Mamedova E, et al. - This report focused on the hereditary forms of primary hyperparathyroidism (PHPT) in patients with the manifestation of the disease under 40 years of age. Accumulated data revealed that hereditary forms of PHPT could be identified in up to 30% of young patients with the manifestation of the disease at <40 years of age. In young patients, parathyroid carcinomas or atypical parathyroid adenomas were frequently associated with CDC73 mutations.