COL1A2 and osteogenesis imperfecta: Despite exhibiting a similar osteopenia phenotype, osteogenesis imperfecta (OI) is distinguished from osteoporosis by its impaired bone mineralization rather than abnormal bone remodeling.419 Most OI cases are characterized by mutations in genes encoding type I collagen, such as COL1A1 or COL1A2, with other gene mutations observed in 15–25% of cases.420 Five primary clinical forms of OI have been identified by nosology and classification of genetic skeletal disorders.421 Unfortunately, gene-specific therapies have yet to be feasible for OI.