Though the majority of OI cases are caused by variants in COL1A1 and COL1A2 genes, a large number of genes, including genes crucial for osteoblast and osteocyte function, have been identified to cause skeletal fragility and a phenotype similar to “classic” (collagen-mutated) OI [124, 125]. The gene discussed is COL1A2; the disease is osteogenesis imperfecta.