ESPE Abstracts

Bacground and 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 and methods: A study patient was 5 months-old boy. His medical records were 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 <1.1 pmol/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.