Lupus anticoagulants are antibodies against substances in the lining of cells that prevent blood clotting in a test tube. These substances are called phospholipids.

Persons with these antibodies may have an abnormally high risk of blood clotting.

See also: Antibody

Lupus anticoagulants are usually found in persons with autoimmune diseases, such as systemic lupus erythematosus (SLE).

They may also be found in persons who take certain medications, including phenothiazines, phenytoin, hydralazine, quinine, and the antibiotic amoxicillin.

Persons with inflammatory bowel disease (Crohn's disease and ulcerative colitis), infections, and certain tumors may have lupus anticoagulants.

Some people have no risk factors for this condition. In some cases, SLE is linked to an increased risk of blood clots and may be the cause of recurrent miscarriages.

You may not have any symptoms. Symptoms that may occur include:

• Blood clots
• Recurrent miscarriages

The following tests may be done:

• Partial thromboplastin time (PTT)
• Russell viper venom time
• Thromboplastin inhibition test

No treatment is required if you do not have symptoms.

If you develop blood clots, your doctor may prescribe blood thinners (heparin followed by warfarin). Higher-than-usual doses of warfarin may be needed.

The outcome is usually good with appropriate therapy. Some patients have difficult-to-control clots with recurrent symptoms.

• Blood clot in lungs (pulmonary embolism)
• Heart attack
• Stroke

Call your health care provider if you notice symptoms of a blood clot, which include swelling or redness in the leg, shortness of breath, or pain, numbness and pallor in an arm or leg.

Awareness of risk factors may allow early diagnosis. Prevention may not be possible.

Harris ED, Budd RC, Genovese MC, Firestein GS, Sargent JS, Sledge CB. Kelley's Textbook of Rheumatology. 7th ed. St. Louis, Mo: WB Saunders; 2005.