In vitro abnormality of the blood in von Willebrand's disease correctable by normal plasma.

VON WILLEBRAND'S disease is a familial haemorrhagic disorder affecting both sexes and characterized by a prolonged bleeding time and a low level of antihaemophilic factor (AHF, factor VIII). The prolonged bleeding time is associated with abnormal in vivo platelet adhesiveness1. However, no in vitro abnormality has been detected in the factors believed to be essential for haemostasis, such as platelet viscous metamorphosis2 and aggregation of platelets by adenosine diphosphate (unpublished observation) and by collagen3. The platelet-aggregating ability of the patient's connective tissue is also unimpaired3. Recent reports have indicated that the abnormal bleeding time can be corrected by transfusion of fresh plasma or a plasma fraction4–6. This effect can only be tested in patients. Identification of an in vitro abnormality in von Willebrand's disease would facilitate purification of this plasma factor; it would also help to elucidate both the pathological physiology of the disease and the normal physiology of haemostasis.