Antiphospholipid syndrome (APS), also called antiphospholipid antibody syndrome (APLS), is an autoimmune disorder in which the immune system produces abnormal antibodies called antiphospholipid antibodies. These antibodies can increase the tendency of the blood to form abnormal clots in veins or arteries. Blood clots caused by APS may affect different parts of the body, including the legs, lungs, brain, heart, kidneys and other organs. In women, APS can also cause pregnancy-related complications, including recurrent miscarriage, stillbirth and other problems related to the placenta. APS can occur on its own, known as primary APS, or together with another autoimmune disease, particularly systemic lupus erythematosus (SLE or lupus). The condition can affect people of any age, although it is more commonly diagnosed in adults.
The symptoms of APS vary depending on where a blood clot develops. Some people with antiphospholipid antibodies never develop symptoms or blood clots, while others may experience recurrent clotting problems. Common signs and complications include:
Blood clots in the legs: A clot in a deep vein, known as deep vein thrombosis (DVT), may cause pain, swelling, warmth or redness in the affected leg.
Pulmonary embolism: A blood clot can travel from the leg to the lungs and cause sudden shortness of breath, chest pain, rapid heartbeat or coughing, sometimes with blood.
Stroke: A clot affecting blood flow to the brain can cause sudden weakness, numbness, difficulty speaking, confusion or loss of coordination.
Transient ischemic attack (TIA): A temporary interruption of blood flow to the brain can produce stroke-like symptoms that resolve, but a TIA is an important warning sign of possible future stroke.
Repeated miscarriages or pregnancy complications: APS may increase the risk of recurrent pregnancy loss, stillbirth, premature birth and complications involving the placenta.
Low platelet count: Some people with APS develop thrombocytopenia, meaning they have fewer platelets than normal.
Skin changes: A mottled, lace-like skin pattern called livedo reticularis may occur. Skin ulcers can also develop in some people.
Kidney problems: Blood clots affecting the small blood vessels of the kidneys can impair kidney function.
Heart-related complications: APS can contribute to blood clots affecting the coronary arteries and, in some cases, problems involving heart valves.
Other blood clots: Clots may occur in unusual locations, such as the veins of the abdomen or the vessels supplying other organs.
APS develops when the immune system produces antiphospholipid antibodies. These antibodies are directed against certain proteins that bind to phospholipids, which are important components of cell membranes and are involved in normal blood-clotting processes. The main antiphospholipid antibodies associated with APS are:
Lupus anticoagulant
Anticardiolipin antibodies
Anti-beta-2 glycoprotein I antibodies
The presence of these antibodies does not automatically mean that a person has APS. Some people have antiphospholipid antibodies but never develop abnormal blood clots or pregnancy complications. A diagnosis of APS generally requires both appropriate clinical findings and persistent laboratory evidence of antiphospholipid antibodies.
The exact reason why some people develop APS is not always known. Several factors may be associated with the development of antiphospholipid antibodies or with an increased risk of clotting. Possible factors include:
Other autoimmune diseases, especially lupus
Certain infections
Some medications
Genetic or inherited factors
Smoking
Prolonged immobility
Surgery
Pregnancy and the postpartum period
Hormonal treatments containing estrogen
Other conditions that increase the risk of blood clots
Having one or more risk factors does not necessarily mean that a person will develop APS.
Secondary APS occurs in association with another autoimmune condition. It is particularly associated with systemic lupus erythematosus (SLE), although other autoimmune disorders may also occur alongside APS.
Catastrophic antiphospholipid syndrome (CAPS) is a rare and severe form of APS in which widespread blood clots develop over a short period and affect multiple organs. CAPS is a medical emergency that requires immediate hospital treatment.
APS is an important cause of certain pregnancy complications because blood clots and inflammation can interfere with the blood supply to the placenta. Possible pregnancy complications include:
Recurrent miscarriage
Stillbirth
Restricted fetal growth
Premature birth
High blood pressure during pregnancy
Preeclampsia
Placental problems
Women with APS who are pregnant or planning pregnancy should receive medical care from an appropriate specialist. With proper monitoring and treatment, many women with APS can have successful pregnancies.
Diagnosing APS involves reviewing the patient’s medical history, examining symptoms and performing blood tests. Doctors may test for:
Lupus anticoagulant
Anticardiolipin antibodies
Anti-beta-2 glycoprotein I antibodies
A positive antibody test alone is not sufficient to diagnose APS. The antibodies generally need to remain detectable on repeat testing performed at least 12 weeks apart, together with a relevant clinical event such as an abnormal blood clot or specific pregnancy complication. Doctors may also perform imaging tests to identify blood clots, depending on the symptoms. For example:
Ultrasound may be used to detect a clot in a leg vein.
CT or MRI may be used when a clot in the brain or another organ is suspected.
CT pulmonary angiography may be used when pulmonary embolism is suspected.
Other blood tests may be performed to assess platelet levels, kidney function, liver function and other conditions that may influence treatment.
There is currently no treatment that permanently removes antiphospholipid antibodies from the body. Treatment focuses mainly on preventing and treating abnormal blood clots and reducing pregnancy complications.
People who have experienced blood clots due to APS are commonly treated with anticoagulant medicines, often for a prolonged period.
Medicines that may be used include:
Warfarin
Heparin
Low-molecular-weight heparin
The choice of anticoagulant depends on the person’s medical history, pregnancy status, other medications and risk factors.
Women with APS may be treated with medicines such as low-dose aspirin and heparin or low-molecular-weight heparin, depending on their individual history and risk profile. Warfarin is generally avoided during pregnancy because it can harm the developing fetus, although treatment decisions should always be made by the treating specialist.
In people with APS associated with another autoimmune condition, such as lupus, doctors may prescribe additional medicines to control the underlying disease. Treatment should always be individualized. Patients should not start, stop or change anticoagulant medication without medical advice.
It is important to distinguish between having antiphospholipid antibodies and having antiphospholipid syndrome. A person may test positive for one or more antiphospholipid antibodies without ever developing a blood clot or pregnancy-related complication. Such individuals do not necessarily require the same treatment as someone who has been diagnosed with APS. Doctors consider the antibody type, antibody levels, persistence of the antibodies, personal medical history and other risk factors when determining the appropriate approach.
Yes. APS is an autoimmune disorder in which the immune system produces antiphospholipid antibodies that can increase the risk of abnormal blood clotting.
There is currently no definitive cure that permanently eliminates the underlying autoimmune tendency. Treatment is aimed at preventing blood clots and managing complications.
Many people with APS can lead active and fulfilling lives with appropriate medical care. Long-term monitoring and treatment may be necessary, particularly for people who have previously experienced blood clots.
Yes. APS is associated with recurrent pregnancy loss and several other pregnancy complications. Appropriate treatment and specialist monitoring can improve pregnancy outcomes in many affected women.
Medical Disclaimer: This article is intended for general educational purposes and should not be considered a substitute for professional medical advice, diagnosis or treatment. If you have symptoms of a blood clot, stroke or another medical emergency, seek immediate medical attention. Treatment decisions, particularly regarding anticoagulant medicines and pregnancy, should be made by a qualified healthcare professional.
