Quick answer. Antiphospholipid syndrome (APS), also called “sticky blood” or Hughes syndrome, is an autoimmune condition in which the immune system makes antibodies that make the blood far more likely to clot. This leads to two main problems – dangerous blood clots (such as DVT, pulmonary embolism and stroke) and pregnancy complications including recurrent miscarriage – but with the right blood-thinning treatment, most people can manage the risks well.
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In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.
Know the emergency signs first: call 995 for sudden breathlessness or chest pain (possible clot on the lung), a painful swollen leg (possible DVT), or stroke signs – face drooping, arm weakness, speech difficulty (act F.A.S.T.).
What APS is and why blood “gets sticky”
APS is an autoimmune disorder: the immune system produces antiphospholipid antibodies that target proteins involved in blood clotting. The result is a tendency for the blood to clot too readily inside blood vessels – clots, not bleeding, are the core danger. They can form in veins, arteries, or the small vessels of the placenta during pregnancy. Because APS is an antibody-driven clotting problem, it is managed with medicines that thin the blood rather than surgery.
The two main problems: clots and pregnancy loss
- Blood clots – a clot in a deep leg vein is a DVT; a piece breaking off and lodging in the lungs is a pulmonary embolism; a clot affecting the brain can cause a stroke or transient ischaemic attack. Clots can also occur in less common sites;
- Pregnancy complications – APS is an important and treatable cause of recurrent miscarriage, particularly later (second-trimester) losses, as well as stillbirth, pre-eclampsia and problems with the baby’s growth from poor placental blood flow.
Primary vs secondary APS
APS can be primary (on its own) or secondary (alongside another autoimmune disease, most commonly lupus (SLE)). Because APS and lupus overlap, people diagnosed with one may be tested for the other. The distinction doesn’t usually change the core treatment (blood thinning) but affects the wider care a person needs.
Who is affected and how it shows up
APS is more common in women, which partly reflects its link with pregnancy complications and with lupus. It is often first suspected after an event rather than found on a routine test – typically an unexplained blood clot (especially in someone young or without obvious risk factors) or a pattern of recurrent miscarriages. Some people also notice a lacy, reddish-blue, net-like rash on the skin (livedo reticularis). Many people with the antibodies, however, remain well for long periods.
Catastrophic APS – the rare emergency
A very rare but severe form, catastrophic APS (CAPS), causes widespread clotting in multiple organs over a short period, which can rapidly threaten organ function and life. It requires immediate hospital treatment. Although uncommon, it is the reason APS is taken seriously and why sudden, severe symptoms should never be ignored.
How APS is diagnosed
Diagnosis combines a clinical history (a clotting event and/or defined pregnancy complications) with blood tests for antiphospholipid antibodies – lupus anticoagulant, anticardiolipin, and anti-beta-2 glycoprotein I. Crucially, the antibodies must be positive on two separate occasions at least 12 weeks apart, because a single positive test can be transient – for example after an infection – and does not by itself confirm APS. People positive for all three antibody types (“triple positive”) are considered higher-risk, which influences treatment.
Living with APS day to day
Beyond medication, a few practical points help. If you take warfarin, keeping a steady, consistent diet (particularly of vitamin-K-rich green vegetables) and attending your regular blood tests helps keep the blood-thinning in the right range, and you should tell any doctor or dentist that you are on anticoagulation before procedures. Carrying medical-alert information is sensible in case of an emergency. Discuss contraception with your doctor, since oestrogen-containing options add to clot risk, and always plan pregnancies in advance so specialist care and the right treatment can be arranged from the very start.
How APS is treated and risks reduced
The aim is to prevent clots:
- After a clot, people usually need long-term anticoagulation, most often warfarin, with regular monitoring. Certain direct oral anticoagulants (DOACs) are generally not recommended for high-risk APS – particularly triple-positive or arterial-clot APS – because studies found more clots on a DOAC than on warfarin. The choice of blood thinner should always be made by a specialist;
- In pregnancy, warfarin is avoided; instead, low-dose aspirin combined with heparin injections, under specialist obstetric and rheumatology care, substantially improves the chance of a successful pregnancy;
- Reducing other clot risk factors – stopping smoking, staying active, and being cautious with oestrogen-containing medicines such as the combined contraceptive pill;
- Pregnancy planning – anyone with APS hoping to conceive should arrange specialist care before pregnancy.
See a doctor if you’ve had an unexplained clot or recurrent miscarriages; a rheumatologist and, for pregnancy, an obstetric team coordinate care. Call 995 for the emergency signs above.
Related autoimmune & rheumatology topics
- Autoimmune disease (overview)
- Scleroderma
- Lupus nephritis
- Polymyositis & dermatomyositis
- Juvenile idiopathic arthritis
- Pseudogout (CPPD)
- Joint hypermobility
- Autoimmune hepatitis
- Behcet’s disease
- Lupus (SLE)
- Rheumatoid arthritis
- Rheumatologists in Singapore
Sources
- NHS — Antiphospholipid syndrome: sticky blood/Hughes syndrome, livedo reticularis, two tests ~3 months apart, warfarin, urgent-care advice.
- Mayo Clinic — 12-week retest rule, aspirin/heparin in pregnancy, warfarin avoidance in pregnancy.
- Tommy’s — recurrent miscarriage and aspirin-plus-heparin management.
- American Society of Hematology / TRAPS trial — antibody criteria; DOACs not recommended in high-risk (triple-positive) APS.