X-linked hypophosphatemic rickets/osteomalacia (XLH) is an X-linked dominantly inherited rare disease presenting with persisting hypophosphatemia and impaired bone mineralization due to excessive fibroblast growth factor 23 (FGF23) caused by loss-of-function variants in the phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) gene [1–5]. This evidence concerns the gene FGF23 and hypophosphatemia.