Antiphospholipid Syndrome


What is antiphospholipid syndrome?

Antiphospholipid syndrome (also known as APS, antiphospholipid antibody syndrome or Hughes syndrome) is an autoimmune disorder in which your body’s immune system attacks proteins bound to phospholipids, a certain kind of fat found in all of the cells in your body. These antibodies make it much more likely that you will have blood clots in your arteries or veins, miscarriages and/or other pregnancy complications, such as preeclampsia.

How does antiphospholipid syndrome cause blood clots?

If you have antiphospholipid syndrome, your immune system makes abnormal proteins called antiphospholipid antibodies in your blood. When the antibodies attack your phospholipids, cells can get damaged. This damage can contribute to the formation of blood clots in your arteries and veins. The cause of increased risk of blood clots for people who have antiphospholipid antibodies is not straight-forward and there are likely multiple factors involved. Some people have antiphospholipid antibodies but never have signs or symptoms of the antiphospholipid syndrome.

How does antiphospholipid syndrome cause miscarriages?

Healthcare researchers believe that small blood clots get stuck in the placenta of individuals who are pregnant and have antiphospholipid syndrome. The blood clots block the flow of nutrients to the baby and can cause a miscarriage.

Who does antiphospholipid syndrome affect?

Antiphospholipid syndrome can affect anyone, but females are five times more likely to have antiphospholipid syndrome than males. Most individuals with antiphospholipid syndrome are diagnosed between the ages of 30 and 40.

How common is antiphospholipid syndrome?

While healthcare professionals and researchers don’t have exact numbers on the prevalence of the disorder, antiphospholipid syndrome is thought to be fairly common. Approximately 20% of people younger than 50 who have a stroke have antiphospholipid syndrome, and approximately 10% to 15% of individuals who experience recurrent miscarriages have antiphospholipid syndrome.

Symptoms and Causes

What are the symptoms of antiphospholipid syndrome?

Symptoms and signs of antiphospholipid syndrome can include:

  • Having blood clots.
  • Experiencing repeated (recurrent) miscarriages.
  • Having low blood platelet levels.
  • Having a shortage of red blood cells (anemia).
  • Having a lace-like reddish or purplish pattern on your skin (livedo reticularis).
  • Having heart valve abnormalities.

Antiphospholipid syndrome most commonly causes blood clots. The symptoms of having a blood clot depend on where the blood clot is in your body. Symptoms and signs of having blood clots can include:

  • Having chest pain and shortness of breath.
  • Experiencing pain, redness and swelling in your arm or leg.
  • Experiencing frequent headaches.
  • Experiencing discomfort in your arms, back, neck and/or jaw.
  • Abdominal pain.

It’s important to contact your healthcare provider immediately or go to the nearest hospital if you are experiencing signs and symptoms of a blood clot. Blood clots can be deadly.

What causes antiphospholipid syndrome?

Antiphospholipid syndrome is an autoimmune disorder. It develops when your body’s immune system mistakenly makes antibodies that attack phospholipid-binding proteins in your cells. Researchers are unsure what exactly causes your immune system to suddenly attack its own blood proteins, but healthcare professionals think it has to do with genetic mutations and environmental factors.

Diagnosis and Tests

How is antiphospholipid syndrome diagnosed?

Antiphospholipid syndrome is diagnosed through more than one blood test that checks for antiphospholipid antibodies. This test is usually only taken by people with blood clots and/or individuals who are experiencing recurrent (frequent) miscarriages. Some people can have antiphospholipid antibodies and never experience a blood clot.

The screening for antiphospholipid syndrome requires three kinds of blood tests to check for antiphospholipid antibodies. Each individual test cannot find all of the possible antibodies, so the tests are often all used together. At least one of the three types of blood tests must be positive two different times three months or more apart in order for the person to be diagnosed with antiphospholipid syndrome.

Some people have antiphospholipid antibodies but never have signs or symptoms of the syndrome. Just because you have the antibodies doesn't mean that you have antiphospholipid syndrome. To be diagnosed with antiphospholipid syndrome (APS), you must have APS antibodies in addition to a history of health problems related to the disorder, such as blood clots and/or frequent miscarriages.

Management and Treatment

How is antiphospholipid syndrome treated?

