FGF23 and ossification of the posterior longitudinal ligament of the spine: To investigate the possibility that ENPP1 deficiency may be an unrecognized contributing factor to spinal enthesopathies in DISH and OPLL, a clinical study examining the skeletal, biochemical, and genetic findings in patients with DISH was performed to investigate the relationship between FGF23, plasma PPi, spinal disease, and genetic background (89).