proteolysis, or decreased or aberrant production. The diagnosis of AVWS uses the assays described for inherited VWD, with ristocetin cofactor the most sensitive test. More than 80% of AVWS cases show loss of high-molecular-weight VWF multimers. Inhibitory autoantibodies directed against VWF are detected in fewer than 20% of cases.