Systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) are long-term
autoimmune diseases in which the immune system attacks parts of the body. The abnormal
immune reaction causes inflammation of and damage to various body parts and can affect
joints, skin, kidneys, heart, lungs, blood vessels, and the brain. SLE and MCTD often affect
young women, especially black and Hispanic women, and there is no known cure. Knowing more
about SLE and MCTD will help in developing new and effective treatments. The purpose of this
study is to characterize immune system abnormalities, genetic components, and disease
progression in people with SLE and MCTD.