According to the effects of gene mutation on synthesis of type I collagen, OI patients with COL1A1 or COL1A2 mutation were further divided into three subgroups, including haplo-insufficiency of type I collagen (n = 21), triple-helical structure change (n = 15), and others (n = 13). Here, COL1A2 is linked to osteogenesis imperfecta.