F8 and hemophilia A: Further investigations revealed an antigenic WILLEBRAND factor at 344%, a WILLEBRAND factor activity at 182%, a factor VIII at 1% (normal between 60 and 150%) and an anti-factor VIII (anti-FVIII) antibody at 665 Bethesda units (BU)/ml (normal less than 0.6 BU/ml), confirming the diagnosis of acquired hemophilia A.