Antiphospholipid antibody syndrome.

Autoimmune aPL are associated with a well-defined clinical syndrome of vascular thromboses, recurrent fetal loss, thrombocytopenia, livedo reticularis, and valvular and neurologic abnormalities. A clinical diagnosis of SLE need not be present, and aPL syndrome in the absence of other well-defined autoimmune disease is termed PAPS. A positive test for aPL is defined by enzyme-linked immunoassay (aCL) or by functional coagulation assay (LAC). Anticardiolipin antibody and LAC are similar but probably not identical antibodies. The false-positive test for syphilis is less closely associated with clinical complications than are aCL and LAC. The mechanism of action of aPL is not yet known, although many theories have been advanced. Recent identification of beta 2-glycoprotein I, a serum glycoprotein, as an aPL cofactor suggests that inhibition of this protein's anticoagulant activity may be important. Autoimmune aPL differ from infection-induced aPL in important antibody characteristics, including IgG subclass, light chain preference, antibody avidity, and cofactor requirement. Both recognize negatively charged phospholipids, but various physical characteristics of the phospholipids alter the recognition patterns. Treatment of the aPL syndrome is not well defined. Anticoagulation with heparin, coumadin, or aspirin are currently widely used. Although corticosteroid, immunosuppressive therapy, and plasmapheresis may be used for severe, fulminant thrombosis, the efficacy of this treatment has yet to be proved.