Lupus is an autoimmune (AW-toe-ih-MYOON) disease. Your body's immune system is like an army with hundreds of soldiers. The immune system's job is to fight foreign substances in the body, like germs and viruses. But in autoimmune diseases, the immune system is out of control. It attacks healthy tissues, not germs.

You can't catch lupus from another person. It isn't cancer, and it isn't related to AIDS.

Lupus is a disease that can affect many parts of the body. Everyone reacts differently. One person with lupus may have swollen knees and fever. Another person may be tired all the time or have kidney trouble. Someone else may have rashes. Lupus can involve the joints, the skin, the kidneys, the lungs, the heart and/or the brain. If you have lupus, it may affect two or three parts of your body. Usually, one person doesn't have all the possible symptoms.

There are three main types of lupus:

• Systemic lupus erythematosus (eh-RITH-eh-muh-TOE-sus) is the most common form. It's sometimes called SLE, or just lupus. The word "systemic" means that the disease can involve many parts of the body such as the heart, lungs, kidneys, and brain. SLE symptoms can be mild or serious.

• Discoid lupus erythematosus mainly affects the skin. A red rash may appear, or the skin on the face, scalp, or elsewhere may change color.

• Drug-induced lupus is triggered by a few medicines. It's like SLE, but symptoms are usually milder. Most of the time, the disease goes away when the medicine is stopped. More men develop drug-induced lupus because the drugs that cause it, hydralazine and procainamide, are used to treat heart conditions that are more common in men.