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Who Is at Risk for Antiphospholipid Antibody Syndrome?

Antiphospholipid antibody syndrome (APS) can affect people of any age. The disorder is more common in women than men, but it affects both sexes.

APS also is more common in people who have other autoimmune or rheumatic disorders, such as lupus. ("Rheumatic" refers to disorders that affect the joints, bones, or muscles.)

About 10 percent of all people who have lupus also have APS. About half of all people who have APS also have another autoimmune or rheumatic disorder.

Some people have APS antibodies, but don't ever have signs or symptoms of the disorder. Having APS antibodies doesn't mean that you have APS. To be diagnosed with APS, you must have APS antibodies and a history of health problems related to the disorder.

However, people who have APS antibodies without signs or symptoms are at risk of developing APS. Health problems, other than autoimmune disorders, that can trigger blood clots include:

  • Smoking
  • Prolonged bed rest
  • Pregnancy and the postpartum period
  • Birth control pills and hormone therapy
  • Cancer and kidney disease
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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.