Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome. Elliott MA, Nichols WL. Mayo Clinic Proceedings 2001;76(11):1154-1162.

ABSTRACT:

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are multisystemic disorders that are characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic manifestations, resulting from platelet agglutination in the arterial microvasculature. Until the introduction of plasma-based therapy, TTP was associated with a mortality rate greater than 90%. A randomized controlled trial comparing plasma infusion with plasma exchange (PE)therapy definitively confirmed the superiority of the latter with a response rate of 78%. HUS patients treated with PE therapy also had equally favorable results, challenging the common belief that PE is less effective for HUS than TTP. Current outcomes of TTP and HUS have improved dramatically with the use of PE, which should be initiated promptly at diagnosis. Although evidence from a randomized trial is lacking, prednisone has been recommended due to the recent demonstration of an autoimmune pathogenesis in a substantial proportion of patients with Thrombotic Thrombocytopenic Purpura. Antiplatelet agents and platelet transfusions are not recommended in TTP. Recent evidence suggests that deficiency of a specific plasma protease responsible for the physiologic degradation of von Willebrand factor plays a pathogenic role in a substantial proportion of familial and acute idiopathic cases of TTP. Although multiple triggers, such as infection, drugs, cancer, chemotherapy, bone marrow transplantation, and pregnancy, are recognized, knowledge of the pathogenesis of TTP and HUS in relationship to these disorders remains incompletely understood and continues to evolve. While uncommon, TTP and HUS are of considerable clinical importance because of their abrupt onset, fulminant clinical course, and high morbidity and mortality in the absence of early recognition and treatment. New insights into the pathogenesis of TTP and HUS promise to further improve the management and outlook of these potentially devastating syndromes.