Antiphospholipid Syndrome (APS) is an autoimmune disease which can cause frequent clotting in arteries and veins and/or miscarriages. The clotting results from the presence of proteins in the blood called anti-phospholipid autoantibodies (commonly called aPL) formed against the person’s own tissues. These autoantibodies affect the normal clotting process, leading to increased clot formation or thrombosis (in which blood flow stops due to a clot). The damage caused by this clotting can vary depending on the site of the clot. Blood clots in the arteries in the heart can lead to heart attacks, while blood clots in the arteries in the brain can result in strokes.