Antiphospholipid syndrome (APS): symptoms, diagnosis, treatment and pregnancy

The NHS says the main symptom of APS is a blood clot. Symptoms of a clot can include throbbing pain and swelling in one leg, usually the calf or thigh, pain and swelling in an arm or the tummy, warm, red or darkened skin around the painful area, and swollen veins that are hard or sore to touch. Sudden breathing difficulties, chest pain and coughing up blood can be signs of a pulmonary embolism.

Other symptoms the NHS lists include joint pain, bleeding or bruising more easily than other people, a reddish-blue lace-like rash on the lower legs, and repeated miscarriages. APS Support UK adds lower-grade symptoms such as headaches and migraines, memory problems, dizziness, cognitive difficulties and fatigue, and stresses that it is not necessary to have all symptoms to be diagnosed.

• Call 999 or go to A&E if you have severe difficulty breathing, pain in the chest or upper back, a very fast heartbeat, or someone has passed out. The NHS says these could be signs of a pulmonary embolism.

• Ask for an urgent GP appointment or call NHS 111 if you think you have a blood clot.

• Do not drive yourself to A&E; ask someone to drive you or call 999.

Antiphospholipid syndrome (APS) is an autoimmune condition. The NHS explains that the immune system attacks proteins in the blood, which makes the blood clot more easily. APS Support UK describes an overactive immune system producing antiphospholipid antibodies that cause the blood to clot too quickly in veins and arteries.

Because blood flows through the whole body, clots can affect any vein, artery or organ. APS Support UK describes two main types: primary APS, which develops in isolation, and secondary APS, which develops alongside another autoimmune disorder, usually lupus.

APS Support UK also notes that some people have antiphospholipid antibodies in their blood but never develop clots, pregnancy complications or symptoms, and that the reasons for this are not yet known.

The NHS says there is no cure for APS, but treatment can prevent future blood clots. You will usually be given warfarin, an anticoagulant. Most people need to keep taking warfarin for the rest of their lives because the risk of another clot remains high. You may also need treatment for other clot risk factors, such as high blood pressure or high cholesterol.

APS Support UK says the most commonly used drugs are aspirin, heparin and warfarin, with clopidogrel as an alternative to aspirin, and that newer anticoagulants such as rivaroxaban are being used for some people with venous clots. Which treatment is right depends on your history and is decided with a specialist.

The NHS stresses an important point: speak to your doctor before any medical procedure or before starting new medicines, including contraception, because some medicines may not be safe and extra monitoring may be needed.

The NHS lists pre-eclampsia, repeated miscarriages and premature birth among the complications of APS, and says treatment to prevent blood clots reduces the risk of these complications. APS Support UK states that APS is the most common potentially treatable cause of recurrent miscarriage and that with treatment women have a far better chance of a successful pregnancy than before diagnosis.

If you have APS, or have had pregnancy losses or clots, it is sensible to plan pregnancy with a specialist team so medicines can be reviewed before conception.

APS Support UK says that it is not known why people develop APS. The NHS notes that it is more common in women and in people with another autoimmune condition, such as lupus.

APS Support UK reports that one population-based study found a prevalence of about 1 in 2,000, making it a rare disease, although it believes the condition is under-recognised. It can affect people of any age, but most patients are diagnosed between the ages of 20 and 50, and for every two men affected, seven women are.

The NHS says you may be offered a test if you have had a blood clot and it is not obvious why, or if you have had 3 or more miscarriages. Diagnosis needs 2 blood tests, 3 months apart. Other tests, such as an ultrasound, CT scan or MRI scan, may be used to look for clots.

APS Support UK explains that diagnosis is usually made from a combination of a positive blood test and symptoms. It suggests that people under 50 who have had a DVT, pulmonary embolism, TIA, stroke or heart attack, particularly more than once, or more than one miscarriage or late pregnancy loss, should discuss with their doctor whether testing is appropriate. If APS is diagnosed you will likely be referred to a haematologist or rheumatologist.

The NHS says there are things you can do to reduce the risk of a blood clot if you have APS. It suggests getting regular exercise, eating a balanced diet, trying to keep to a healthy weight, drinking plenty of water to avoid dehydration (you are more likely to get a clot if you are dehydrated), and wearing flight stockings or socks to improve blood flow on long flights. A pharmacist can advise about flight stockings.

It advises not smoking, not drinking lots of alcohol, because this can make you dehydrated, and not sitting for long periods without moving, if you can avoid it. The NHS also says to speak to your doctor before having any medical procedures or starting any new medicines, including contraception, because some medicines may not be safe for you and you may need extra treatment or monitoring.

The sources used for this page do not give specific food rules. If you take warfarin, your anticoagulant clinic or pharmacist will explain what to know about food and other medicines.

APS Support UK says that although there is currently no cure, the outlook for many patients is very positive, particularly for those diagnosed early and treated appropriately. It says that with the correct treatment and lifestyle changes the majority of patients can lead a relatively normal life provided they continue with their medication, but that a small number continue to experience blood clots despite extensive treatment, for reasons that are not known.

In pregnancy, APS Support UK says treatment now means women have a 70% chance of a successful birth compared with just 20% before diagnosis. The NHS says APS increases the risk of deep vein thrombosis or pulmonary embolism, stroke or transient ischaemic attack, heart attack and pregnancy complications, which is why preventive treatment matters.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you think you have a blood clot. Call 999 or go to A&E now if you have severe difficulty breathing, pain in your chest or upper back, a very fast heartbeat, or someone has passed out. These could be signs of a pulmonary embolism or another serious condition that could be life-threatening.

The NHS says not to drive to A&E: ask someone to drive you or call 999 and ask for an ambulance, and bring any medicines you take with you.

APS Support UK says that if your doctor makes a diagnosis based on a positive blood test and symptoms, you will likely be referred to a specialist, either a haematologist or a rheumatologist, depending on the hospital, and that most early pregnancy units have a specialist to treat women with APS.

You can ask for referral through the NHS or choose to see a specialist privately. Either way, the NHS says to speak to your doctor before any procedure or new medicine, so make sure any private clinician knows your diagnosis and shares results with your GP.