Lupus anticoagulant

Definition:

An immunoglobulin that interferes with blood coagulation (clotting) and has antithromboplastin activity.

Causes, incidence, and risk factors:

Lupus anticoagulant is a specific immunoglobulin that prolongs the time it takes blood to clot but does not produce a bleeding disorder. It occurs in approximately 25% of people who have lupus erythematosus, and is also seen in people who take phenothiazine medication, as well as in otherwise normal people. In some people it is associated with an increased risk of blood clots and may be the cause of recurrent spontaneous abortions. If a secondary disorder such as thrombocytopenia is present, bleeding will probably occur. Risk factors are lupus erythematosus and recent use of phenothiazine medication.