von Willebrand's disease

von Willebrand's disease (vWd) is the most frequent inherited bleeding disorder in people and in dogs, but has also been described in other species (pig, rabbit, horse, cow and cat). Patients affected by von Willebrand's disease have a reduced quantity of functional von Willebrand factor (vWf). This deficiency produces impaired platelet adhesion to exposed sub-endothelium and subsequent platelet aggregation. The coagulation factor VIII (FVIII) circulates bound to vWf in plasma. The half-life of this factor is shorter without vWf. Clinical signs vary with severity of disease (in terms of vWf status), type of vWd, genotype, and concurrent diseases. Definitive diagnosis of vWd requires specific determination of plasma vWf concentration (with a result lower than 49 canine units (CU)/dl compared to the reference pool considered to be 100 CU/ dl). Transfusion therapy, specifically cryoprecipitate (cryo) as vWf is concentrated in this blood product, is the treatment of choice in vWd in the dog. The advantage of cryo is the low volume needed to infuse a large quantity of vWf (1 unit/10 kg body weight as needed). If cryo is not available, fresh frozen plasma is indicated (6-10 ml/kg body weight bid or tid) or fresh whole blood (12-25 ml/kg/day) especially if marked haemorrhage has occurred. © 1997 Springer-Verlag London Limited.