Antiphospholipid syndrome


Antiphospholipid (AN-te-fos-fo-LIP-id) syndrome is a condition in which the immune system mistakenly creates antibodies that attack tissues in the body. These antibodies can cause blood clots to form in arteries and veins.

Blood clots can form in the legs, lungs and other organs, such as the kidneys and spleen. The clots can lead to a heart attack, strokes and other conditions. During pregnancy, antiphospholipid syndrome also can result in miscarriage and stillbirth. Some people who have the syndrome have no signs or symptoms.

There's no cure for this uncommon condition, but medications can reduce the risk of blood clots and miscarriage.


Signs and symptoms of antiphospholipid syndrome can include:

  • Blood clots in legs (DVT). Signs of a DVT include pain, swelling and redness. These clots can travel to the lungs (pulmonary embolism).
  • Repeated miscarriages or stillbirths. Other complications of pregnancy include dangerously high blood pressure (preeclampsia) and premature delivery.
  • Stroke. A stroke can occur in a young person who has antiphospholipid syndrome but no known risk factors for cardiovascular diseases.
  • Transient ischemic attack (TIA). Similar to a stroke, a usually lasts only a few minutes and causes no permanent damage.
  • Rash. Some people develop a red rash with a lacy, net-like pattern.

Less common signs and symptoms include:

  • Neurological symptoms. Chronic headaches, including migraines; dementia and seizures are possible when a blood clot blocks blood flow to parts of the brain.
  • Cardiovascular disease. Antiphospholipid syndrome can damage heart valves.
  • Low blood platelet counts (thrombocytopenia). This decrease in blood cells needed for clotting can cause episodes of bleeding, particularly from the nose and gums. Bleeding into the skin will appear as patches of small red spots.

When to see a doctor

Contact your health care provider if you have unexplained bleeding from your nose or gums; an unusually heavy menstrual period; vomit that is bright red or looks like coffee grounds; black, tarry stool or bright red stool; or unexplained abdominal pain.

Seek emergency care if you have signs and symptoms of:

  • Stroke. A clot in your brain can cause sudden numbness, weakness or paralysis of your face, arm or leg. You may have difficulty speaking or understanding speech, visual disturbances and a severe headache.
  • Pulmonary embolism. If a clot lodges in your lung, you may experience sudden shortness of breath, chest pain and coughing up blood-streaked mucus.
  • Deep vein thrombosis (DVT). Signs and symptoms of DVTs include swelling, redness, or pain in a leg or arm.


Antiphospholipid syndrome occurs when the immune system mistakenly produces antibodies that make blood much more likely to clot. Antibodies usually protect the body against invaders, such as viruses and bacteria.

Antiphospholipid syndrome can be caused by an underlying condition, such as an autoimmune disorder. You can also develop the syndrome without an underlying cause.

Risk factors

Antiphospholipid syndrome is more common in women than in men. Having another autoimmune condition, such as lupus, increases the risk of antiphospholipid syndrome.

It's possible to have the antibodies associated with antiphospholipid syndrome without developing signs or symptoms. However, having these antibodies increases your risk of developing blood clots, particularly if you:

  • Become pregnant
  • Are immobile for a time, such as being on bed rest or sitting during a long flight
  • Have surgery
  • Smoke cigarettes
  • Take oral contraceptives or estrogen therapy for menopause
  • Have high cholesterol and triglycerides levels


Complications of antiphospholipid syndrome can include:

  • Kidney failure. This can result from decreased blood flow to your kidneys.
  • Stroke. Decreased blood flow to a part of your brain can cause a stroke, which can result in permanent neurological damage, such as partial paralysis and loss of speech.
  • Cardiovascular problems. A blood clot in your leg can damage the valves in the veins, which keep blood flowing to your heart. This can result in chronic swelling and discoloration in your lower legs. Another possible complication is heart damage.
  • Lung problems. These can include high blood pressure in your lungs and pulmonary embolism.
  • Pregnancy complications. These can include miscarriages, stillbirths, premature delivery, slow fetal growth and dangerously high blood pressure during pregnancy (preeclampsia).

Rarely, in severe cases, antiphospholipid syndrome can lead to multiple organ damage in a short time.


