Living with an autoimmune condition like lupus can make you more likely to develop other immune conditions like antiphospholipid syndrome (APS).

APS causes the body to form blood clots more easily than normal. While it can affect anyone, it’s commonly diagnosed in people with lupus.

In this article, we cover everything you need to know about antiphospholipid syndrome, including what it is, its most common symptoms, possible triggers, and how to treat it.

Here’s what you need to know.

What is antiphospholipid syndrome (APS)?

Antiphospholipid syndrome (APS) is an autoimmune condition that makes the body more likely to form blood clots. People with the condition have antiphospholipid antibodies, which are associated with an increased risk of abnormal blood clotting.

The immune system is meant to act as a protective barrier against potentially dangerous pathogens that enter the body. Immune cells create antibodies—proteins specifically designed to target, attack, and kill specific foreign pathogens.

With APS, the immune system misfires, making abnormal antibodies. These APS antibodies react with proteins involved in normal blood clotting processes. This can increase the risk of blood clots forming in the veins or arteries.

The three antibodies associated with APS are:

• Lupus anticoagulant
• Anticardiolipin
• Anti-B2 glycoprotein 1

APS antibodies are more common in people with systemic lupus (SLE). Research suggests that around 30% of people with lupus have these antibodies, although not everyone will develop APS symptoms or blood clots.

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Forms of APS

There are three primary forms of APS.

Type of APS: Description

Thrombotic APS: Defined by the presence of blood clots in the veins or arteries. The most common type of blood clot in people with thrombotic APS is a deep vein thrombosis (DVT).

Obstetric APS: Pregnancy-related complications linked to APS, including recurrent miscarriage, pre-eclampsia, placental problems, or premature birth.

Catastrophic APS: Rapid development of blood clots across multiple organs and blood vessels. This condition can be life-threatening and requires urgent medical treatment.

Symptoms of antiphospholipid syndrome

APS increases the risk of blood clots forming in the veins and arteries. The type and severity of symptoms depend on where the blood clot forms or gets stuck.

While blood clots often develop in the deep veins of the legs, APS-related clots can affect many different veins and arteries throughout the body.

Here are some of the most common symptoms of a blood clot in a limb:

• Swelling
• Pain and tenderness
• Heat
• Redness

In more severe cases, blood clots can impact the heart, lungs, or brain. Symptoms to watch for include:

• Difficulty breathing
• Fast or irregular heartbeat
• Chest pain that gets worse when you breathe deeply
• Cough
• Fainting
• Dizziness
• Sudden weakness or numbness
• Changes in speech

Important note: Blood clots can cause life-threatening complications such as stroke, heart attack, or pulmonary embolism. If you think you or someone else has a blood clot anywhere in the body, call the emergency services immediately. 

How APS is diagnosed

It is not known exactly what causes APS. Most people diagnosed with the condition only learn they have it after experiencing a blood clot or pregnancy complication.

If you have experienced a blood clot or pregnancy loss without a clear cause, or you have recently been diagnosed with an autoimmune condition like lupus, it’s worth asking your doctor about testing for antiphospholipid antibodies.

Your doctor will check your blood work for at least one of the three primary antibodies associated with the condition. A diagnosis of APS is usually based on both antibody test results and a history of related symptoms or complications, such as blood clots or certain pregnancy difficulties.

Antiphospholipid syndrome treatment options

There is no known cure for APS. Treatment is focused on reducing the risk of blood clots and their complications with anticoagulant medications.

If you are not pregnant, your doctor may prescribe:

• Heparin: Taken intravenously through an IV, this medication is primarily used to break up blood clots. This is a common treatment option in hospital settings.

• Warfarin: Warfarin is an oral anticoagulant medication that makes it harder for your blood to form clots. It can be taken over long periods to manage APS.

• Aspirin: Over-the-counter oral aspirin medication has anticoagulant properties that can help reduce your risk of blood clots. Do not start taking aspirin therapy for blood clots without first consulting your doctor.

If you are pregnant or planning a pregnancy, your doctor may recommend the following medications:

• Enoxaparin: A pregnancy-safe blood-thinning medication (anticoagulant) that can help reduce the risk of APS-related pregnancy complications. It’s given as an injection.

• Corticosteroids: Oral corticosteroids can help suppress the immune system and make blood clots less likely. 

Important note: Blood-thinning medications can have serious side effects. Monitor closely for side effects, including multiple nose bleeds, blood in your stool, vomiting blood, or changes to your vision. If you are affected by any of these, seek medical care.

Get a full picture of your health

APS can have serious effects, so your doctor will want to monitor you closely over time—especially if you also have lupus or another autoimmune condition

Keeping track of symptoms, medications, and changes in your health can help you prepare for appointments and support more informed conversations with your healthcare team.

The Human Health app lets you log everything in one place, so you have organized records to share with your doctor.

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Frequently asked questions

What is the life expectancy for someone with APS?

In many cases, APS does not directly impact life expectancy, particularly when the condition is diagnosed early and managed effectively. However, severe complications related to blood clots can be life-threatening.

Following your treatment plan, taking medications as prescribed, and attending regular medical follow-up appointments can help reduce the risk of serious complications.

What are the risk factors of developing APS?

Anyone can develop APS, but some factors increase your risk.

These include being born female, being aged between 3 and 40 years, having an autoimmune condition like lupus or rheumatoid arthritis, and having a bacterial or viral infection like HIV or hepatitis C.

What is catastrophic antiphospholipid syndrome?

Catastrophic antiphospholipid syndrome (CAPS) is a rare, life-threatening form of APS that is characterized by the formation of multiple-organ clots. This is called a thrombotic storm.

Several things can trigger CAPS, including surgery, medication, or cancer. It has a very high mortality rate.

What triggers antiphospholipid syndrome?

There is no definitive list of APS triggers. However, pregnancy, prolonged periods of immobility, surgery, smoking, taking oral hormonal contraceptives, and high cholesterol levels are all associated with increased blood clot risk.

Disclaimer: Human Health is a health tracking platform and does not provide medical advice, diagnosis, or treatment. The information in this guide is for educational purposes only and is not a substitute for professional medical care. Always consult your doctor or healthcare provider with questions about your health.

Sources:

1. Antiphospholipid Syndrome (2024)
2. About antiphospholipid syndrome, The National Human Genome Research Institute
3. Antiphospholipid antibodies, Johns Hopkins Lupus Center
4. Forecasting the Future of Antiphospholipid Syndrome: Prospects and Challenges (2023)
5. About venous thromboembolism (blood clots), The Centers for Disease Control and Prevention
6. Antiphospholipid antibody syndrome, Thrombosis Canada
7. Antiphospholipid syndrome, Cleveland Clinic
8. Antiphospholipid syndrome (APS), The National Heart, Lung, and Blood Institute
9. Catastrophic Antiphospholipid Syndrome: A Life-Threatening Condition (2024)
10. Antiphospholipid syndrome, Mayo Clinic