P3H1 and osteogenesis imperfecta type 8: Among others, OI type VIII is triggered by defects in prolyl 3-hydroxylase 1 (P3H1), a member of the endoplasmic reticulum (ER) resident prolyl 3-hydroxylation complex that is involved in the 3-hydroxylation of the α1(I)-Pro986 and in supporting collagen I triple helix folding and assembly.1