Antiphospholipid syndrome is a systemic autoimmune inflammatory disorder in which a person’s immune system makes antibodies that can cause the formation blood clots in the blood vessels as well as pregnancy problems. Blood clotting (thickening of the blood) is a normal function of the body. It is what stops the bleeding when we get a cut. But blood clots that form inside the blood vessels are dangerous, and the overactive blood clotting associated with APS can cause life-threatening health problems.