Two Cases of von Willebrand’s Disease with Specific Inhibitors of Ristocetin Induced Aggregation of Normal Platelets

Abstract

Ten patients (8 females and 2 males) with severe form of von Willebrand’s disease were investigated for the occurrence of inhibitors blocking Ristocetin induced aggregation of normal platelets. All these patients had been multiply transfused and had the classical signs of von Willebrand’s disease, prolonged bleeding time, less than 10% of normal factor VIII activity and correspondingly low factor VIII antigen levels, normal ADP induced platelet aggregation but no Ristocetin induced aggregation. In none of these patients circulating anticoagulants neutralizing factor VIII activity had been demonstrated. Plasma samples from 2 of these patients were found to block Ristocetin induced platelet aggregation of normal plasma. In one of these patients the inhibitor was found to be of IgG type. This patient otherwise had a normal serum electrophoretic pattern. The inhibitor of the other patient is being investigated.