Association of Mutations in SLC12A1 Encoding the NKCC2 Cotransporter With Neonatal Primary Hyperparathyroidism.

CONTEXT Primary hyperparathyroidism with hypercalciuria has not been described in the newborn period. OBJECTIVE Our objectives are to identify the genetic basis for neonatal primary hyperparathyroidism in a family with 2 affected children. SUBJECTS An African American boy presenting with mild neonatal primary hyperparathyroidism and hypercalciuria was evaluated at The Children's Hospital of Philadelphia. His older brother with neonatal primary hyperparathyroidism had died in infancy of multiple organ failure. METHODS We collected clinical and biochemical data and performed exome sequencing analysis on DNA from the patient and his unaffected mother after negative genetic testing for known causes of primary hyperparathyroidism. RESULTS Exome sequencing followed by Sanger sequencing disclosed 2 heterozygous mutations, c.1883C>A, p.(A628D) and c.2786_2787insC, p.(T931fsX10), in the SLC12A1 gene, which was previously implicated in antenatal type 1 Bartter syndrome. Sanger sequencing confirmed the 2 mutations in the proband and his deceased brother; both parents were heterozygous for different mutations and an unaffected sister was homozygous for wild-type alleles. CONCLUSIONS These results demonstrate a previously unrecognized association between neonatal primary hyperparathyroidism and mutation of SLC12A1, the cause of antenatal Bartter syndrome type 1, and suggest that the loss of sodium-potassium-chloride cotransporter-2 cotransporter activity influences parathyroid gland function.