Recurrent antiphospholipid-related deep vein thrombosis as presenting manifestation of systemic lupus erythematosus

Antiphospholipid antibodies (aPL) are frequently associated with thrombotic disorders in the so-called antiphospholipid syndrome. Together with antica rdiolipin antibodies (aCL), lupus anticoagulant (LA) is the main diagnostic tool for aPL detection. Since LA determination is based on the finding of prolonged clotting time in vitro, concomitant anticoagulant therapy may sig nificantly interfere with its detection. We report a case of a boy in whom recurrent aPL-related thrombosis heralded for several months the onset of s ystemic lupus erythematosus (SLE). Abnormally increased in vitro clotting t imes at the time of the second thrombotic event led to the suspicion of the presence of LA activity. However, this latter finding was difficult to int erpret since the patient was already on heparin treatment at the time of ou r first observation. Thus, LA was assayed using a commercial kit in which a heparin neutralizer is included (Staclot LA). Two consecutive samples from the patient were compared with eight patients on anticoagulant therapy for non-aPL-related thrombotic events and 20 healthy controls. The study showe d that, taking into account the concomitant anticoagulant treatment, Staclo t LA was positive only in the propositus, raising the suspicion of a possib le aPL-related origin of the thrombotic event. This issue was definitively confirmed in a subsequent follow-up. Conclusion The present report shows that aPL-related deep vein thrombosis c an be the earliest clinical manifestation of pediatric SLE, and that Staclo t LA may have a role in LA detection during the course of anticoagulant tre atment.