Reduced Plasma von Willebrand Factor Fragments in Patients with Various Types of von Willebrand Disease

We previously reported a new analytical immunoblotting method to detect reduced plasma von Willebrand factor (vWF) fragments using polyclonal anti-reduced vWF antibody and demonstrated that the reduced normal plasma vWF consists of at least five or six fragments, 240kDa for the main fragment and 216 (220, 210), 194, 164 and 144kDa for minor fragments. In this study, we describe the reduced fragments in patients with various types of von Willebrand disease (vWD) (type I: 7 patients, type IIA: 4 patients and type IIB: 3 patients) using this method. Of seven patients with type I vWD, one patient with an equally low level of ristocetin cofactor activity (vWF: RCo) and vWF antigen (vWF: Ag) showed normal relative proportions of each fragment. However, three of four patients with a low level of vWF: RCo compared to vWF: Ag showed a relatively increased proportion of the 164kDa fragment. The remaining two patients demonstrated a new 200kDa reduced fragment in addition to those of normal plasma vWF. In type II A vWD, all patients showed a relatively increased proportion of the 164kDa fragment. In type IIB vWD, two of three patients also showed a relatively increased proportion of the 164kDa fragment. These results suggest that plasma vWF with a low vWF: RCo compared with the vWF: Ag ratio tends to show an increased proportion of the 164kDa reduced fragment, even in type I vWD with a normal multimeric structure. Fragment analysis of reduced vWF in patients with vWD is useful to understand the abnormality at the molecular level, especially in type I vWD.