COL1A1 and metaphyseal chondrodysplasia: ER stress-induced apoptosis has been demonstrated to be a common mechanism leading to various skeletal disorders, such as metaphyseal chondrodysplasia, Schmid type (OMIM#156500), pseudoachondroplasia (OMIM#177170), and COL1A1-related osteogenesis imperfecta (OMIM#166200)31–33.