Antiphospholipid syndrome

Learn about causes and treatment of this blood condition that mainly affects women and may cause blood clots and miscarriages.

Update Date: 19.09.2025

Overview
Symptoms
When to see a doctor
Causes
Risk factors
Complications
Diagnosis
Treatment
Self care
Preparing for your appointment

Overview

Antiphospholipid (AN-te-fos-fo-LIP-id) syndrome is a condition in which the immune system mistakenly makes 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 heart attack, stroke and other conditions. During pregnancy, antiphospholipid syndrome also can result in miscarriage and stillbirth. Some people who have the antibodies may not have any symptoms.

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

Symptoms

Symptoms of antiphospholipid syndrome can include:

  • Blood clots in the legs, also called deep vein thrombosis (DVT). Symptoms of DVT include pain, swelling and a change in skin color. These clots can travel to the lungs and cause a condition called pulmonary embolism.
  • Repeated miscarriages or stillbirths. Other complications of pregnancy include dangerously high blood pressure, called preeclampsia, and premature delivery.
  • Stroke. A stroke can occur in a young person who has antiphospholipid syndrome but no known risk factors for cardiovascular disease.
  • Transient ischemic attack (TIA). Similar to a stroke, a TIA usually lasts only a few minutes and causes no permanent damage.
  • Rash. Some people develop a rash with a lacy, netlike pattern.

Less common symptoms include:

  • Neurological symptoms. Chronic headaches, including migraines, as well as 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, also called thrombocytopenia. This decrease in blood cells needed for clotting can cause episodes of bleeding, particularly from the nose and gums. Bleeding into the skin can appear as patches of small, discolored spots.

When to see a doctor

Seek emergency care if you have symptoms of:

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

Contact your healthcare professional if you have any of the following signs and symptoms of serious bleeding:

  • Bleeding from the nose or gums that can't be explained.
  • A heavy menstrual period that is not usual.
  • Vomit that is bright red or looks like coffee grounds.
  • Black, tarry stool or bright red stool.
  • Abdominal pain with no explanation.

Causes

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 another condition, such as an autoimmune disease. You also can develop the syndrome without a known cause.

Risk factors

Antiphospholipid syndrome is more common in women than in men. Having another autoimmune condition, such as systemic lupus erythematosus or other connective tissue diseases, increases the risk of antiphospholipid syndrome.

It's possible to have the antibodies linked to antiphospholipid syndrome without getting symptoms. But having these antibodies increases your risk of having blood clots, particularly if you:

  • Become pregnant.
  • Are not mobile for a time, such as being on bed rest or sitting during a long flight.
  • Have surgery.
  • Smoke cigarettes.
  • Take contraceptives by mouth or take estrogen therapy for menopause.
  • Have high cholesterol and triglyceride levels.

Complications

Complications of antiphospholipid syndrome can include:

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

Rarely, severe antiphospholipid syndrome can cause damage to multiple organs in a short time.

Diagnosis

If you've had episodes of blood clots or pregnancy loss that aren't explained by known health conditions, talk with your healthcare professional. The health professional 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 have symptoms. A diagnosis of antiphospholipid syndrome is made only when these antibodies cause health problems.

Treatment

If you have blood clots, the standard first treatment is a combination of blood-thinning medicines. The most common are heparin and warfarin (Jantoven). Heparin is fast acting and delivered via shots, also called injections. Warfarin comes in pill form and takes several days to have an effect. Aspirin also is a blood thinner used to prevent blood clots.

When you're taking blood thinners, you have an increased risk of bleeding episodes. Your healthcare team monitors your dosage with blood tests. This monitoring can help make sure your blood can clot well enough to stop the bleeding of a cut or the bleeding under the skin from a bruise.

There is some evidence that other medicines might be helpful in treating antiphospholipid syndrome. These include hydroxychloroquine (Plaquenil), rituximab (Rituxan), eculizumab (Soliris) and medicines called 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 often 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 may be other steps you can take to protect your health. If you take blood-thinning medicines, 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 birth control or menopause symptoms.

Food and dietary supplements

Certain foods and medicines may affect how well your blood thinners work. Ask your healthcare professional for guidance about:

  • Safe food 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 healthcare professional if you need to limit or avoid alcohol.
  • Safe medicines and dietary supplements. Certain medicines, vitamins and herbal products can interact dangerously with warfarin. These include some pain relievers, cold medicines, upset stomach remedies and multivitamins, as well as garlic, ginkgo and green tea.

Preparing for your appointment

Complications of antiphospholipid syndrome — such as DVT, stroke or pregnancy loss — may 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 restrictions before your appointment. When you make the appointment, ask if there's anything you need to do in advance.

Make a list of:

  • Your 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 your family medical history. Tell your health professional about any relatives — such as parents, grandparents or cousins — who have had antiphospholipid syndrome.
  • All medicines, vitamins and other supplements you take, including doses.
  • Questions to ask your healthcare professional.

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 healthcare professional 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 healthcare professional is likely to ask you a number of questions, including:

  • Do you have a history of stroke 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 disease?
  • 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 discolored, netlike rash on your wrists or knees?
  • Do you smoke?

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