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What Are the Signs and Symptoms of Antiphospholipid Antibody Syndrome?

The signs and symptoms of antiphospholipid antibody syndrome (APS) are related to abnormal blood clotting. The outcome of a blood clot depends on its size and location.

Blood clots can form in, or travel to, the arteries or veins in the brain, heart, kidneys, lungs, and limbs. Clots can reduce or block blood flow, damaging the body's organs and possibly causing death.

Major Signs and Symptoms

Major signs and symptoms of blood clots include:

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

Blood clots can lead to stroke, heart attack, kidney damage, deep vein thrombosis, and pulmonary embolism.

Pregnant women who have APS are at higher risk for miscarriages, stillbirths, and other pregnancy-related problems, such as preeclampsia.

Preeclampsia is high blood pressure that occurs during pregnancy. This condition may progress to eclampsia. Eclampsia is a serious condition that causes seizures in pregnant women.

Some people who have APS may develop thrombocytopenia. This is a condition in which your blood has a lower than normal number of blood cell fragments called platelets.

Mild to serious bleeding causes the major signs and symptoms of thrombocytopenia. Bleeding can occur inside the body (internal bleeding) or underneath the skin or from the surface of the skin (external bleeding).

Other Signs and Symptoms

Other signs and symptoms of APS include chronic (ongoing) headaches, memory loss, and heart valve problems. Some people who have APS also get a lacy-looking red rash on their wrists and knees.

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Antiphospholipid Antibody Syndrome Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Antiphospholipid Antibody Syndrome, visit

May 17, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.