Novel homozygous inactivating mutation of the calcium-sensing receptor gene (CASR) in neonatal severe hyperparathyroidism-lack of effect of cinacalcet

The predicted nonfunctional CaSR is consistent with lack of response to cinacalcet, but total parathyroidectomy was successful. An empiric trial of the drug and/or prompt mutation testing should help minimize the period of unnecessary pharmacotherapy.