Contributor: Gordon K. Klintworth
Thrombotic thrombocytopenic purpura is a rare disorder associated with a diffuse platelet activation and aggregation with a widespread deposition of platelets in the microcirculation. The clinical features include thrombocytopenia, microangiopathic hemolytic anemia [anemia - microangiopathic hemolytic], fever, central nervous system dysfunction and renal disease. Widespread purpura is often present. The platelet count is often <20,000/ml. The cause of the disorder remains uncertain, but an inappropriate release of von Willebrand factor from injured vascular endothelium into the circulation may play a role. Thrombotic thrombocytopenic purpura usually develops in otherwise healthy persons, but it may complicate numerous autoimmune diseases (systemic lupus erythematosis, rheumatoid arthritis, Sjögren syndrome), drug-induced hypersensitivity [hypersensitivity - drug-induced], infections, cancer chemotherapy, and pregnancy. Throughout the body arterioles and capillaries are occluded by microthrombi containg platelet aggregates, fibrin and some erythrocytes and leukocytes. The vascular wall lacks inflammation. Treatment is by plasma infusion and plasmapheresis. Normal coagulation tests (prothrombin time, partial thromboplastin time, activated partial thromboplastin time, fibrinogen concentration) distinguish thrombotic thrombocytopenia purpura from disseminated intravascular coagulation.