Late presenting, prolonged hypocalcemia in an infant of a woman with hypocalciuric hypercalcemia.

Familial hypocalciuric hypercalcemia (FHH) is a benign autosomal dominant disorder. Infants affected with FHH however, born to unaffected mothers may develop life-threatening autonomous hyperparathyroidism, the mechanism of which is not clearly understood. There is little information recorded in the literature regarding the opposite scenario, i.e., unaffected infants born to affected mothers. Because fetal parathyroid suppression presumably occurs secondary to high maternal calciums, neonatal hypocalcemia would be expected. The authors present a case of an infant with the latter circumstances who presents with late onset, life-threatening hypocalcemia secondary to relative hypoparathyroidism. The authors explored the possibility that vitamin D deficiency and/or acute environmental stress facilitated the decompensation. The patient required therapy for 2 months.