Introduction: Mutations in the SLC34A1 gene (called infantile hypercalcemia 2) cause hypophosphatemia by preventing NaPi-IIa channels from transporting phosphate. Too much active vitamin D into the bloodstream increases the absorption of both phosphate and calcium from the intestines, causing hypercalcemia in affected patients. Hypercalcemia causes high levels of calcium in the urine, causing calcium to accumulate in the kidney tissue and the formation of kidney stones.

Case: A 9-month-old boy was admitted to the hospital with suspicion of urinary tract infection after complaining of vomiting attacks lasting several weeks when he was 1.5 months old. The patient, who was diagnosed with hypercalcemia and nephrocalcinosis during his hospitalization. Renal ultrasound revealed medullary nephrocalcinosis in bilateral kidneys. İn the SLC34A1 gene in genetic analysis homozygous mutation was detected. Although our patient did not have phosphaturia or hypophosphatemia, a known homozygous mutation was found in the NaPi2a protein. In our patient, the phosphate level was found to be normal in the presence of low PTH level and inappropriately normal (141pg/ml) 1,25-dihydroxyvitamin D.

Conclusion: Deletions of the NaPi2a gene and mutations in the SLC34A gene should be considered in patients with atypical presentation, no phosphaturia, normal serum phosphate level, and medullary nephrocalcinosis.