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What is antiphospholipid syndrome?

Antiphospholipid syndrome (APS) is an autoimmune disorder and a hypercoagulable disorder. It is associated with the production of one or more antiphospholipid antibodies. These are autoantibodies that target the lipid-proteins found in the outermost layer of cells (cell membranes) and platelets. The autoantibodies interfere with the blood clotting process in a way that is not fully understood. APS is also associated with thrombotic episodesthrombocytopenia and with pregnancy complications such as pre-eclampsia and recurrent miscarriages. There is now good evidence to suggest the effects on the placenta are different from the effects on blood vessels and inflammation.

The main antiphospholipid antibodies associated with APS include lupus anticoagulantcardiolipin antibody and beta-2 glycoprotein 1 (β2GP1) antibody. These antibodies increase an affected person's risk of developing recurrent inappropriate blood clots in both veins and arteries. Those with APS may experience a single thrombotic episode or have multiple occurrences. Symptoms and complications may range from mild to critical. Blood clots that form can obstruct blood flow and can damage tissues and organs. If they are carried to the lungs, heart, brain or kidneys, they can cause a pulmonary embolismheart attackstroke and/or kidney damage. A small subset of people with APS may have widespread thrombotic disease with damage to many of the large internal organs of the body (viscera), referred to as catastrophic APS.

Those with antiphospholipid antibodies may have APS and another co-existing autoimmune disorder such as systemic lupus erythematosus (SLE) or may have one or more of the antibodies present with no associated symptoms. Antiphospholipid antibodies may be seen in those with HIV, some cancers, in the elderly and temporarily, with infections (e.g. Q fever) and with drugs such as phenothiazines and procainamide. They may also be found in 1 per cent to 5 per cent of healthy people.

Antiphospholipid syndrome may affect anyone but is most frequently seen in women of child-bearing age and in those with another autoimmune disorder. According to the March of Dimes, APS is the most common acquired thrombophilia, affecting up to 5 per cent of pregnant women.

Last Review Date: March 15, 2016