Autoimmune Thrombocytopenic Purpura

Platelets play a central role in the maintenance of normal hemostasis and vascular repair. Decreased platelet numbers (thrombocytopenia) can result in bruising, petechiae, or even life-threatening bleeding. Purpura is a large area of purplish or brownish red discoloration, easily visible through the skin, caused by bleeding into the tissues. The skin is of normal thickness.

In humans, immune-mediated thrombocytopenic purpura (ITP) is one of the most common forms of autoimmune disease affecting both adults and children. The thrombocytopenia of this disorder is associated with autoantibodies that are directed against various platelet membrane receptors, including platelet glycoproteins such as glycoprotein IIb/IIIa (GPIIb/IIIa) or GPIb/IX complexes. Binding of autoantibodies to these target antigens eventually results in platelet destruction by the reticuloendothelial system.

Two Forms of Autoimmune Thrombocytopenic Purpura

This disease occurs in acute and chronic form. Adults who develop ATP generally develop the chronic variety, which remains permanently with the patient. In this condition, bleeding may occur from mucous membranes (mouth and nose), gastrointestinal tract and urinary bladder. Animals usually bruise easily and have prolonged bleeding after trauma.

Treatment of Autoimmune Thrombocytopenic Purpura

Treatment is directed towards maintaining the patient free of purpura, not restoring the platelet count to normal. Approximately 50% of patients respond to steroids by a significant elevation of platelet count and improvement of purpura. However, cessation of therapy results in eventual relapse if the disease is of the chronic variety. Immunosuppressive therapy is effective in approximately one-third of patients with the chronic form of the disease, but often relapses occur, requiring maintenance therapy with potentially harmful drugs.

Breeds at Risk

In dogs there is marked disease predisposition in poodles, German Shepherd Dog and Cocker Spaniels.

References:
1. S Karpatkin. Autoimmune thrombocytopenic purpura. Volume 56, Issue 3, pp. 329-343, 09/01/1980
2. Mei Chang, Peggy A. Nakagawa, Shirley A. Williams, Michael R. Schwartz, Karen L. Imfeld, Jeffrey S. Buzby, and Diane J. Nugent. Immune thrombocytopenic purpura (ITP) plasma and purified ITP monoclonal autoantibodies inhibit megakaryocytopoiesis in vitro. The American Society of Hematology. Blood, 1 August 2003, Vol. 102, No. 3, pp. 887-895
3. Bernard F. Feldman, Joseph G. Zinkl, Nemi Chand Jain. Schalm's Veterinary Hematology