Definition of TTP (thrombotic thrombocytopenic purpura)

TTP (thrombotic thrombocytopenic purpura): A life-threatening disease involving embolism and thrombosis (plugging) of the small blood vessels in the brain. TTP is characterized by platelet microthrombi (tiny traveling clots composed of platelets, the clotting cells in the blood), thrombocytopenia (lack of platelets), hemolytic anemia (from the breakup of red blood cells), fever, renal (kidney) abnormalities and neurologic changes such as neurological signs such as aphasia, blindness, and convulsions.

TTP is fortunately rare. It occurs at a rate of 3.7 cases per year per million persons. The mortality (death) rate for promptly treated cases ranges from 10 to 20 percent.

Many drugs have been associated with TTP. One is the antiplatelet drug clopidogrel (Plavix).