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). Here, ENPP1 is linked to ossification of the posterior longitudinal ligament of the spine.