This disease is characterized by the progressive calcification of soft tissues leading to symptoms of pressure and hyperphosphatemia but normal concentrations of serum calcium with or without an elevation of 1,25-dihydroxyvitamin D3 levels.HFTC is caused by loss-of-function mutations in the GALNT3, FGF23 or KL genes. The gene discussed is FGF23; the disease is hyperphosphatemia.