Guarnieri et al (18) reported a family with FIHP caused by a CDC73 frameshift mutation, where three of 10 mutation carriers had either an atypical parathyroid adenoma (n = 2) or parathyroid carcinoma (n = 1), but only one of the mutation carriers was hypercalcemic. This evidence concerns the gene CDC73 and familial isolated hyperparathyroidism.