Mutations in the SLC34A3 gene, encoding the sodium/phosphate cotransporter 2C (NPTIIc), induce decreased renal phosphate reabsorption, hypophosphatemia, decreased fibroblast growth factor 23 and parathyroid hormone, and increased 1,25-dihydroxyvitamin D (1,25[OH]2D) levels. The complete phenotype is characterized by hypophosphatemia, hypercalciuria, and nephrolithiasis/nephrocalcinosis, leading to chronic kidney disease and osteoporosis in adults. We report a 15-year-old boy referred for nephrocalcinosis.