OI is usually caused by autosomal dominant mutations in the genes encoding procollagen alpha chains (COL1A1/COL1A2), which may cause defects in collagen quantity (a milder form of OI) or in collagen quality due to the abnormal assembly of the protein (moderate-to-severe-to-lethal forms of OI) [100]. This evidence concerns the gene COL1A1 and osteogenesis imperfecta.