Antiphospholipid syndrome occurs when your immune system mistakenly creates antibodies that make your blood much more likely to clot. Antibodies normally protect the body against invaders, such as viruses and bacteria.
Antiphospholipid syndrome can be caused by an underlying condition, such as an autoimmune disorder, infection or certain medications. You also can develop the syndrome without an underlying cause.
This can cause dangerous blood clots in the legs, kidneys, lungs and brain. In pregnant women, antiphospholipid syndrome also can result in miscarriage and stillbirth.
There's no cure for antiphospholipid syndrome, but medications can reduce your risk of blood clots.