The main goal of treatment for antiphospholipid syndrome is to prevent further episodes of the medical conditions it is causing, whether that’s blood clots and/or miscarriages.

Blood thinners (anticoagulants) are generally used to prevent blood clots. Blood thinner medications that people with antiphospholipid syndrome may use include:

  • IV heparin: If an individual is experiencing an acute blood clot, they will be given an IV of heparin, an anticoagulant, in the hospital.
  • Oral warfarin (Coumadin): This blood thinner is a pill that is taken to prevent blood clots. People who have antiphospholipid syndrome often need to take an oral blood thinner for long periods of time.
  • Aspirin: People with antiphospholipid syndrome who have had a blood clot in an artery may take aspirin, which can help prevent blood clots.

Individuals who have experienced recurrent miscarriages and who have been diagnosed with antiphospholipid syndrome may take the following medications to prevent another miscarriage and to deliver a healthy baby:

  • Enoxaparin injections and low-dose aspirin: Enoxaparin shots and low-dose aspirin are the standard treatment for preventing miscarriages for people who have antiphospholipid syndrome. The combination therapy starts at the beginning of the pregnancy and continues in the period immediately after the delivery of the baby.
  • IV immunoglobulin infusions: In more difficult cases of recurrent miscarriage, IV immunoglobulin infusions might be used. Immunoglobulin infusions are used to treat immune system disorders.
  • Corticosteroids (prednisone): In more difficult cases of recurrent miscarriage, corticosteroids such as prednisone or prednisolone might be used.

Are there side effects of the medication used to prevent blood clots?

Taking blood thinners (anticoagulants) increases your chances of bleeding internally and externally. Your healthcare provider will check your dosage with blood tests to make sure your blood will be able to clot enough if you get a cut or a bruise.

It is important to know the warning signs of bleeding issues when you are taking blood thinners. Contact your healthcare provider right away if you experience any of the following symptoms:

  • Having unexplained bleeding from your gums and/or nose.
  • Having a heavier menstrual period than normal.
  • Having vomit that is bright red or looks like coffee grounds.
  • Experiencing bright red blood in your poop or having black, tarry poop.
  • Experiencing pain in your abdomen or severe head pain.
  • Experiencing sudden changes in your eyesight.
  • Experiencing a sudden loss of movement in your arms and/or legs.

Are the medications used to prevent miscarriages safe?

The treatment therapy of heparin and low-dose aspirin for pregnant people who have antiphospholipid syndrome is safe and effective for both the parent and the baby.

Is there a cure for antiphospholipid syndrome?

There is currently no cure for antiphospholipid syndrome. However, treatment in the form of medication can help prevent the medical conditions antiphospholipid syndrome can cause, including blood clots and miscarriages.

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What are the risk factors for antiphospholipid syndrome?

While researchers aren’t sure what exactly causes antiphospholipid syndrome, the following things are considered risk factors for developing it:

  • Being female: Approximately 70% of people who have antiphospholipid syndrome are female.
  • Having other autoimmune disorders: Approximately 30% to 40% of people who have lupus (systemic lupus erythematosus or SLE), an autoimmune disorder, have antiphospholipid syndrome.
  • Having a rheumatic disorder: Rheumatic disorders affect your joints, bones or muscles. People who have a rheumatic disorder are more likely to have antiphospholipid syndrome.
  • Having a family history of antiphospholipid syndrome: The syndrome sometimes runs in families.

Outlook / Prognosis

What is the prognosis (outlook) for antiphospholipid syndrome?

If people with antiphospholipid syndrome are taking medication for the disorder and are maintaining their overall health, they can generally live healthy lives. Blood thinners work well to treat antiphospholipid syndrome and to prevent blood clots. However, you will need to see your healthcare provider regularly if you are on blood thinners to make sure your blood is still able to clot properly if you get a cut or bruise. Most people with antiphospholipid syndrome need to be on medication to treat it for the rest of their lives.

With proper treatment, pregnant individuals who have antiphospholipid syndrome are more likely to carry babies to term than those whose antiphospholipid syndrome isn't treated.

