Most CLDN16 and CLDN19 variants identified in FHHNC patients are missense mutations found in homozygous or compound heterozygous state (Claverie‐Martin et al., 2015; Prot‐Bertoye & Houillier, 2020). The gene discussed is CLDN19; the disease is familial primary hypomagnesemia with hypercalciuria and nephrocalcinosis.