Laboratory evaluation revealed severe hypophosphatemia, inappropriately low normal 1,25-dihydroxy vitamin D despite being on cholecalciferol and calcitriol, normal 25-hydroxy vitamin D, normal calcium level, normal serum albumin, normal serum creatinine, low 24-hour urinary calcium excretion, and normal parathyroid hormone (PTH) (Table 1). The gene discussed is PTH; the disease is hypophosphatemia.