Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease in which the immune system makes antibodies that cause the blood to clot more easily. Clots can form in the veins, especially the deep veins of the legs, as well as in the arteries that carry blood to the brain, heart, kidneys, or other organs. In women, the syndrome can also disrupt blood flow to the placenta, leading to repeated miscarriages or pregnancy complications.

The syndrome can occur on its own (primary) or alongside another autoimmune disease, especially systemic lupus erythematosus (secondary). It affects more women than men and is usually diagnosed between young adulthood and middle age. Some people have antiphospholipid antibodies without ever having a clot; this is not yet called the syndrome, but the risk still needs to be assessed with a doctor.

Effects on the Heart and Blood Vessels

A common event is deep vein thrombosis in the legs, where a clot can break off and travel to the lungs, causing a pulmonary embolism. On the arterial side, stroke and transient ischemic attack (TIA), a temporary stroke, are common, so the syndrome should be looked for in young people who have a stroke with no clear cause. Antiphospholipid syndrome can also cause a heart attack at a young age, thickening or deposits on the heart valves, especially the mitral and aortic valves, and high pressure in the blood vessels of the lungs from repeated clots.

In a small number of people with the syndrome, clots form in many organs at once over a few days. This condition, called catastrophic antiphospholipid syndrome, is rare but is an emergency that requires intensive care.

Long-Term Treatment

Antiphospholipid syndrome cannot yet be cured, but the risk of clots can be lowered. After a clot, most people with the syndrome need long-term blood thinners, usually warfarin with INR monitoring. EULAR guidelines do not recommend rivaroxaban for people who are positive for all three antibodies, and direct oral anticoagulants are generally avoided after a clot in an artery. During pregnancy, doctors use heparin injections and aspirin because warfarin can harm the baby. With good treatment and monitoring, many people with the syndrome can lead active lives and go through pregnancy well.

Antiphospholipid syndrome is diagnosed when two things are present together: a clinical event, such as a blood clot or a pregnancy complication, and antiphospholipid antibodies that persist. The antibodies are checked with a blood test, which is repeated after at least 12 weeks, because antibodies can appear temporarily during an infection or while taking certain medicines.

Three types of antibodies are tested: lupus anticoagulant, anticardiolipin, and anti-beta2 glycoprotein I. Being positive for all three at once indicates a higher risk of clots. The 2023 ACR/EULAR classification criteria assign points for the type of clotting event, pregnancy complications, heart valve abnormalities, a low platelet count, and the antibody profile.

The timing of the test matters because blood thinners can affect lupus anticoagulant results. Your doctor also looks for lupus or other autoimmune diseases, as well as blood vessel risk factors such as high blood pressure, high cholesterol, and smoking.

See a doctor if you have had a blood clot or a pregnancy complication with no clear cause, especially at a young age. People with lupus are also advised to be tested for antiphospholipid antibodies. Go to the emergency room right away if you have sudden shortness of breath, chest pain, or signs of a stroke.

• Swelling and pain in one leg
• A history of repeated miscarriages or the death of a baby in the womb
• A stroke, transient ischemic attack, or heart attack before age 50
• Having lupus and planning a pregnancy
• Bruising, nosebleeds, or bleeding while taking blood thinners
• Purplish, net-like patches on the skin of the legs