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Antiphospholipid syndrome (APS)

8-minute read

If you or someone else is having trouble breathing, or if you have symptoms of stroke or heart attack, call triple zero (000) and ask for an ambulance.

Key facts

  • Antiphospholipid syndrome (APS) is a blood disorder cause by abnormal antibodies in the blood.
  • APS affects females more than males.
  • Symptoms include blood clots, chest pain, stroke and pregnancy complications.
  • Treatment involves blood-thinning medicines and lifestyle changes to reduce your clotting risk.

What is antiphospholipid syndrome (APS)?

Antiphospholipid syndrome (APS) is an autoimmune blood disorder. It puts you at greater risk of developing blood clots and/or difficulty becoming or staying pregnant.

Blood clots can cause serious problems, such as deep vein thrombosis (DVT) in the legs, or damage to organs, such as your kidneys, lungs or brain.

APS is sometimes called Hughes syndrome. It is more common in females than in males.

What causes APS?

APS happens when antibodies, proteins the body produces to fight infections, start attacking your body instead — this is called an autoimmune reaction.

There are a few different types of APS:

  • Primary APS — when you have the disorder with no underlying autoimmune disorder.
  • Secondary APS — when the disorder is caused by or occurs alongside another conditions, including:
  • Catastrophic APS (CAPS) — a rare but life-threatening type of APS. It is when there is widespread clotting (thrombosis) in your small blood vessels that causes failure of 3 or more organs in less than one week.

What are the symptoms of APS?

Symptoms will depend on the where blood clots form and/or travel to and lodge. Blood clots due to APS can cause:

Some people with APS will also have problems such as an abnormal heart valve or too few platelets in their blood, which can cause bleeding. Some may also develop headaches, seizures or purplish skin discolouration.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

How is APS diagnosed?

APS is diagnosed via blood tests that look at h ow the blood is clotting and whether there are any of the abnormal antibodies present.

Your doctor may check you for APS if you have multiple blood clots or miscarriages that can't be explained by something else.

How is APS treated?

Not everyone who has abnormal antibodies will get blood clots. Because blood clots can be very serious, if you have APS, you may need to take medicine to thin your blood and reduce the chance of a clot.

The medicines most commonly used are heparin (an injection) and warfarin (a pill). Your doctor might also prescribe low-dose aspirin. Taking these medicines may increase your risk of bleeding, so your doctor will need to monitor you carefully.

If you are pregnant, you cannot take warfarin. Instead, your doctor may prescribe other medicines such as heparin or low dose aspirin. Taking blood thinning medicines can help maximise your chance of your carrying your baby to term.

If you have APS and are planning a pregnancy, it is best to talk to your doctor first about the risks and options available to you.

When should I see a doctor?

If you experience severe pain, shortness of breath or chest pain, call triple zero (000) and ask for an ambulance.

If you have been diagnosed with APS, see your doctor or seek emergency medical help if you have:

  • signs of a blood clot — pain, swelling, redness or tenderness in your arm or leg
  • signs of a miscarriage — spotting or bleeding if you are pregnant
  • signs of stroke — numbness or weakness in your face, arm or leg with speech or vision problems and dizziness
  • signs of pulmonary embolism — sudden shortness of breath, chest pain and coughing up mucus with blood in it
  • signs of gastrointestinal bleeding — unexplained bleeding from your nose or gums, a very heavy period, vomit with blood in it or black, tar-like faeces (poo)

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How can I prevent blood clots if I have APS?

If you have had a blood clot, you are at higher risk than others of having another one. Taking your medicine as prescribed will greatly lower your risk of developing a blood clot. You may have to stay on the medicine for the rest of your life, or until your doctor thinks the risks outweigh the benefits.

If you take blood-thinning medicine, you should try to avoid injuring yourself, to prevent major bleeding. Here are some other tips to reduce the chance of causing bleeding:

  • Use sharp tools or kitchen utensils with care.
  • Avoid contact sports.
  • Use a soft toothbrush, and not a hard one.
  • If you shave, use an electric shaver and not a blade razor.

Other things you can do to reduce your chance of developing blood clot include:

Some foods, medicines and supplements can interfere with blood thinning medicines. Ask your doctor what to avoid, and always let your doctor or pharmacist know that you take a blood thinning medicine.

Resources and support

Speak to your doctor if you have APS and you have concerns or questions. You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

You can find more information on APS on the Thrombosis Australia website.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: October 2023

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