Antiphospholipid Antibody Syndrome

Antiphospholipid (AN-te-fos-fo-LIP-id) antibody syndrome (APS) is an autoimmune disorder. Autoimmune disorders occur if the body's immune system makes antibodies that attack and damage tissues or cells. 

Antibodies are a type of protein. They usually help defend the body against infections. In APS, however, the body makes antibodies that mistakenly attack phospholipids—a type of fat. 

Phospholipids are found in all living cells and cell membranes, including blood cells and the lining of blood vessels.

When antibodies attack phospholipids, cells are damaged. This damage causes blood clots to form in the body's arteries and veins. (These are the vessels that carry blood to your heart and body.)

Usually, blood clotting is a normal bodily process. Blood clots help seal small cuts or breaks on blood vessel walls. This prevents you from losing too much blood. In APS, however, too much blood clotting can block blood flow and damage the body's organs.


Some people have APS antibodies, but don't ever have signs or symptoms of the disorder. Having APS antibodies doesn't mean that you have APS. To be diagnosed with APS, you must have APS antibodies and a history of health problems related to the disorder.

APS can lead to many health problems, such as stroke, heart attack, kidney damage, deep vein thrombosis (throm-BO-sis), and pulmonary embolism (PULL-mun-ary EM-bo-lizm).

APS also can cause pregnancy-related problems, such as multiple miscarriages, a miscarriage late in pregnancy, or a premature birth due to eclampsia (ek-LAMP-se-ah). (Eclampsia, which follows preeclampsia, is a serious condition that causes seizures in pregnant women.)

Very rarely, some people who have APS develop many blood clots within weeks or months. This condition is called catastrophic antiphospholipid syndrome (CAPS).

People who have APS also are at higher risk for thrombocytopenia (THROM-bo-si-to-PE-ne-ah). This is a condition in which your blood has a lower than normal number of blood cell fragments called platelets (PLATE-lets). Antibodies destroy the platelets, or they’re used up during the clotting process. Mild to serious bleeding can occur with thrombocytopenia.

APS can be fatal. Death may occur as a result of large blood clots or blood clots in the heart, lungs, or brain.


APS can affect people of any age. However, it's more common in women and people who have other autoimmune or rheumatic (ru-MAT-ik) disorders, such as lupus. ("Rheumatic" refers to disorders that affect the joints, bones, or muscles.)

APS has no cure, but medicines can help prevent its complications. Medicines are used to stop blood clots from forming. They also are used to keep existing clots from getting larger. Treatment for APS is long term.

If you have APS and another autoimmune disorder, it's important to control that condition as well. When the other condition is controlled, APS may cause fewer problems.


Source: National Heart, Lung, and Blood Institute, National Institutes of Health.