COL1A1 and osteogenesis imperfecta: In the TOPaZ study, pathogenic variants in COL1A1 or COL1A2 were found in 85%, but other implicated genes included FKBP10, IFITM5, P3H1, and BMP1. Interestingly, no pathogenic variants could be detected in genes in 31 individuals (8.9%) despite the fact they had been diagnosed clinically with OI.