Lupus anticoagulants: misnomer, paradox, riddle, epiphenomenon.

Lupus anticoagulants (LA) were originally described in patients with systemic lupus erythematosus (SLE) and clinical bleeding. Following the original description, they were associated with numerous clinical conditions and it was soon appreciated that there was not an increased risk of hemorrhage. Hence the name is a misnomer which has resisted attempts at modification. The paradox of LA is the apparent increased risk of both arterial and venous thromboembolic events. Thus, a laboratory finding which was once associated with bleeding and subsequently was regarded as a nuisance has now acquired new respectability as a marker of a thrombotic predisposition. The riddle of the anticoagulant effect in vivo and the apparent procoagulant effect in vivo remains unsolved. Perhaps it is an epiphenomenon, but more importantly, it may open the door to greater understanding of the delicate regulatory systems which prevent thrombosis. LA exist in virtually every patient population. Therefore, they are no longer a topic of interest limited to hematologists, rather they have achieved multidisciplinary attention. Laboratories are now being asked to prospectively evaluate patients for the presence of LA or antiphospholipid antibodies (APA). The evaluation of LA, both in the research laboratory and clinic, should continue to provide important insights applicable to a variety of specialties.