Pathogenic variants in the prolyl 3-hydroxylase 1 (P3H1, OMIM#: 610339) gene were discovered in 2006 as a cause of severe recessive OI, genetic type VIII (OMIM#: 610915) [3,6]; although the clinical types 2 and 3 OI are commonly reported, milder cases also exist [7]. The gene discussed is P3H1; the disease is osteogenesis imperfecta.