 |
 |
 |
 |
 |
 |
About thrombosis
Thrombophilia: acquired thrombophilia
Antiphospholipid or Hughes' syndrome
Antiphospholipid syndrome (APS) results from the presence of antiphospholipid antibodies in the blood, combined with a previous thrombosis, specific problems during pregnancy, or both. It is also known as Hughes' syndrome, after Dr Graham Hughes, who first described the condition in the British Medical Journal in 1983.
Hughes, GRV. Thrombosis,
abortion, cerebral disease and lupus anticoagulant. BMJ 1983;
287: 1088-9.
APS and thrombosis
Unlike the other thrombophilias, which tend to cause venous
thrombosis, antiphospholipid antibodies can also lead to arterial
thrombosis or thrombosis in small blood vessels.
Once someone with APS has had a thrombosis, further thromboses tend to occur in the same area. For example, if an individual has had a stroke, they will tend to have further strokes; if they have had a deep vein thrombosis, they will tend to have further DVT.
Antiphospholipid antibodies appear to affect the brain in particular and are a likely cause of strokes in younger people.
APS and pregnancy
Many women with antiphospholipid antibodies do not have any problems during
pregnancy. However some women with antiphospholipid antibodies may have a
miscarriage during the first 12 weeks. This is because the antibodies inhibit
the growth of the early foetal cells.
In some pregnant women antiphospholipid antibodies can cause thrombosis in the small and delicate blood vessels of the placenta. The placenta is then unable to supply the foetus with enough nutrition, so the foetus may stop growing and may die in extreme cases. Sometimes damage to the placenta prevents the foetus growing to normal size, so the baby is small at birth. This is known as intrauterine growth restriction.
In other cases the damaged placenta may lead to pre-eclampsia in the mother. Pre-eclampsia during pregnancy is a potentially dangerous condition, resulting in swelling, leaky kidneys and high blood pressure.
The best way of predicting how well a pregnancy will progress is by looking at what has happened before. If a woman with antiphospholipid antibodies has previously had a normal pregnancy, then it is likely that she will do so again.
One area requiring further research is to find a way of predicting whether women with antiphospholipid syndrome who are planning their first pregnancy will have any problems, and if so, what sort of problems are likely.
Other problems related to APS
A number of other symptoms may be seen in individuals with APS.
These include:
Blotchy skin (livedo reticularis)
About 10 per cent of individuals with APS have a type of skin blotchiness,
known as livedo reticularis. This may be in the form of blue knees,
or purplish vein colouration on the back of the wrists. It is useful in making
a diagnosis in some cases.
Thrombocytopenia
In a small percentage of people with antiphospholipid antibodies, the blood
platelet numbers are reduced below the normal range. This is known as thrombocytopenia.
The decrease in platelet count does not usually cause any problems, other
than a tendency to bruise easily. It is very rare for platelet counts to fall
to dangerously low levels.
Systemic lupus erythematosus
Some individuals with APS may also have systemic lupus erythematosus,
or Lupus. Lupus affects many thousands of people, particularly women. It is
a disorder of the immune system, causing an overproduction of antibodies.
This results in a complex illness that includes fatigue, rashes, joint pains
and in some cases, potentially life-threatening kidney and brain disease.
Evidence suggests that very few individuals with APS go on to develop more generalised lupus. People with APS who do not have lupus outnumber those with the disease. When APS alone is present it is known as primary APS. When it occurs with systemic lupus erythematosus it is known as secondary APS.
Tests for antiphospholipid antibodies
Tests for antiphospholipid antibodies are usually carried out as part of a
thrombophilia screen. These include two main tests: anticardiolipin antibodies
and the confusingly named lupus anticoagulant. The lupus anticoagulant
is a double misnomer, as it is neither a test for lupus, nor is it a test
for an anticoagulant.
There are major differences between the two tests and some people may show a positive result for one, but not the other. Therefore both tests must be performed, to ensure a diagnosis is made.
Based on the test results, an individual's anticardiolipin
levels are generally expressed as low, medium or high. However this level
is not necessarily an accurate indicator of risk, as some individuals with
high anticardiolipin levels never suffer any medical problems, while others
with low or medium levels have full APS.
Treatment of APS
As for other thrombophilias, treatment for APS involves giving anticoagulant
drugs to prevent the antibodies from causing further thrombosis. The three
drugs commonly used are aspirin, warfarin and low molecular weight heparin.
Aspirin is given in small doses, such as 75-100mg daily
(one quarter aspirin or 'baby aspirin'). It has long been established that
aspirin thins the blood by reducing the function of platelets. In cases of
recurrent miscarriage, for example, giving aspirin alone has dramatically
improved success rates.
If someone has already had a thrombosis, then aspirin is not strong enough
to prevent a recurrence. In this case warfarin is usually given. Warfarin
(Coumadin) is an anticoagulant drug, used worldwide
as a blood-thinning agent. For example, most people with a deep vein thrombosis
in the leg are given warfarin for six months.
For those with APS, it is usually recommended that warfarin treatment is indefinite and that the blood thinness level is kept higher than for most other conditions. The INR (international normalised ratio) measure of blood thinness for people with APS is kept at 3-4 when they have had a stroke or arterial problem, whereas for patients with other thrombotic risks it tends to be kept at 2-3.
Heparin is usually given to people with APS before
and after surgery and during pregnancy. This is because its anticoagulant
effects, unlike those of warfarin, can be easily reversed. Also heparin can
be used safely throughout pregnancy, whereas warfarin can affect the developing
foetus, especially if taken during the first 12 weeks.
Copyright
© Lifeblood: The Thrombosis Charity 2003-2006. A
company limited by guarantee. Registered Company No: 4354472.
Registered Charity No: 1090540
