PHEX and hypophosphatemic rickets: X-linked dominant hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets (ADHR), and autosomal recessive hypophosphatemic rickets (ARHR) are the three main types of hypophosphatemic rickets and are associated with mutations in the phosphate-regulating endopeptidase gene (PHEX), the fibroblast growth factor 23 gene (FGF23), and the dentin matrix acidic phosphoprotein1 gene (DMP1), respectively.