[Hemophilia B in a mixed breed male dog: treatment of a hemorrhagic crisis with fresh frozen plasma].

A 6 months old male crossbred dog became conspicuous because of a considerable haematoma in the region of the left thigh without recognizable exterior trauma. The results of the screening tests of the haemostatic system (distinctly prolonged activated partial thromboplastin time [aPTT], normal thromboplastin time and platelet count as well as a shortening of thrombin time) yielded a tentative diagnosis of haemophilia. Haemophilia B could be diagnosed on the basis of a distinctly and isolated reduced factor IX activity (8%, reference range: 70-140%). Two infusions with 20 ml/kg BW fresh frozen plasma each caused a clear clinical recovery of the patient. In addition, the efficacy of plasma infusion was documented in vitro by a temporary increase of factor IX activity as well as repeated measurements with the resonance thrombograph and of the aPTT.