Anticardiolipin antibodies and thrombosis.

Anticardiolipin antibodies (ACLAs) are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby ACLAs alter hemostasis to induce a hypercoagulable state remain unclear, several theories, as previously discussed, have been advanced. The most common thrombotic events associated with ACLAs are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome), or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). The relative frequency of ACLAs in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual 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.