COL1A1 and osteogenesis imperfecta: OI types I-IV are mainly associated with autosomal dominant variants in COL1A1 and COL1A2; OI type V is a less frequent dominantly inherited form associated with variants in the novel gene IFTM5. The remaining types of OI, which usually arise at much lower frequency are autosomal recessive diseases while OI type XVIII has an X-linked inheritance pattern [2,4].