Letter: Experimental model for von Willebrand's disease.

Abstract

IT has been reported1 that Ristocetin induces aggregation of platelets in normal platelet-rich plasma (PRP) but not of platelets from patients with von Willebrand's disease. Results presented here demonstrate that the aggregation of platelets induced by Ristocetin involves a factor present in normal and haemophilia A plasma and absent in Willebrand plasma. Lack of such a factor would then explain the inability of platelets to aggregate in response to Ristocetin in von Wille-brand's disease. In eight patients fulfilling the criteria of von Willebrand's disease (Table 1), platelet aggregation induced by Ristocetin was markedly deficient when compared to healthy normal plasmas or did not occur at all. The abnormal responses of platelets from von Willebrand's patients could be corrected by the addition of small volumes of normal platelet-poor plasma (PPP) (Fig. 1); similar correction was achieved by Haemophilia A PPP but not by PPP from patients with von Willebrand's disease.