Approximately 90% of the 3,000 individuals whose mutations have been included in the OI variant database1 have alterations in either COL1A1 or COL1A2. In view of the above situation, we defined the OI patients with COL1A1 and COL1A2 gene mutations as common mutations, and the patients with OI with other gene mutations as rare mutations. The gene discussed is COL1A2; the disease is osteogenesis imperfecta.