Familial hypocalciuric hypercalcemia in a patient with calcium-sensing receptor mutation: atypical clinical presentation and treatment with cinacalcet

Abstract

Familial hyperparathyroidism including familial hypocalciuric hypercalcemia (FHH) is an heterogeneous subgroup of disorders with Mendelian inheritance, that account for 5% of PTH dependent hypercalcemia. FHH is associated with mutations of the calcium receptor (CaSR) gene. This entity is manifested by hypercalcemia with hypocalciuria and high or normal levels of parathyroid hormone (PTH) generally asymptomatic and with familial presentation. Advances in molecular biology have contributed to the diagnosis, evaluation of the phenotype of each entity and the choice of treatment.
We describe a patient with hypercalcemia diagnosed following the finding of a neck tumor associated with cystic parathyroids. After an exhaustive diagnostic process, an inactivating mutation in the CaSR gene was
found. Considering the presence of a ratio clearance calcium / clearance creatinine <0.01 and the lack of response to surgical treatment, HHF entity with atypical presentation was considered.
The patient exhibited progressive increase in serum calcium following parathyroid surgery, which was not controlled with the use of bisphosphonates and evolved into episodes of frequent dizziness and fainting, without neurological or cardiovascular causes. Treatment with cinacalcet was initiated, with a good
therapeutic response. The use of cinacalcet is a useful therapeutic tool in these rare cases of FHH.