Lupus anticoagulants are antibodies against phospholipids (substances in the lining of cells) that prevent blood clotting in a test tube. 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, amoxicillin, and birth control pills. 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, it is linked to an increased risk of blood clots and may be the cause of recurrent miscarriages.

• Blood clots
• Recurrent miscarriages

There may be no symptoms.

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

No treatment is required when there are no symptoms. If clots occur, your health care provider may prescribe blood thinners (heparin followed by warfarin). Higher-than-usual doses of warfarin may be needed. Steroids sometimes help lower antibody levels, but it is not clear whether this decreases clotting risk.

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

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

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.