X-linked hypophosphatemic rickets (XLH) is the most common form of hereditary rickets. Here, we present a case of XLH associated with a novel mutation in a phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX). PCR-direct sequencing revealed a novel PHEX mutation in exon 22, NM_000444.6(PHEX):c.2202del [p.Asn736Ilefs*4], near the 3'-UTR region encoding the COOH-terminal extracellular domain. In silico analysis indicated that a single mutation in N736 may have caused a significant change in higher-order protein structure and function.