Decreased adhesion of giant (Bernard-Soulier) platelets to subendothelium. Further implications on the role of the von Willebrand factor in hemostasis

The platelets of two patients with the Bernard-Souller (giant platelet) syndrome were not aggregated by bovine factor VIII. Platelet aggregation by rlstocetin was also absent and, in contrast to the findings in von Willebrand's disease, this defect was not corrected by human factor VIII. The platelets of patients with the Bernard-Soulier syndrome may lack a receptor for the von Willebrand factor activity of factor VIII (VIII_VWF), whereas the abnormal platelet function in von Willebrand's disease is due to a decreased level of VIII_VWF in their plasma. As in the latter disorder, the adhesion of platelets to subendothellum was impalred in the two patients with the Bernard-Souller syndrome that we studied. These findings provide further evidence that VIII_VWF, through its effect on platelets, plays an important role during the primary arrest of bleeding.