SLC34A1 and Hypercalciuria: New genetic mutations in vitamin D metabolism and urinary phosphate excretion have also been identified as causes of previously labelled “Idiopathic Infantile Hypercalcaemia.” Loss-of-function mutation in CYP24A1 [encoding vitamin D breakdown enzyme 25(OH) vitamin D3 24-hydroxylase] and in SLC34A1 (encoding renal proximal tubular NaPi co-transporter) and NHERF1 (a modifier of SLC34A1) cause accumulation of calcitriol, hypercalcaemia, hypercalciuria, and nephrocalcinosis (19, 46).