Mutations in COL1A1 and COL1A2 of collagen-related OI can be divided into two groups: quantitative defect (haploinsufficiency) with synthesizing about half the amount of structurally normal type I collagen, primarily resulting from nonsense, frameshift, and some splice-site variants; another is the structural defect, in which over 80% mutations are the results of glycine substitutions in the helical domain (4). Here, COL1A2 is linked to osteogenesis imperfecta.