WireImage Lupus is unpredictable, triggering different symptoms in different patients. A chronic illness, it can even attack many different parts of the body. The condition is an autoimmune disease, which means that a person’s immune system—the body system that usually fights infections—attacks healthy tissue instead. It can cause inflammation and pain anywhere in a patient’s body. Because the illness can look different in every patient, it can go undetected and undiagnosed for years. The Lupus Foundation of America estimates that 1.5 million Americans and at least 5 million people worldwide have some form of lupus. There are four forms in all: systemic lupus erythematosus (SLE), lupus confined to the skin, lupus caused by some prescription drugs and a rare lupus that affects infants of women with the disease.