CLDN16 and familial primary hypomagnesemia with hypercalciuria and nephrocalcinosis: This case demonstrates the critical role of whole-exome sequencing (WES) in diagnosing FHHNC, particularly when novel mutations, such as the homozygous CLDN16 variant (c.351G > T, p.W117C) found in this patient, are identified, which expands the genetic understanding of this condition.