FGF23 and X-linked dominant hypophosphatemic rickets: FGF23 dependent HR includes X-linked dominant HR (XLHR) caused by loss-of-function mutations in the phosphate regulating endopeptidase homolog, X-linked (PHEX) gene (5), autosomal dominant HR caused by gain of function mutations in the FGF23 gene (6), and three types of autosomal recessive HR.