Antiphospholipid syndrome (APS) is an autoimmune disease associated with frequent clotting in arteries and veins and fetal losses. The clotting results from the presence of proteins in the blood—called antiphospholipid autoantibodies (aPL)—formed against the person’s own tissues.
In circulation, these autoantibodies are able to interfere with some mechanisms of coagulation leading to clot formation or thrombosis (venous and/or arterial). The damage caused by this clotting can vary depending on the formation site. For instance, repeated small thrombotic events may cause heart problems (cardiac valve thickening or damage) with the risk of releasing clots into blood (arterial embolism).
Thrombosis in the arterial circulation can occur anywhere in the body, but usually happens in the brain, which can cause strokes. Patients with arterial clots can also exhibit problems in movement or vision, and repeated clots can lead to cognitive impairment.
Why patients develop these autoantibodies is not yet completely understood. Some evidence points to environmental factors, such as infections, and a genetic predisposition as playing a role in triggering the production of these autoantibodies.
APS affects women five times more often than men. It is typically diagnosed between age 30 and 40. According to patient–fact sheet author, Pier Luigi Meroni, MD, “up to 40 percent of patients with SLE will test positive for the antiphospholipid autoantibodies, and only half will develop thrombosis and/or experience fetal losses.” Like most autoimmune disorders, APS has a genetic component, although there is not a direct transmission from parent to offspring.
APS is diagnosed with a blood test for aPL given to patients with thrombosis or miscarriage. Screening is done using two kinds of assays—a clotting functional assay (the Lupus Anticoagulant test) and solid-phase assays (the anticardiolipin and the anti–b 2 glycoprotein I antibody test). Tests vary because of the differences in the aPL population. Each single test cannot detect all the possible autoantibodies, so their combined use is advised. At least one of these tests must prove positive and be confirmed in two occasions no less than three months apart to rule out transient positivity. Most often, aPL is detected after a thrombotic event or recurrent miscarriages; therefore, the main goal is prevention of recurrences, given the fact that the persistent presence of the antibodies puts the patient at strong risk for future episodes.
Acute thrombotic events (both arterial and venous) are treated as for all kinds of thromboses, independently of the presence of aPL. Typically, the blood is anticoagulated using heparin infusion into the veins, followed by oral anticoagulant drugs (e.g., coumadin). Some patients are also given compounds that dissolve clots. Subcutaneous injections of heparin and low-dose aspirin are the standard therapy for preventing new miscarriages. The therapy is started at the beginning of the pregnancy and continued in the period immediately after the delivery. This therapeutic approach has been shown to be effective in the majority of the cases, leading to the delivery of healthy babies. In nonresponsive cases, alternative therapies, such as intravenous immunoglobulin infusions, may help.