Thrombopathies causing bleeding in a boxer and mixed-breed dog

Hereditary platelet function disorders are clinically characterized by recu rrent surface bleeding and prolonged bleeding time, despite normal platelet count and coagulation tests. The authors describe persistent thrombopathie s in two young dogs with increased bleeding tendencies but with normal plas ma coagulation times and von Willebrand factor (vWf) concentrations. Buccal mucosal bleeding times were prolonged in both dogs. In aggregation studies , platelets underwent only a shape change or minimal aggregation in respons e to adenosine diphosphate and collagen. Whole-platelet adenine nucleotide concentrations were normal. Electron microscopic evaluation of fibrinogen a nd vWf binding to the platelets of case no. 1 demonstrated the presence of glycoprotein Ilb/llla and Ib receptors. Thus, the intrinsic platelet functi on defects may be different in these two dogs and may likely represent secr etion/signal transduction disorders.