Antiphospholipid Syndrome

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What is antiphospholipid syndrome?

Antiphospholipid syndrome (APS) is a rare autoimmune disorder caused when antibodies—immune system cells that fight off bacteria and viruses—mistakenly attack normal proteins in the blood. Specific antibodies activate the inner lining of blood vessels, which leads to the formation of blood clots in arteries or veins in the brain, legs, kidneys, and lungs.

APS is sometimes called “sticky blood syndrome”  because of the increased tendency for blood clots to form. A clot that forms in the brain can interrupt the flow of blood and cause a stroke. Other neurological symptoms may include:

  • chronic headaches
  • dementia (similar to the dementia of Alzheimer's disease)
  •  seizures
  • chorea (a movement disorder in which the body and limbs writhe uncontrollably)
  • cognitive dysfunction, such as poor memory
  • transverse myelitis, an inflammation of the spinal cord
  • depression or psychosis
  • damage to the optic nerve
  • sudden hearing loss

    APS affects fewer than 200,000 people. Treatment is aimed at thinning the blood to prevent clots from forming and to keep existing clots from getting larger. Treatment should be lifelong. Doctors often recommend that individuals stop smoking, exercise regularly, and eat a healthy diet to prevent high blood pressure and diabetes, which are diseases that increase the risk for stroke. 

    Learn About Clinical Trials
    Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

    How can I or my loved one help improve care for people with antiphospholipid syndrome?

    Consider participating in a clinical trial so clinicians and scientists can learn more about antiphospholipid syndrome and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

    All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

    For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with antiphospholipid syndrome at

    Where can I find more information about antiphospholipid syndrome?

    Information is available through the following resources:

    Genetic and Rare Diseases (GARD) Information Center


    Order publications from the NINDS Catalog
    The NINDS Publication Catalog offers printed materials on neurological disorders for patients, health professionals, and the general public. All materials are free of charge, and a downloadable PDF version is also available for most publications.