The 'antiphospholipid syndrome' and the 'lupus anticoagulant'.

In recent years an association has been described between, on the one hand, an in vitro prolongation of phospholipid-dependent coagulation tests (the 'lupus anticoagulant') or the demonstration of antiphospholipid antibodies and, on the other, clinical events, particularly recurrent thrombosis (usually venous but sometimes arterial), thrombocytopenia, and also recurrent mid-term fetal loss. Other less well-documented associations with haemolytic anaemia, livedo reticularis, strokes and other neurological syndromes have been suggested. The antibodies are present temporarily in many infections, are usually of IgM isotype and thrombosis does not occur. However, they are persistently present and mainly of IgG isotype in a number of auto-immune disorders associated with thrombosis, in particular systemic lupus erythematosus, in which 50% of patients will show antibody of one isotype or another. The strongest association is with antinuclear factor-negative lupus and 'lupus-like' disorders in which a full diagnosis of classical lupus cannot be made. The clotting test abnormality and antiphospholipid antibodies may be found also in otherwise normal individuals suffering thrombosis or fetal loss--the so-called primary antiphospholipid syndrome. These data raise important questions for management, but many details are controversial despite a decade's work; this review examines the present position and outlines some of the difficulties, particularly from the point of view of nephrology and paediatrics.