Acquired autoimmune thrombotic thrombocytopenic purpura (TTP)-the most common form of TTP-is a life-threatening hematologic disease characterized by hemolytic anemia and thrombocytopenia. Acquired autoimmune TTP can cause signs and symptoms of neurologic and other organ involvement, with mortality approaching 90% if the disease is not promptly recognized and treated. Since the introduction of plasma exchange in 1991, the acquired autoimmune TTP survival rate has increased to 78%.