The antiphospholipid syndrome and SLE: is there a clue in the link between complement and coagulation?

The heterogenous immunoglobulins known as antiphospholipid antibodies (APLA) or lupus "anticoagulants" (LA) are prevalent in lupus patients and have been implicated in life-threatening thromboembolic events. Unfortunately, observing the presence of these antibodies in an individual does not predict the likelihood of an event nor does it predict when it may occur. A pathogenic role for these antibodies is supported by the observation that high titers and IgG isotype confer an increased risk of thromboembolism. Additionally, numerous reports indicate that isolated patient antibodies interfere with various elements of the coagulation cascade. Nevertheless, attempts to correlate specific antibody characteristics with the future likelihood of a hypercoagulable event in an individual patient have been unsuccessful to date. Given such uncertainty combined with the potential complications of anticoagulant medications, patients are generally not treated until significant morbidity has occurred. Finally, because of the apparent high rate of reoccurrence most patients must remain on anticoagulant therapy indefinitely, regardless of need.