COL1A1 and osteogenesis imperfecta: In 85% of cases, OI is attributed to numerous monogenic variants in the COL1A1(OMIM #120150) or COL1A2(OMIM #120160) genes, which encode collagen type I, while about 15% of cases involve pathogenic variants in genes that commonly affect the biosynthesis pathways of collagen type I [2].