FGF23 and craniosynostosis: Finally, FGF23-mediated hypophosphatemia has been reported in two ultrarare skeletal dysplasias: osteoglophonic dysplasia (characterized by rhizomelic dwarfism, craniosynostosis, impacted teeth, hypodontia or anodontia, and multiple non-ossifying bone lesions) (75) and opsismodysplasia (a rare spondylo(epi)chondrodysplasia characterized by delayed skeletal maturation) (76).