Prekallikrein inhibition associated with the lupus anticoagulant: a mechanism of thrombosis.

The lupus anticoagulant was identified in three patients. Laboratory studies gave evidence of inhibitory activity directed against phospholipid and prekallikrein. Inhibition of prekallikrein has not been reported previously. When exposed to kaolin, all three patients' plasmas failed to develop the level of fibrinolytic activity achieved by similarly treated normal plasma. The data suggest that compromised fibrinolytic capacity may be a contributing factor in the development of thrombosis in patients with the lupus anticoagulant.