Spectrum and natural history of congenital hyperparathyroidism secondary to maternal hypocalcemia.

Fourteen cases of congenital hyperparathyroidism secondary to maternal hypocalcemia have been reported. We report two additional cases that highlight the wide spectrum of the disease. We extensively studied the parathyroid function of these infants to test the hypothesis that the biochemical hyperparathyroidism found in these infants would be transient in nature, since the presumed etiology (maternal and subsequent fetal hypocalcemia) should disappear soon after birth with establishment of enteral feedings. Infant 1 was born to a mother with idiopathic hypoparathyroidism with poor compliance to therapy and documented hypocalcemia in pregnancy. Severe congenital demineralization and intrauterine fractures with clinical and radiologic bowing of the long bones were obvious. Bone mineral content and bone mineral content/bone width ratio, measured by photon absorptiometry, were both markedly below normal. Infant 2 was born to a mother with postsurgical hypoparathyroidism with excellent compliance. The mother was normocalcemic. The infant was clinically and radiologically asymptomatic. The bone mineral content was just at the lower limit of normal, but bone mineral content/bone width ratio was below the normal limits. Biochemical features include elevation of cord serum parathyroid hormone (1-84, radioimmunoassay) in both cases, coexisting with serum calcium, phosphorus concentrations within normal limits. Serum parathyroid hormone fell to within normal ranges by 9 days of age in both infants. With no treatment, bone mineral content at 1 month of age was normal in both infants.