This study provided the first evidence in humans of the critical role that NaPi2a plays in human renal phosphate handling.173 Subsequently, novel loss-of-function mutations in SLC34A1 were identified in members of families with idiopathic infantile hypercalcemia (IIH) not attributed to abnormalities in inactivation of vitamin D processsing, many with nephrocalcinosis.174,175. Here, SLC34A1 is linked to hypercalcemia, infantile.