CRTAP and osteogenesis imperfecta: More than 95% of OI have dominant mutations in COL1A1 or COL1A2, resulting in primary structural or quantitative defects of collagen type I. The recessive forms of OI are caused by mutations in CRTAP, BMP1, CREB3L1, IFITM5, FKBP10, LEPRE1, PPIB, SP7, PLOD2, TMEM38B, SERPINF, SERPINH1, SEC24D, SPARC, WNT1 [1], which lead to defects of proteins interacting with collagen post-translationally.