A recent sequencing study in close to 600 individuals with a clinical diagnosis of OI found disease‐causing mutation in 97% of patients with OI type I (all of whom had COL1A1 or COL1A2 mutations) and in 99% of individuals with the more severe OI types (77% had COL1A1 or COL1A2 mutations).16 Thus, even though some OI genes remain to be discovered, they can be expected to affect only a small number of individuals with a typical OI phenotype. This evidence concerns the gene COL1A1 and osteogenesis imperfecta.