COL1A1 and osteogenesis imperfecta: Yousuke Higuchi et al., having carried out Sanger sequencing of the COL1A1/2 and IFITM5 genes in 96 Japanese OI probands, 44 of whom had an OI family history, found that 56.3% of patients had a mild form of OI type I, 42.7% had a moderate-to-severe form of OI types II–IV, and 1.0% had OI type V. Thus, 90% of all OI cases are caused by variants in the COL1A1 and COL1A2 genes.