Lupus is a chronic inflammatory disease that occurs when your body's immune system attacks your own tissues and organs. Mayo Clinic rheumatologist Thomas Osborn, M.D., says the inflammation caused by lupus can affect many different body systems — including your joints, skin, kidneys, blood cells, brain, heart and lungs.

Dr. Osborn adds that lupus can be difficult to diagnose because its signs and symptoms often mimic those of other ailments. The most distinctive sign of lupus — a facial rash that resembles the wings of a butterfly unfolding across both cheeks — occurs in many but not all cases of lupus.