We were unable to definitively elucidate the mechanism of hypercalcemia in our case due to the unavailability of PTHrP/CYP27B1 (1-alpha-hydroxylase) immunohistochemical staining and serum assays for PTHrP and 1,25-dihydroxyvitamin D at our institution. The gene discussed is CYP27B1; the disease is hypercalcemia disease.