PPIB is identified as a candidate gene for OI-IX.Osteogenesis imperfecta (OI) is an inherited disorder of connective tissue typically caused by defects in either COL1A1 or COL1A2. A number of other genes causative of this disorder have been found, including PPIB, which forms one subunit of the prolyl 3-hydroxylase enzyme complex.Patients with OI caused by PPIB mutation should have appropriate early and regular management of their hearing.