Background: X-linked hypophosphatemic rickets (XLH) is an X-linked dominant disease characterized by renal phosphate wasting, hypophosphatemia, aberrant vitamin D metabolism, and defective bone mineralization. The disease is caused by mutations in the PHEX gene (phosphate-regulating gene with homologies to endopeptidases on the X-chromosome) located at Xp22.1. To date, a variety of PHEX mutations have been identified in these patients.

Methods: PCR and direct sequencing was performed for all exons and intron-exon boundaries of the PHEX gene in two XLH families.

Results: Two novel mutations, including a missense mutation (L206W) in exon 5 and a frameshift mutation (nucleotide 1826_1830delAAAAG, stop after codon 610) in exon 18 were discovered and the laboratory and radiographic findings for these patients analyzed.

Conclusions: We found that PHEX gene mutations were responsible for XLH in these Taiwanese patients. Additional studies are needed to enhance understanding of the role of PHEX in XLH pathogenesis.