A spayed female mixed-breed dog was presented with excessive bleeding from a wound in the mouth. The dog had a history of self-limiting bleeding following ovariohysterectomy. A coagulation test revealed prolongation of the activated partial thromboplastin time (20.2 seconds; reference interval: 11.0-15.0 seconds), prothrombin time was normal and factor VIII activity was markedly decreased (1.9%; reference interval: >50%). The von Willebrand factor antigen concentration was 158% (reference interval: >50%). A cross-mixing test indicated that the diminished factor VIII activity was due to deficiency or dysfunction of factor VIII rather than inhibition of factor VIII activity. Based on these results, the dog was diagnosed with haemophilia A. Haemophilia A should be considered in the differential diagnosis of bleeding disorders also in female mixed-breeds dogs.
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