Antiphospholipid syndrome can be fatal. Death may occur as a result of dangerous blood clots in the heart, lungs or brain that are caused by antiphospholipid syndrome. If you have been diagnosed with antiphospholipid syndrome, it's important to take your medication regularly to prevent blood clots from forming in your body. Go to the nearest hospital as soon as possible if you are experiencing signs and symptoms of a blood clot.

Can I die from antiphospholipid syndrome?

In very rare cases, people with antiphospholipid syndrome develop blood clots in multiple veins or arteries throughout their body. This is called catastrophic antiphospholipid syndrome (CAPS). CAPS usually affects and causes damage to the kidneys, lungs, brain, heart and/or liver. It leads to death in over half of the people who have CAPS. Less than 1% of people who have antiphospholipid syndrome develop catastrophic antiphospholipid syndrome.

Living With

How do I take care of myself if I have antiphospholipid syndrome?

The main goal for managing antiphospholipid syndrome is preventing blood clots. Blood clots can largely be prevented through the use of blood thinner medication. However, there are several other conditions that can increase your risk of developing blood clots. If you have been diagnosed with antiphospholipid syndrome, it is essential to prevent, avoid or properly manage the following risk factors for developing blood clots if they apply to you:

  • Diabetes: Having diabetes increases your likelihood of developing plaque buildup in your arteries, which can cause blood clots. It’s important to manage your diabetes well if you have antiphospholipid syndrome.
  • High blood pressure (hypertension): High blood pressure can cause blood clots to form in the arteries that lead to your brain, which could cause a stroke. It’s important to manage your blood pressure if you have antiphospholipid syndrome.
  • High cholesterol: High cholesterol can contribute to the formation of blood clots in your legs. It’s important to manage your cholesterol if you have antiphospholipid syndrome.
  • Obesity: Having obesity promotes a state of inflammation in your body that can contribute to blood clots forming. It’s important to try to maintain a healthy weight if you have antiphospholipid syndrome.
  • Smoking: Smoking increases your risk of developing blood clots and can damage blood vessels. If you have antiphospholipid syndrome and smoke, it is essential to stop smoking.
  • Estrogen therapy for menopause or birth control (contraception): Estrogen increases your risk of developing blood clots. Avoid using estrogen therapy if you have antiphospholipid syndrome. Talk to your healthcare provider about what will work best for you for birth control or menopause therapy.
  • Other autoimmune diseases or rheumatology disorders: If you have another autoimmune disease or rheumatology disorder, it is important to manage it as best as you can in order to be healthy and prevent blood clots.

When should I see my healthcare provider?

If you are taking a blood thinner (anticoagulant) to treat antiphospholipid syndrome, you will need to see your healthcare provider routinely to make sure your dosage is working well.

Antiphospholipid syndrome can increase the risk of pregnancy-related complications such as preeclampsia. Talk with your healthcare provider about how to manage your antiphospholipid syndrome if you're pregnant or planning on becoming pregnant.

When should I go to the emergency room?

If you are experiencing symptoms and signs of having a blood clot or if you are on a blood thinner and are experiencing extensive bleeding, go to the nearest hospital as soon as possible.

Frequently Asked Questions

Does having antiphospholipid syndrome (APS) mean I have lupus?

Although part of the testing for APS is called “lupus anticoagulant”, your healthcare provider is not specifically testing for lupus when ordering tests for APS. Some people with lupus also have APS, which is where this term originated.

A note from Cleveland Clinic

Getting a diagnosis can be scary. Know that your healthcare team is there to help you and answer your questions. Antiphospholipid syndrome is very treatable. If you have had a blood clot or a miscarriage and have antiphospholipid syndrome, medication works well to help prevent them from happening again. Be sure to see your healthcare provider regularly to manage your antiphospholipid syndrome, and go to the nearest hospital if you are experiencing symptoms of a blood clot.

Last reviewed by a Cleveland Clinic medical professional on 08/19/2021.


  • American College of Rheumatology. Antiphospholipid Syndrome. ( Accessed 8/19/2021.
  • MedlinePlus. Antiphospholipid Syndrome. (,a%20stroke%20have%20antiphospholipid%20syndrome) Accessed 8/19/2021.
  • National Heart, Lung, and Blood Institute. Antiphospholipid Antibody Syndrome. ( Accessed 8/19/2021.

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