Acquired von Willebrand syndrome (AvWS) is a relatively rare acquired bleeding disorder similar to inherited von Willebrand disease in terms of laboratory findings, and occurs without a personal or family history of bleeding. A 23-year-old man with no previous disease history and no family history of hemorrhagic diathesis was referred to our hospital because of recurrent epistaxis and intramuscular hematoma. He was diagnosed as having AvWS because of an almost complete absence of ristocetin cofactor activity (vWF：RCo) despite normal vWF antigen level. Furthermore, anti-vWF antibody was detected in his serum using home-brewed ELISA. Finally, the amyloid deposit was found in muscle biopsy. He was diagnosed with AvWS which is associated with amyloidosis. AvWS should be considered in patients with current bleeding diatheses and no past history of bleeding. (Korean J Hematol 2009;44:310-314.)

Keywords: von Willebrand disease, Autoantibodies, Amyloidosis