Inherited deficiencies of inhibitors (antithrombin, protein C, protein S, plasminogen activator inhibitor) are quite uncommon in animals. In human patients, inherited deficiencies in inhibitors (or abnormalities in their targets that prevent inhibition) predispose the patient to deep venous or arterial thrombosis. Acquired abnormalities in inhibitors are seen in animals (please refer to inhibitor tests or antithrombin and protein C for more information).