COL1A1 and osteogenesis imperfecta: Mutations in COL1A1 and COL1A2 have also been linked to cases of osteogenesis imperfecta/Ehlers–Danlos overlap syndrome, an allelic disorder which is characterised by patients displaying mixed phenotype of both conditions, which can include joint laxity, atrophic scars, easy bruising, bone abnormality, blue sclerae and vascular fragility [7, 8].