Blood Clotting Disorders
Blood Clotting Disorders

Blood Clotting Disorders Antiphospholipid Syndrome (APS)

What is APS?

What it is

Antiphospholipid syndrome (APS) is an autoimmune disorder that causes abnormal blood clots to form. Autoimmune disorders occur when your body’s immune system  makes antibodies that attack and damage your own tissues or cells.

Normally, antibodies protect your body from viruses or bacteria, but in APS, antibodies attack the body’s healthy cells. High levels of APS antibodies raise the risk of blood clots. The specific antibodies in APS are called “antiphospholipids” because they attack and damage parts of cells called phospholipids. The damage increases the chance that blood clots will form in both veins and arteries.

What are the symptoms?


High levels of APS antibodies in the blood raise the risk of health problems, but some people will never develop blood clots.

Symptoms of abnormal blood clotting include:

  • Chest pain and shortness of breath
  • Nausea (feeling sick to your stomach)
  • Pain, redness, warmth, and swelling in the arms or legs
  • Speech changes
  • Upper body discomfort in the arms, back, neck, and jaw

Less common symptoms of APS include:

  • A lacy-looking red rash on wrists and knees
  • Chronic (ongoing) headaches
  • Heart valve problems
  • Memory loss

What are the risk factors of APS?

Risk factors

Your family history and genes , other medical conditions, medicines and procedures, or lifestyle factors may raise your risk of APS. These factors may raise your risk of APS antibodies, trigger blood clotting in APS, or both. APS can also affect people of any age.

Other common risk factors include:

  • Sex: APS is more common in women than men.
  • Family history: APS may sometimes run in families.
  • Diagnosis of another autoimmune disorder: APS is most common in people who have lupus. In fact, 20% to 30% of people with lupus have antiphospholipid antibodies. Of those, about 1 in 3 develop blood clots in their arteries or veins.
  • Bacterial or viral infections: HIV, hepatitis C, and the bacteria that causes Lyme disease can increase your risk of making APS antibodies or trigger APS.

How will my doctor find out if I have APS?


Your doctor will talk to you about your medical history and may do blood tests. The blood tests look for the three APS antibodies in your blood: anticardiolipin, beta-2 glycoprotein I (β2GPI), and lupus anticoagulant.

To be diagnosed with APS, you must have APS antibodies and a history of health problems related to the disorder. You will likely see a hematologist, which is a doctor who specializes in blood disorders.

How is APS treated?


Currently, APS has no cure. However, medicines can help prevent health problems caused by the condition. The goals of treatment are to prevent blood clots from forming and keep existing clots from getting larger.

Your doctor may prescribe blood thinner medicine such as warfarin, heparin, or aspirin. Your doctor will know which medicine is best for you.

Going to the doctor and getting treatment is important for people with APS. If left untreated, APS can cause life-threatening blood clots that can lead to a heart attack or stroke.

Learn more about how blood clotting disorders such as APS can affect your health.

Untreated APS in pregnancy can result in a higher risk of miscarriages and preeclampsia (high blood pressure during pregnancy).

Research for your health

People with APS are sometimes prescribed blood thinner medicine that they must take for the rest of their lives. Research funded by the NHLBI is investigating alternative treatment options that may help improve the quality of life for people with APS.

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