VWF and von Willebrand disease (hereditary or acquired): Von Willebrand disease (VWD) is a common autosomal inherited bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (VWF), a multi-adhesive protein which binds platelets to exposed subendothelium and carries factor VIII (FVIII) in circulation.1,2 As a consequence, FVIII, the protein deficient in hemophilia A, may be variably reduced.