Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HU S) are multisystemic disorders that are characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic manifestations, resulting f rom platelet agglutination in the arterial microvasculature. Until the Intr oduction of plasma-based therapy, TTP was associated with a mortality rate greater than 90%. Current outcomes of TTP and HUS have improved dramaticall y with the use of plasma exchange, which should be initiated promptly at di agnosis. Recent evidence suggests that deficiency of a specific plasma prot ease responsible for the physiologic degradation of von Willebrand factor p lays a pathogenic role in a substantial proportion of familial and acute id iopathic cases of TTP. Although multiple triggers, such as infection, drugs , cancer, chemotherapy, bone marrow transplantation, and pregnancy, are rec ognized, knowledge of the pathogenesis of TTP and HUS in relationship to th ese disorders remains incompletely understood and continues to evolve. Whil e uncommon, TTP and HUS are of considerable clinical importance because of their abrupt onset, fulminant clinical course, and high morbidity and morta lity in the absence of early recognition and treatment.