The Hypercoagulable State in Canine Immune-Mediated Hemolytic Anemia

Immune-mediated hemolytic anemia (IMHA) is a condition in which autoantibodies bind to endogenous antigens on the erythrocyte membrane, leading to complement or antibody mediated red blood cell destruction. These antigens can be created as part of the normal immune response to an abnormal antigen (i.e. band-3, peroxiredoxin-2, or epitope created by an infectious disease) or due to an abnormal immune response to a normal antigen. 2 Agents that have been identified to lead to the formation of new epitopes on the surface of red blood cells include drugs, (ex. sulfonamides) infectious agents (ex. Babesia spp, Ehrlichia spp, Anaplasma phagocytophilum), vaccination and neoplasia. Recent studies, however, have failed to confirm an association between recent vaccination and the development of IMHA in dogs. 9-11 In most cases (approximately 70%), an underlying cause is not identified and the dog is classified as “idiopathic” or having primary IMHA. Thromboembolism is the most common and severe manifestation of the disease process, with studies identifying both arterial and venous thromboembolism on necropsy. 9, 13-16 The highest mortality rate occurs in the acute phase of the disease process and thromboembolic events are a major contributor to the mortality rate.