Thrombotic thrombocytopenia purpura (TTP) is a rare, serious blood disease. There is an acquired/autoimmune form of the disease referred to as immune mediated TTP (iTTP) and a congenital form of the disease (cTTP). Major symptoms may include a severe decrease in the number of blood platelets (thrombocytopenia), abnormal destruction of red blood cells (hemolytic anemia) and disturbances in the nervous system, heart and other organs occur because of small clots that form in the smallest arteries. The exact cause of TTP is unknown.