SAT-351 A Novel Mutation in the Calcium-Sensing Receptor Gene Presenting in a Kindred as Autosomal Dominant Familial Hypocalciuric Hypercalcemia

Rationale: Familial hypocalciuric hypercalcemia (FHH) is a benign cause of hypercalcemia. The majority of cases result from an inactivating mutation in the calcium-sensing receptor (CaSR). While affected patients are usually asymptomatic and require no treatment, this condition may go unrecognized and inappropriate parathyroidectomy for presumed primary hyperparathyroidism could be performed. Over 130 mutations in the CaSR gene have been reported and novel variants continue to emerge. Methods: The initial patient was a 49 year-old female who presented with mild hypercalcemia, elevated PTH and undetectable urine calcium. She reported several of her family members had elevated calcium levels. Given high clinical suspicion for FHH genetic analysis was performed. Results: Sequencing of the CaSR gene revealed a point mutation at c.1744T>A which resulted in p.Cys582Ser in exon 7. This cystine residue is highly conserved and predictive algorithms suggest this variant is likely disruptive leading to heterozygous loss of function in the CaSR. The patient’s 26 year-old daughter was tested and found to have the same mutation. Conclusion: We report the identification of a novel heterozygous mutation in the CaSR gene manifesting as FHH in a family of Iraqi decent. Additional family members are currently undergoing genetic analysis which will be included at the time of presentation.