Although the majority of heterozygous mutations in COL1A1 or COL1A2, encoding the pro-α1- and pro-α2-chain of type I collagen, respectively, result in the brittle bone disorder osteogenesis imperfecta (OI), specific type I collagen defects can also give rise to rare EDS subtypes. The gene discussed is COL1A2; the disease is Ehlers-Danlos syndrome.