ESPE Abstracts

The calcium-sensing receptor (CaSR) is a member of the G protein coupled receptor family. It is mostly found in the parathyroid gland and renal tubule. CaSR disorders occur with inherited or acquired mutations. Familial hypocalciuric hypercalcemia syndromes are associated with inactivating mutations in CaSR. The heterozygous form is “benign familial hypercalcemia” and the homozygous form is “neonatal hyperparathyroidism”. In this article, “benign familial hypercalcemia” cases are presented and it is emphasized that asymptomatic cases can be encountered incidentally. A 10 year old male patient was referred to our outpatient clinic due to high calcium levels. In the evaluation; there was no consanguinity between the mother and father of the patient, whose height was 142.3 cm (50-75p), and weight was 41.9 kg (75-90p). His general condition was good, and system examinations were normal. Systolic and diastolic blood pressures were within normal limits for age. In the blood tests of the patient, Ca: 11.31 mg/dl, ALP: 306 U/l, Mg: 2.15 mg/dl, P: 3.65 mg/dl, PTH: 73.6 ng/l, 25(OH) vitamin D: 11.4 ng/ml, fT4: 1.13 pg/ml, TSH: 3.27 mU/l and urinary calcium/creatine: 0.01 mg/dL. After detailed evaluations and DNA sequence analysis, CASR gene c.2532_2539delCAGCTTT (P.Ser845fs*133) mutation was detected as heterozygous. This variant was evaluated as a 'probably pathogenic variant' explaining the patient's clinical findings. After the patient's detailed family history, detailed physical examination and laboratory tests were performed on his sister, who was older than her age. Ca: 11.7 mg/dl, ALP: 325 U/l, Mg: 2.1 mg/dl, P: 5.4 mg/dl, PTH: 12.3 ng/l, 25(OH) vitamin D: 29, urinary calcium/creatine: 0.01 mg/dL. Genetic analysis was performed and the same mutation was found in his sister. Genetic analysis was performed in the mother and grandmother in the family with familial benign hypocalciuric hypercalcemia, and the same CASR mutation was found. After the patients were hydrated, no additional problems were encountered. The follow-up of the patients continues in our outpatient clinic. Considering the diagnosis of familial benign hypocalciuric hypercalcemia in a patient with hypercalcemia after evaluating all the factors that may affect calcium metabolism, the familial history of these cases and similar clinical findings will often distract the physician from misdiagnosis. In the diagnostic approach of hypercalcemia, it will be beneficial to keep the diagnosis of familial benign hypocalciuric hypercalcemia in mind.