CYP24A1 and Hypercalcemia: Autosomal recessive inheritance of mutations in the sodium-phosphate co-transporter NaPi2a, encoded by SLC34A1, cause idiopathic infantile hypercalcaemia (IIH), classified as hypercalcaemia, infantile 2 (HCINF2), in a subgroup of patients without CYP24A1 mutations [25].