Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. The reason the term lupus was used to describe this disease comes from the mid-19th century. Many diseases that caused ulceration or necrosis were given the term "lupus" due to the wound being reminiscent of a wolf's bite.