The associated syndromic disorders include multiple endocrine neoplasia types 1–5 (MEN1-5) and hyperparathyroidism with jaw tumor (HPT-JT) syndromes, and the non-syndromic forms include familial hypocalciuric hypercalcemia types 1–3 (FHH1-3), familial isolated hyperparathyroidism (FIHP), and neonatal severe hyperparathyroidism (NS-HPT). Here, MEN1 is linked to neonatal severe primary hyperparathyroidism.