Lupus is an autoimmune disease that can affect various parts of the body, including the skin, joints, heart, lungs, blood, kidneys and brain. Normally the body's immune system makes proteins called antibodies, to protect the body against viruses, bacteria, and other foreign materials. These foreign materials are called antigens.

In an autoimmune disorder like lupus, the immune system cannot tell the difference between foreign substances and its own cells and tissues. The immune system then makes antibodies directed against itself. These antibodies -- called "auto-antibodies" (auto means 'self') -- cause inflammation, pain and damage in various parts of the body.

Inflammation is considered the primary feature of lupus. Inflammation, which in Latin means "set on fire," is characterized by pain, heat, redness, swelling and loss of function, either on the inside or on the outside of the body (or both).

For most people, lupus is a mild disease affecting only a few organs. For others, it may cause serious and even life-threatening problems. Although epidemiological data on lupus is limited, studies suggest that more than 16,000 Americans develop lupus each year.

The Lupus Foundation of America (LFA) estimates between 1.5 - 2 million Americans have a form of lupus, but the actual number may be higher. More than 90 percent of people with lupus are women. Symptoms and diagnosis occur most often when women are in their child-bearing years, between the ages of 15 and 45.

In the United States, lupus is more common in African Americans, Latinos, Asians, and Native Americans than in Caucasians.