Objective: To characterize the biochemical and genetic basis of a clinically severe form of von Willebrand's disease (vWD) in German Wirehaired Pointers.
Design: Case series.
Sample population: Plasma samples from 335 German Wirehaired Pointers (8 clinically affected).
Procedure: Plasma samples were evaluated, using an ELISA, to determine von Willebrand factor (vWF) antigen concentration. Additional studies performed on samples from clinically affected dogs included coagulation screening tests, factor VIII coagulant activity assays, and immunoelectrophoresis to determine vWF multimeric composition.
Results: Mucosal bleeding and bleeding at sites of cutaneous injury were observed in affected dogs by 6 months old. Plasma vWF antigen concentration was markedly reduced, and there was a lack of high molecular weight vWF multimers; findings compatible with type-II vWD. Inheritance and expression pattern of vWD in this breed was most compatible with that of an autosomal recessive trait.
Clinical implications: Von Willebrand's disease should be included in the differential diagnoses of bleeding diatheses in German Wirehaired Pointers, with definitive diagnosis confirmed on the basis of canine-specific vWF assays.