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Antiphospholipid Syndrome (APS)


Antiphospholipid syndrome (APS) is an autoimmune disorder in which your body's immune system (defense system) makes antibodies that attack the body’s cells, resulting in damage and inflammation. This can lead to the formation of blood clots in the veins and arteries of different organs, for example, legs, lungs, kidneys, etc. one significant consequence of APS is recurrent miscarriages that happen due to the formation of blood clots in the placenta, the organ that nurtures the fetus. Antiphospholipid syndrome is often treated with medicines that reduce the risk of clot formation as there is no cure for the disorder. 


The body’s defense system has been programmed to protect the body by producing special proteins called antibodies that attack foreign agents (bacteria and viruses). Due to some reasons, this programming gets disturbed, resulting in the production of antibodies that attack the body’s own cells, known as an autoimmune disease. A combination of genetic and environmental factors is thought to play a role in developing Antiphospholipid syndrome, although the exact cause is still unknown. In APS,  antibodies are produced against another protein present in the cell walls of different tissues and body organs, resulting in inflammation and the formation of clots. The clots make it difficult for the blood to flow fluently through the vessels resulting in the symptoms of the disease.


Antiphospholipid syndrome can be classified as primary or secondary.

When no other co-morbid or related disease cause APS, it is known as Primary Antiphospholipid Syndrome.

When APS is due to the presence of an underlying co-morbid or related disorder, it is known as Secondary Antiphospholipid Syndrome. For example, in SLE, antiphospholipid antibodies are also found and cause hypercoagulability.


APS is quite a common disorder and sometimes goes undiagnosed. It is believed that around 20% of people suffering a stroke and 10-15% of females experiencing miscarriages have an underlying APS disorder. In the USA, about 5 cases per 100,000 people are reported annually. Females are more likely to have the disorder, and the most common age of presentation is between 30 and 40 years. 

Risk Factors

Some of the risk factors that can increase the risk of developing the disorder include;

·         Genetic Markers: The presence of some typical genetic markers; HLA-DR4, HLA-DR7, and HLA-DRw53.

·         Race: Some races have more prevalence of APS, for example, Blacks, Hispanics, Asians, and Native Americans.

·         Gender: Female gender.

·         An underlying autoimmune disorder: The presence of another autoimmune disease like SLE or Rheumatoid arthritis increases the risk of developing APS.

·         Family history: A family member suffering from APS also makes you prone to having the disorder.

Signs And Symptoms

Signs and symptoms depend on the location of clots and the organ system involved. Platelets that help in the process of clotting are often consumed, resulting in low levels of platelets in the blood. Low levels of red blood cells (anemia) can be found too.

Clot formation in the legs: The presence of clots in the leg's veins causes a condition called Deep Venous Thrombosis, which can present with pain, redness, and swelling in the legs. These clots tend to reach the veins or arteries in the lungs leading to pulmonary embolism.

Pregnancy complications: Clots in the blood vessels of the placenta can cause recurrent miscarriages, stillbirth, pre-term birth, or pre-eclampsia, which is characterized by high blood pressure.

Nervous system: Symptoms involving clots in the brain include chronic headaches, migraines, and seizures. A big clot entirely or partially obstructing an artery can cause a stroke. A young person with a stroke should be evaluated for APS. A transient ischemic attack is similar to a stroke, but its duration is less than an hour, and no permanent damage ensues.

Skin: A net-like rash can appear on the skin in some people.

Heart: APS can result in damage to the heart valves.

Decreased platelet counts: Since platelets help in the clotting of the blood, reduced levels may cause bleeding episodes from the nose and gums.  Small blood spots on the skin may also form where bleeding occurs in the skin. 


If you experience the symptoms described above, you need to contact your health care provider. They will obtain a detailed history, including questions regarding your symptoms, recurrence, past medical history, family history, etc. After performing a physical examination, you may be advised to take some blood tests. These tests are used to determine the antibodies in the blood specific to the APS. These antibodies include lupus anticoagulant and anti-cardiolipin antibodies or anti-apolipoprotein antibodies. The test is performed twice 12 weeks apart, and the antibodies must be present both times along with the presence of the symptoms. Some people may have antibodies but no symptoms. They are not said to have APS. 

Differential Diagnosis

Some disorders that may also cause symptoms like APS are;

·         Malignancy

·         Use of oral contraceptive pills as it causes hypercoagulability

·         Cholesterol emboli causing atherosclerosis

·         Infective Endocarditis

·         Thrombotic Thrombocytopenic Purpura (TTP)

·         Disseminated Intravascular Coagulation (DIC)


Treatment involves preventing future episodes of thrombosis and thus improvement of the symptoms. This is done by taking blood-thinning medicines, which include heparin and warfarin. Aspirin can be used too, as it also functions as a blood-thinner.

Heparin: This is a fast-acting medicine. It is given by injections. During pregnancy, low molecular weight heparins called enoxaparin and aspirin are used.

Warfarin: This medicine is available in the form of pills. It starts its action after a few days to weeks. It is not given in pregnancy as it harms the developing baby.

Aspirin: Aspirin is also a blood-thinning medicine. It can be given in combination with other medicines.

The side effects of using these medicines include bleeding episodes. So their levels in the blood need to be closely monitored via repeated blood tests to prevent hemorrhages. The parameter used to monitor them is called INR. Its value should remain between 2-3. 


With treatment, the outcome is favorable. Many women are able to give normal healthy babies after the treatment. Without treatment, they may continue to have pregnancy complications. If not treated, APS can be fatal and can result in death due to pulmonary embolism, heart attack, or stroke

Lifestyle Changes

To cope with the disorder, you need to adopt some lifestyle changes to reduce the risk factors associated with thrombosis;

·         Thrombosis is more likely to occur if you smoke, so you better quit smoking.

·         Exercise and maintain a healthy weight. Obesity raises the risk of thrombosis. Exercise reduces the risk of thrombosis, which is especially significant for individuals who sit for hours or travel long distances on flights.

·         If you're flying, get up and move about every now and then. If you're unable to do so, work on your calf muscles. Raise your heels while keeping your toes on the ground, then raise your toes while keeping your heels on the floor.

·         Control your diabetes, high cholesterol levels, and hypertension with proper medicines as they may increase the risk of thrombosis.

·         If you have APS secondary to other autoimmune disorders, you must take proper care of yourself to prevent complications.

·         Taking estrogen in the form of OCPS (Oral contraceptive pills) can increase your risk of thrombosis. Let the doctor know if you have APS. 

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 06, 2023.