MON-255 A Novel Variant of SLC34A1 Gene in an Infant with Idiopathic Infantile Hypercalcemia

Bacground & objective: Idiopathic infantile hypercalcemia is one of rare diseases characterizing hypercalcemia in infancy. Renal phosphate absorption in proximal tubules plays a very important role in the phosphate and calcium homeostasis. SLC34A1 is known a key regulator of renal phosphate reabsorption. SLC34A1 gene mutation is one of very uncommon causes of idiopathic infantile hypercalcemia. We have experienced a case of idiopathic infantile hypercalcemia caused by a homozygous novel variant c.1483C>T(p.Arg495Cys) of SLC34A1 gene. Materials & Methods: A study patient was 5 months-old boy. His medical records are reviewed retrospectively. Results: A 5-month-old boy was transferred to Kyungpook National University Children's Hospital because of sustained hypercalcemia with hypercalciuria. Laboratory investigations revealed a serum calcium level of 12.6 mg/dL (normal range: 9.0-10.6 ), phosphate level of 3.7 mg/dL (normal range: 4.8-8.2), serum magnesium level of 2.0 mEq/L (normal range: 1.44-3.12), intact PTH level of 0.6 pg/mL (normal range: 10-65), PTHrP <1.1pmol/L (normal range: <2.0), 25(OH)vitamin D3 level of 65 ng/mL (normal range: 8.0-51.9) and 1,25(OH) vitamin D3 level of 79 pg/mL (normal range: 25-65). Spot urine calcium/urinary creatinine ratio (mg%: mg%) was elevated 1.4 (normal level: <0.8 for infant). Targeted exome sequencing in the patient was performed, resulting in a homozygous novel variant c.1483C>T(p.Arg495Cys) of SLC34A1 gene confirmed by Sanger sequencing. Consulsions: We report a case with idiopathic infantile hypercalcemia caused by a novel variant of SLC34A1 gene mutation