In addition to the cerebrovascular effects, livedo reticularis, venous thrombosis, usually in the legs, and late pregnancy loss are other features. Eclampsia and pre-eclampsia and the syndrome of HELLP during pregnancy are the result of the autoantibodies. Often the antiphospholipid syndrome is identified in asymptomatic patients during the evaluation of elevated partial thromboplastin time (PTT) or thrombocytopenia; severe reductions in platelet count (below 20 × 109/L) are, however, uncommon.
Testing for this disease consists of detection of IgM, IgG, and mixed antibodies to each of these three main phospholipids (lupus anticoagulant, anticardiolipin, and β2-GP 1); there is a partial overlap in many patients, in which more than one antibody subclass is present against more than one lipoprotein—80 percent of patients with lupus anticoagulant have anticardiolipin antibody but fewer than 50 percent of those with anticardiolipin antibody have lupus anticoagulant. Antibodies to β2-glycoprotein 1 are most specific for the disease. Nonetheless, the main laboratory feature of the illness is a prolonged partial thromboplastin time. The titer of anticardiolipin broadly correlates with the risk of thrombosis and the specificity for the syndrome is higher for IgG than for IgM autoantibodies. An increased incidence of migraine has long been discussed and also disputed. A review of strokes in this condition has been given by Levine and colleagues (1990) and a overview of the topic as it applies to in general medicine, by Garcia and Erkan.
These comments pertain mainly to a “primary” idiopathic autoimmune form of the disease but cases occur secondarily to lupus erythematosus, Sjögren disease, neuroleptic drugs such as the phenothiazines, butyrophenones and others drugs, and to certain infections.
The most frequent neurologic abnormality is a TIA, often taking the form of amaurosis fugax (transient monocular blindness), with or without retinal arteriolar or venous occlusion (Digre et al). Stroke-like phenomena are more frequent in patients who also have migraine, hyperlipidemia, or antinuclear antibodies, and in those who smoke or take birth control pills. Almost one-third of the 48 patients reported by Levine and associates (1990) had thrombocytopenia and 23 percent had a false-positive Venereal Disease Research Laboratory (VDRL) test. The vascular lesions are mainly in the cerebral white matter and are infarcts, seen well with MRI. Angiography reveals occlusions of arteries at unusual sites (Brey et al). The mechanism of stroke is not entirely clear and may derive from emboli originating on mitral valve leaflets similar to nonbacterial thrombotic endocarditis; alternatively, and more likely in our view, there is a noninflammatory in situ thrombosis of medium-sized cerebral vessels, as suggested by the limited pathologic material studied by Briley and colleagues.