Primary hyperparathyroidism is a constitutive excess of parathyroid hormone (PTH) in the blood, caused by an idiopathic defect of growth and/or function of the parathyroid glands. PHPT is usually an acquired disease, due to the sporadic development of parathyroid hyperplasia, adenoma, and, in extremely rare cases, malignant carcinoma, mainly occurring by the sixth decade of life. In about 5-10 % of cases PHPT manifests in the context of congenital disorders, having a genetic base and occurring much earlier in life, compared to the sporadic counterpart. Congenital PHPT can manifest as isolated PHPT or as syndromic PHPT in the context of complex multiorgan disorders. Non-syndromic inherited PHPT includes Familial Hypocalciuric Hypercalcemia types 1, 2 and 3, Neonatal Severe Primary Hyperparathyroidism, and three different genetic forms of Familial Isolated Hyperparathyroidism, while syndromic inherited PHPT includes Hyperparathyroidism-Jaw Tumor Syndrome and Multiple Endocrine Neoplasias types 1, 2 A and 4.