Most commonly, recessive OI involves the collagen prolyl 3-hydroxylation complex, consisting of prolyl 3-hydroxylase 1 (P3H1, encoded by LEPRE1, leucine- and proline-enriched proteoglycan 1), cartilage-associated protein (CRTAP) and cyclophilin B (CyPB, encoded by PPIB, peptidyl-prolyl cis-trans isomerase B). The gene discussed is CRTAP; the disease is osteogenesis imperfecta.