COL1A1 and osteogenesis imperfecta: The majority of individuals with OI have a disease‐causing mutation in one of the two genes that code for collagen type I alpha chains, COL1A1 and COL1A2. Collagen type I is the main component of the organic bone matrix and therefore plays a key role in the integrity of bone tissue.1, 2, 6 Mutations in 18 genes other than COL1A1 and COL1A2 have been associated with OI phenotypes and are listed in the OI mutation database (https://oi.gene.le.ac.uk).