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Overview - Antiphospholipid syndrome (APS)

Antiphospholipid syndrome, sometimes called Hughes syndrome or sticky blood syndrome, is a rare condition where your blood clots more easily. It's treated with medicines that help prevent blood clots.

Symptoms of antiphospholipid syndrome

The main symptom of antiphospholipid syndrome is a blood clot, which can happen anywhere in the body.

Symptoms of a blood clot can include:

  • throbbing pain and swelling in 1 leg, usually the calf or thigh (rarely in both legs)
  • pain and swelling in your arm or tummy
  • warm, red or darkened skin around the painful or swollen area – this may be harder to see on brown or black skin
  • swollen veins that are hard or sore when you touch them
  • sudden breathing difficulties, chest pain and coughing up blood

These could be symptoms of deep vein thrombosis (DVT) or a pulmonary embolism.

Other symptoms of antiphospholipid syndrome can include:

  • joint pain
  • bleeding more easily than other people – signs include bruising easily and bleeding gums
  • a reddish-blue, lace-like rash on your lower legs – this may be harder to see on black or brown skin
  • having repeated miscarriages

Urgent advice: Ask for an urgent GP appointment or get help from NHS 111 if you:

  • you think you have a blood clot

You can call 111 or get help from 111 online.

Immediate action required: Call 999 or go to A&E now if:

  • you have severe difficulty breathing
  • you feel pain in your chest or upper back
  • your heart is beating very fast
  • someone has passed out

These could be signs of a pulmonary embolism or another serious condition which could be life-threatening and needs treatment straight away.

Find your nearest A&E
Information:

Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.

Bring any medicines you take with you.

Causes of antiphospholipid syndrome

Antiphospholipid syndrome is an autoimmune condition, where your immune system attacks proteins in your blood, making your blood clot more easily.

Antiphospholipid syndrome is more common in women, and in people with another autoimmune condition, such as lupus.

How antiphospholipid syndrome is diagnosed

You may be offered a test to check for antiphospholipid syndrome if:

  • you had a blood clot and it's not obvious why you had it
  • you’ve had 3 or more miscarriages

You'll need to have 2 blood tests, 3 months apart, to confirm a diagnosis of antiphospholipid syndrome.

You may also need other tests, such as an ultrasound, CT scan or MRI scan, to check for blood clots.

Treatment for antiphospholipid syndrome

There's no cure for antiphospholipid syndrome, but treatment can help prevent future blood clots.

You'll usually be given warfarin, a medicine to reduce your risk of blood clots (anticoagulant medicine).

Most people with antiphospholipid syndrome need to keep taking warfarin for the rest of their lives, as there's a high risk of having another blood clot in the future.

You may also need treatment for other conditions that increase your risk of a blood clot, such as high blood pressure or high cholesterol.

Important

If you have antiphospholipid syndrome, speak to your doctor before having any medical procedures or starting any new medicines (including contraception).

Some medicines may not be safe for you, and you may need extra treatment or monitoring during medical procedures.

Things you can do to reduce the risk of blood clots

If you have antiphospholipid syndrome, there are things you can do reduce the risk of a blood clot.

Do

  • get regular exercise

  • eat a balanced diet

  • try to keep to a healthy weight

  • drink plenty of water to avoid dehydration – you're more likely to get a clot if you're dehydrated

  • wear flight stockings or socks to improve your blood flow on long flights – a pharmacist can advise you about this

Don’t

  • do not smoke

  • do not drink lots of alcohol – this can make you dehydrated

  • do not sit for long periods without moving, if you can avoid it

Complications of antiphospholipid syndrome

Antiphospholipid syndrome increases your risk of having a blood clot, which can cause many problems including:

Treatment to prevent blood clots (anticoagulant medicine) reduces the risk of these complications.

Page last reviewed: 06 March 2026
Next review due: 06 March 2029