Thrombotic thrombocytopenic purpura and related disorders

Abstract

This article provides us with background information on the disease. Clinical features, variants and classification, laboratory findings, and pathology are discussed. Knowledge of the disease's pathogenesis has increased recently and specific causes discussed are predisposing factors, triggering agents, endothelial damage, defective PGI2 bioavailability, FVIII/vWF multimeric structure abnormalities, platelet activation, and hemolytic anemia. Proposed specific therapies discussed are steroids, heparin, antiplatelet agents, prostacyclin, splenectomy, immunosuppressive agents, plasma infusion, and plasma exchange.

PIP: Thrombotic thrombocytopenic purpura (TTP) is a syndrome that occurs mainly in adults with multiorgan microvascular thrombosis consisting of thrombocytopenia, microangiopathic hemolytic anemia, neurologic symptoms, renal involvement, and fever. The female to male ratio is 3:2, and peak incidence occurs in the 3rd decade of life. Clinical signs are the consequence of hyaline thrombosis and occlusion of capillaries and arterioles. Renal ailment manifests itself in hematuria and proteinuria with azotemia and even overt renal failure. In severe disease, azotemia is typical of hemolytic uremic syndrome (HUS). TTP was first described in 1925 by Moschcowitz. The clinical picture of TTP consists of a prodromal phase, a viruslike disease occurring in up to 40% of patients. 60% have neurologic disturbances, 90% have purpura initially, and fever occurs in all. Anemia is often severe with hemoglobin values of 7-9 gm/dl, renal involvement in 90%, and renal failure in 40-80% of patients. Clinical variants include the acute and fulminant variety mortality, the chronic form, and the relapsing form. Predisposing factors and triggering agents are autosomal recessive inherited traits in acute idiopathic TTP, systemic diseases, tumor antigens, pregnancy and puerperium, viruses (endotoxins for HUS), and possibly oral contraceptives and hypertension. Therapy includes corticosteroids (prednisone 100-400 mg/day); heparin for postpartum HUS; and antiplatelet agents (Dextran 70, aspirin, and dipyridamole in high doses). The infusion of PGI2 is controversial; splenectomy is also questionable; and vincristine, azathioprine, and cyclophosphamide have unproven efficacy. Fresh-frozen plasma exchange is the method of choice as it produces survival in 90%. Others are iv immunoglobulins, vitamin E, and dialysis and renal transplant. Platelet transfusions are contraindicated because of sudden death and decreased survival.