An Association between Neonatal Severe Primary Hyperparathyroidism and Familial Hypocalciuric Hypercalcemia in Three Kindreds

Four cases of neonatal severe primary hyperparathyroidism occurred in three families; familial hypocalciuric hypercalcemia was present in each kindred. The diagnosis of familial hypocalciuric hypercalcemia was based on the following features: hypercalcemia in many relatives (eight to 16 per kindred), without other features of the multiple endocrine neoplasia syndromes; recognition of hypercalcemia before the age of 10 in one to three relatives; hypocalciuric hypercalcemia in all relatives tested (five to 14 per kindred); and abnormal serum calcium levels despite parathyroidectomy in all additional relatives (one to five per kindred) undergoing this operation. The association of two uncommon syndromes (neonatal severe primary hyperparathyroidism and familial hypocalciuric hypercalcemia) in these kindreds suggests that the two syndromes share a common genetic cause within each kindred. (N Engl J Med. 1982; 306:257–64.), NEONATAL severe primary hyperparathyroidism is a syndrome characterized by hypercalcemia, muscular hypotonia, skeletal undermineralization, and a high rate of mortality.^{1 2 3 4 5 6 7 8 9 10 11 12 13} In 1967 Mühlethaler et al. called attention to the fact that in all reported cases, this syndrome had been associated with parathyroid hyperplasia and never with parathyroid adenoma.⁶ Little else is known about its cause, but expression of the disease near the time of birth suggests a disturbance of mineral homeostasis in utero. We recently observed that many of the previously described patients with neonatal severe primary hyperparathyroidism had certain clinical and biochemical features similar to those in adults with.