Novel Mutation in the Calcium-Sensing Receptor Gene Associated With Familial Hypocalciuric Hypercalcemia

We present a case of a 75-year-old woman with persistent hypercalcemia (serum calcium 10.7 mg/dL, ionized calcium 1.37 mmol/L), elevated parathyroid hormone levels (86.6 pg/mL), and significantly low 24-hour urinary calcium excretion (<11 mg/24 hours). Genetic testing identified a novel heterozygous variant in the calcium-sensing receptor (CaSR) gene, c.3166G>C (p. Val1056Leu). The patient's biochemical profile and the identification of the CaSR variant support the diagnosis of familial hypocalciuric hypercalcemia (FHH). The novel c.3166G>C (p.Val1056Leu) variant has not been previously reported in FHH or other CaSR-associated conditions. Its presence in this patient suggests a potential role in the clinical manifestation of FHH. However, it is currently classified as a variant of undetermined significance (VUD) in the ClinVar database, necessitating further research on the clinical relevance of this variant in FHH. This case highlights the significance of genetic testing in diagnosing FHH and the potential clinical impact of discovering novel CaSR gene mutations. Further research on the genetics associated with FHH is necessary to better understand the condition, detect it early, and manage it effectively, thereby improving patient care and outcomes.