It is caused by pathogenic variants in the PHEX (phosphate-regulating neutral endopeptidase homolog X-linked) gene which is mainly expressed in the bone and teeth, resulting in elevated circulating levels of the phosphaturic hormone fibroblast growth factor 23 (FGF23) causing renal phosphate wasting and impaired synthesis of 1,25-dihydroxyvitamin D (1,25(OH)2D) and consecutive hypophosphatemia. Here, FGF23 is linked to hypophosphatemia.