If you've had episodes of blood clots or pregnancy loss that aren't explained by known health conditions, your health care provider can schedule blood tests to check for clotting and for the presence of the antibodies associated with antiphospholipid syndrome.

To confirm a diagnosis of antiphospholipid syndrome, the antibodies must appear in your blood at least twice, in tests conducted 12 or more weeks apart.

You can have antiphospholipid antibodies and never develop signs or symptoms. A diagnosis of antiphospholipid syndrome is made only when these antibodies cause health problems.


If you have blood clots, standard initial treatment involves a combination of blood-thinning medications. The most common are heparin and warfarin (Jantoven). Heparin is fast-acting and delivered via injections. Warfarin comes in pill form and takes several days to take effect. Aspirin is also a blood thinner.

When you're taking blood thinners, you have an increased risk of bleeding episodes. Your doctor will monitor your dosage with blood tests to be sure your blood is capable of clotting enough to stop the bleeding of a cut or the bleeding under the skin from a bruise.

There is some evidence that other drugs might be helpful in treating antiphospholipid syndrome. These include hydroxychloroquine (Plaquenil), rituximab (Rituxan) and statins. More study is needed.

Treatment during pregnancy

It's possible to have a successful pregnancy if you have antiphospholipid syndrome, especially with treatment. Treatment usually involves heparin or heparin with aspirin. Warfarin isn't given to pregnant women because it can affect the fetus.

Self care

Depending on your treatment plan for antiphospholipid syndrome, there are other steps you can take to protect your health. If you take blood-thinning medications, take extra care to keep from injuring yourself and to avoid bleeding.

  • Avoid contact sports or other activities that could cause bruising or injury or cause you to fall.
  • Use a soft toothbrush and waxed floss.
  • Shave with an electric razor.
  • Take extra care when using knives, scissors and other sharp tools.
  • Women should avoid using estrogen therapy for contraception or menopause.

Food and dietary supplements

Certain foods and medications may affect how well your blood thinners work. Ask your health care provider for guidance about:

  • Safe dietary choices. Vitamin K can lessen the effectiveness of warfarin, but not other blood-thinners. You might need to avoid eating large amounts of vitamin K-rich foods such as avocado, broccoli, Brussels sprouts, cabbage, leafy greens and garbanzo beans. Alcohol can increase warfarin's blood-thinning effect. Ask your doctor if you need to limit or avoid alcohol.
  • Safe medications and dietary supplements. Certain medications, vitamins and herbal products can interact dangerously with warfarin. These include some pain relievers, cold medicines, stomach remedies or multivitamins, as well as garlic, ginkgo and green tea.

Preparing for your appointment

In most cases, complications of antiphospholipid syndrome — such as DVT, stroke or pregnancy loss — will prompt you to seek medical care. Depending on your complication, you'll likely see a specialist in vascular disease, obstetrics or hematology.

Here's some information to help you get ready for your appointment.

What you can do

Be aware of any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do in advance. Make a list of:

  • Your signs or symptoms and when they began
  • Key personal information, including major recent events or changes in your life
  • Key medical information, including other conditions or infections you have and family medical history, especially close relatives who've had antiphospholipid syndrome
  • All medications, vitamins and other supplements you take, including doses
  • Questions to ask your doctor

Take a family member or friend along, if possible, to help you remember the information you get.

For antiphospholipid syndrome, some questions to ask your doctor include:

  • What's the most likely cause of my symptoms?
  • What tests do I need?
  • What treatment do you recommend?
  • How will we know if my treatment is working?
  • Does this condition increase my risk of other medical problems?
  • Does this condition increase my risk of health problems during pregnancy? Are there treatments to reduce that risk?
  • Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions, as well.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

  • Do you have a history of strokes or blood clots?
  • Do you have a history of pregnancy complications, such as high blood pressure, miscarriage or stillbirth?
  • Do you have lupus or another autoimmune disorder?
  • Have you ever been tested for sexually transmitted infections or chronic viral diseases, such as hepatitis?
  • Do you have frequent headaches?
  • Have you noticed a red, net-like rash on your wrists or knees?
  • Do you smoke?

Content From Mayo Clinic Updated: 02/24/2022
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