As a result of the increased FGF23 concentrations patients with XLH, ADHR, ARHR type 1 and 2 present with rickets, hypophosphatemia, phosphaturia and inappropriately normal serum 1,25-dihydroxyvitamin D3 concentrations [9], [30]. The gene discussed is FGF23; the disease is X-linked dominant hypophosphatemic rickets.