X-linked hypophosphatemia (also known as X-linked hypophosphatemic rickets, XLH; OMIM: #307800) is an inherited disease of phosphate metabolism, where inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX, OMIM: #300550) gene lead to local and systemic effects. This evidence concerns the gene PHEX and X-linked hypophosphatemia.