The protein follistatin-like 1 (FSTL1), also known as transforming growth factor-stimulated clone 36 (TSC-36) or follistatin-related protein (FRP), is a soluble secreted extracellular glycoprotein that plays an important role in many kinds of tissue degeneration and autoimmune diseases [21, 22]. This evidence concerns the gene FSTL1 and autoimmune disease.