At a median age of 10.8 (2.0–14.4) years, 18 patients received cinacalcet for primary HPT (N = 13 inactive CASR mutation, N = 1 CDC73 mutation, N = 1 multiple endocrine neoplasia type 1, N=3 unknown etiology). The gene discussed is CDC73; the disease is multiple endocrine neoplasia type 1.