The objective of this work was to review current data about the pathophysiology, clinical features, and treatment of thrombotic microangiopathies. Thrombotic microangiopathies are microvascular occlusive disorders characterized by systemic or intrarenal aggregation of platelets, thrombocytopenia, and mechanical injury to erythrocytes. In thrombotic thrombocytopenic purpura, systemic microvascular aggregation of platelets causes ischemia in the brain and other organs. In the hemolytic-uremic syndrome, platelet-fibrin thrombi occlude predominantly the renal circulation. Thrombotic microangiopathy is a rare disorder whose varied clinical manifestations result from the formation of platelet-rich thrombi within the microvasculature and consequent tissue ischemia. The clinical features are acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. This diagnosis is of considerable importance because of the possible fulminant clinical course. Some atypical forms may be unrecognized. Plasma exchange is the current reference treatment of thrombotic thrombocytopenic purpura. However, in the light of recent publications, either infusions of concentrates of purified enzyme or more intensive immunosuppressive therapy would be more specific.