TTP (thrombotic thrombocytopenic purpura):A life-threateningdiseaseinvolvingembolismandthrombosis(plugging) of the smallbloodvesselsinthebrain. It is usually caused by inhibition of anenzymecalled ADAMTS13 which normally serves to break up a bloodproteincalled Von Willebrand Factor into smaller pieces.TTPis characterized byplateletmicrothrombi (tiny traveling clots composed ofplatelets, the clotting cells in the blood), thrombocytopenia (lack of platelets),hemolytic贫血(红细胞的破裂),feve型r,renal(kidney) abnormalities and neurologic changes such asneurologicalsigns 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 use ofplasmaexchange (running blood through a machine to which thepatientis connected which removes the plasma or fluid portion of the blood and returns the cells mixed with new plasma from donors and other fluids) has greatly reduced thedeath ratefrom TTP. Themortality(death) rate for promptly treated cases ranges from 10 to 20 percent, down from 90% before the use of plasma exchange technique.
Many drugs have been associated with TTP. One is the antiplatelet drugclopidogrel(Plavix).
