Neonatal severe primary hyperparathyroidism (NSPHT) (MIM 239200) is a rare di- sorder that presents at birth or within the first six months of life and is characterized by severe life-threatening hypercalcemia, hypermagnesemia, increased circulating PTH levels, massive hyperplasia of the parathyroid glands and relative hypocalciuria. This evidence concerns the gene PTH and primary hyperparathyroidism.