LCT and nephrocalcinosis: Concurrent CSID and nephrolithiasis was first described in 1970, though the pathogenesis was not clarified.21 Belmont et al22 claimed that sucrase–isomaltase and lactase play a role in intestinal calcium homeostasis and that in the event of deficiency, nephrocalcinosis secondary to hypercalcemia may occur with the upregulation of the 1,25-OH-VitD3 receptor.