Von Willebrand's Disease Type B: A Newly Defined Bleeding Diathesis

Summary: A patient with a lifelong bleeding diathesis is described. Studies of haemostatic function revealed a prolonged bleeding time and reduced glass bead adhesiveness. All other routine studies of haemostatic function yielded normal results, in particular the Factor VIII level, estimated both by antibody and coagulation techniques. Ristocetininduced platelet aggregation was absent and could be corrected by the addition of plasma or serum from normal controls or haemophiliacs, but not from patients with Von Willebrand's disease. It is apparent that the Von Willebrand plasma factor is either reduced in amount or inactive in this patient without an accompanying reduction in the Factor VIII level. It is postulated that Factor VIII may have two separate sites of biological activity, one concerned with the intrinsic pathway of coagulation and the other with platelet glass bead adhesiveness and skin bleeding time. It is proposed that this patient possesses a specific abnormality in the latter site, in contradistinction to the specific defect in the site concerned with intrinsic coagulant function in haemophilia.