Cole-Carpenter syndrome (CCS) is a severe bone fragility disorder that is characterized by frequent fractures, craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features. CCS was first described in 1987 as a newly recognized type of osteogenesis imperfecta (OI). Despite its apparent extreme rarity, CCS is commonly classified as a separate OI-like disorder. CCS is caused by a specific de novo mutation in P4HB, the gene that encodes protein disulfide isomerase (PDI), that impairs the disulfide isomerase activity. Mutations in SEC24D, a gene encoding a component of the COPII complex machinery, have been reported to cause CCS as well.
