Lupus, or systemic lupus erythematosus (SLE), is an inflammatory disease resulting from an abnormality in the body’s immune system regulation. It is an unpredictable disease, varying a great deal from one case to another. A potentially serious disorder, systemic lupus erythematosus affects women much more often than men. In about eighty percent of SLE cases, joint inflammation occurs. The inflammation may affect connective tissues throughout the body and cause problems in one or more of the body's organs, including the eyes, muscles, heart, lungs, and kidneys. In some people, systemic lupus erythematosus can produce potentially life-threatening complications, including kidney failure.