Familial hypomagnesemia with hypercalciuria and nephrocalcinosis associated with CLDN16 mutations.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), an autosomal recessive renal tubular disorder, is characterized by the impaired tubular reabsorption of magnesium and calcium in the thick ascending limb of the loop of Henle and an eventual progression to end-stage renal disease. Recent studies have reported that this disease is caused by mutations in the CLDN16 gene, which encodes the tight junction protein, paracellin-1. Paracellin-1 belongs to the claudin family and regulates the paracellular transport of magnesium and calcium. Here, we report on two Korean siblings with typical clinical features of FHHNC in association with compound heterozygous mutations, G233C and 800delG, in CLDN16. Their parents were asymptomatic heterozygous carriers of the single mutations. This is the first report of FHHNC in Korea, and the mutations reported are novel.