Bleeding diatheses may be caused by congenital or acquired defects in the vasculature, platelets, or the coagulation proteins. Congenital or acquired defects or deficiencies of platelets usually manifest as superficial petechial and ecchymotic hemorrhages (especially of mucous membranes), epistaxis, melena, or prolonged bleeding at injection and incision sites, while congenital or acquired deficiencies in coagulation proteins usually manifest clinically as delayed deep tissue hemorrhage and hematoma formation.

Pathologic thrombosis may occur because of primary or inherited disorders of anticoagulant protein factors or because of secondary or acquired disorders. Collectively, these conditions are called hypercoagulable states. Systemic syndromes such as disseminated intravascular coagulation (DIC) that enhance platelet responsiveness to agonists alter the balance between anticoagulant and procoagulant protein factors, or increase the reactivity of endothelium are more common in animals than inherited disorders.

Last full review/revision July 2011 by Annemarie T. Kristensen, DVM, PhD, DACVIM (Small Animal), DECVIM-CA & Oncology; Bo Wiinberg, DVM, PhD