CLDN19 and Hypercalciuria: Mutations in Cldn16 or Cldn19 that encode claudin-16 and claudin-19, respectively, cause familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) (OMIM: 248250), which is an autosomal-recessive renal tubular disorder which sees nephrocalcinosis as a main symptom [3,4,5].