Moreover, plasma PPi in the Hyp mouse, a murine model of XLH induced by PHEX mutations, is also reported to be decreased, supporting the notion that reduced plasma PPi may induce the enthesopathies in XLH and ARHR2, resulting in spinal ossification and an OPLL phenotypes in these diseases [113]. This evidence concerns the gene ENPP1 and X-linked hypophosphatemia.