Thrombotic microangiopathy. Pisoni R, Remuzzi G. European Journal of Internal Medicine 2000;11(3):135-139.

The term 'thrombotic microangiopathy' (TMA) describes syndromes of microangiopathic hemolytic anemia, thrombocytopenia, and variable signs of organ impairment, due to platelet aggregation in the microcirculation. The term 'hemolytic uremic syndrome' (HUS) has entered clinical use to describe childhood cases of TMA dominated by renal impairment, while the term 'thrombotic thrombocytopenic purpura' (TTP) refers to adult cases of TMA with predominant neurological abnormalities. This paper provides an overview of the pathophysiology, epidemiology, clinical manifestations, and management of TMA. Most relevant is the treatment outcomes of HUS and TTP. Supportive therapy is the treatment of choice in diarrhea-positive HUS with spontaneous recovery within a few weeks in about 85-95% of patients. In the absence of a controlled, clinical trial, the efficacy of antibiotic treatment on the prevention and amelioration of HUS is unproven, apart from forms caused by Shigella dysenteriae. Antibiotics may increase the risk of developing HUS in children with hemorrhagic colitis associated with E. coli O157:H7 infection. Steroids are not effective and anticoagulants and antiplatelets increase the risk of hemorrhage. Infusion of vitamin E gave encouraging results in uncontrolled studies that have to be confirmed in controlled studies. A number of other possible treatments which would inactivate the verotoxin are under study. Plasma therapy is recommended, on the other hand, for adults, in cases with neurological involvement, in recurrent, and in familial forms of HUS. Survival in acute TTP has improved with earlier diagnosis, intensive care facilities, and new therapeutic techniques. At present, the most effective treatment is plasma exchange or infusion. These latter two therapies have been shown to be equally effective. Most study findings suggest that plasma exchange is the first choice since a limited amount of plasma can be provided with infusion, which limits the response to therapy. Most patients achieve complete recovery within 5 to 7 days of treatment, but occasionally very prolonged treatment is necessary to achieve remission. Corticosteroids are beneficial in less severe cases. Plasma therapy consistently induces remission in patients with chronic relapsing TTP but it fails to prevent recurrences. Vincristine is occasionally effective in plasma-resistant TTP and may stop or delay recurrences in chronic relapsing TTP. The effectiveness of immunoglobulins is not known. Splenectomy is usually not effective in plasma-resistant TTP but it may help to prolong disease-free intervals. Platelet transfusions may be used only in life-threatening bleeding.