Decorin is also known as bone proteoglycan II, PGS2, SLRR1B, DCN, DSPG2 and PG40, is a secreted chondroitin /dermatan sulfate proteoglycan in the family of small leucine-rich proteoglycans (SLRPs). Decorin is a small cellular or pericellular matrix proteoglycan and is closely related in structure to biglycan protein. Decorin and biglycan are thought to be the result of a gene duplication. This protein is a component of connective tissue, binds to type I collagen fibrils, and plays a role in matrix assembly. Decorin appears to influence fibrillogenesis, and also interacts with fibronectin, thrombospondin, the complement component C1q, epidermal growth factor receptor (EGFR) and transforming growth factor-beta (TGF-beta). Defects in DCN are the cause of congenital stromal corneal dystrophy (CSCD).