Lupus is an autoimmune disease where the immune system attacks its own tissues. There are two main types: discoid lupus which only affects the skin, and systemic lupus erythematosus (SLE) which can impact internal organs like the heart, lungs and kidneys. SLE is more common in women and typically develops between ages 20-45. Symptoms can include rashes, arthritis, organ inflammation and damage. The cause is unknown but genetics and environmental factors may play a role. Diagnosis involves looking for at least 4 of 11 specific clinical criteria.