Given its elevated levels in osteogenesis imperfecta (OI), (which exhibits the highest reported concentrations of sclerostin), X-linked hypophosphatemia (XLH), and Paget’s disease of bone (PDB), the assessment of circulating sclerostin may represent a useful adjunct in the diagnostic evaluation of these conditions (33). This evidence concerns the gene SOST and X-linked hypophosphatemia.