A girl diagnosed with familial hypocalciuric hypercalcemia with heterozygous p.Cys575Tyr variation in the CaSR gene

Familial hypocalciuric hypercalcemia (FHH) is a benign disease associated with heterozygous inactivating mutations in the calcium-sensing receptor (CaSR) gene. This article presents a girl with heterozygous p.Cys575Tyr variation in the CaSR gene. The serum calcium level of a 9.2-year-old girl was 12.4mg/dl in incidental laboratory analysis. On the same occasion, the serum parathyroid hormone (PTH) level was 45 pg/ml, 25(OH) vitamin D level 24.2ng/ml, 1.25 dihydroxy vitamin D level 22pg/ml, and urinary Ca/creatinine ratio <0.01. The ultrasonographic evaluation of the urinary system was unremarkable. The clinical and laboratory findings pointed towards FHD. A heterozygous p.Cys575Tyr (c.1724G>A) variation was detected in the patient’s CaSR gene, which was reported before, but no clinical manifestations were specified. In children with asymptomatic hypercalcemia, the diagnosis of FHH should be considered if the PTH level is normal or high and the urinary calcium is low.

Keywords: Hypercalcemia, familial hypocalciuric hypercalcemia, calcium-sensing receptor (CaSR)