CLDN16 and Hypercalciuria: The defects in the CLDN16 gene are a cause of primary hypomagnesemia (FHHNC) (OMIM # 248250; HOMG3), which is characterized by massive renal magnesium wasting with hypomagnesemia and hypercalciuria resulting in nephrocalcinosis and renal failure (Entrez gene summary: https://www.ncbi.nlm.nih.gov/gene/10686).