Anti-cardiolipin antibodies (ACA) are antibodies often directed against cardiolipin and found in several diseases including syphilis, antiphospholipid syndrome, livedoid vasculitis, vertebrobasilar insufficiency, Behçet's syndrome, idiopathic spontaneous abortion, and systemic lupus erythematosus(SLE). They are a form of anti-mitochondrial antibody. In SLE, The anti-DNA antibodies and anti-cardiolipin act independently. In rheumatoid arthritis w/systemic sclerosis these antibodies may tie two conditions together. Anti-cardiolipin antibodies can be classified in two ways...