Genetically confirming a clinical diagnosis of MEN1 in the proband is mandatory to assess other family members for the presence of the mutation so that they can be followed for potential endocrine problems and for avoiding unnecessary work-up due to “phenocopy.” In the present case, the 14-year-old brother of the proband had asymptomatic hyperparathyroidism. This evidence concerns the gene MEN1 and hyperparathyroidism.