Antiphospholipid and thrombosis syndromes.

ACAs and the lupus anticoagulant are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism or mechanisms whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories, as previously discussed, have been advanced. The most common thrombotic events associated with ACAs are DVT and PE (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), cerebrovascular or retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). The relative frequency of ACAs in association with arterial and venous thrombosis strongly suggests that these should be looked for in any patient with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through IV) should be defined, if possible, because this may dictate both type and duration of both immediate and long-term anticoagulant therapy. Unlike those with ACAs, patients with primary lupus anticoagulant thrombosis syndrome usually have venous thrombosis. Since the aPTT is unreliable in patients with lupus anticoagulant and is not usually prolonged in patients with ACAs, definitive tests (ELISA for ACA and the dRVVT for lupus anticoagulant) should be immediately ordered when suspecting antiphospholipid syndrome or in patients with otherwise unexplained thrombotic or thromboembolic events.