Research advances have shown that different genetic mutations acting through shared molecular pathways can cause similar skeletal phenotypes [e.g., osteogenesis imperfecta (OI) results from disruptions in genes encoding type I collagen (COL1A1 and COL1A2) and genes encoding molecular chaperones (e.g., SERPINH1 and FKBP10)], as well as that different skeletal dysplasias can result from mutations in the same gene (e.g., mutations in the FGFR3 cause achondroplasia, hypochondroplasia, and thanatophoric dysplasia) (6, 7). The gene discussed is COL1A2; the disease is osteogenesis imperfecta.