Our institution also had previously reported hypophosphatemic rickets associated with eight types of PHEX gene mutations but found no phenotype-genotype correlation due to the small patient number (12); another Korean study at another institution analyzed several hereditary rickets and revealed that mutations in the C-terminal half of the PHEX gene were associated with a severe bony phenotype; however, this study did not focus on XLH (13). The gene discussed is PHEX; the disease is X-linked hypophosphatemia.