Definition of Systemic lupus erythematosus:

Systemic lupus erythematosus (SLE) is a chronic, inflammatory autoimmune disorder. It may affect the skin, joints, kidneys, and other organs.

Causes, incidence, and risk factors:

SLE (lupus) is an autoimmune disease. This means there is a problem with the body's normal immune system response. Normally, the immune system helps protect the body from harmful substances. But in patients with an autoimmune disease, the immune system can't tell the difference between harmful substances and healthy ones. The result is an overactive immune response that attacks otherwise healthy cells and tissue. This leads to chronic (long-term) inflammation.

The underlying cause of autoimmune diseases is not fully known. Some researchers think autoimmune diseases occur after infection with an organism that looks like certain proteins in the body. The proteins are later mistaken for the organism and wrongly targeted for attack by the body's immune system.

SLE may be mild or severe enough to cause death.

SLE affects nine times as many women as men. It may occur at any age, but appears most often in people between the ages of 10 and 50 years. African Americans and Asians are affected more often than people from other races.

SLE may also be caused by certain drugs. For information on this cause of SLE, see drug-induced lupus erythematosus.