COL1A1 and osteogenesis imperfecta: Previous studies have shown that 80%–85% of OI cases are caused by abnormal synthesis and processing of type I collagen due to heterozygous variants in the genes encoding the α1 (COL1A1) or α2 (COL1A2) chains of type I collagen, which are inherited in an autosomal dominant (AD) pattern [5,8].