Familial Hypomagnesemia With Hypercalciuria and Nephrocalcinosis in a 7‐Year‐Old Girl: A Case Report

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive renal tubular disorder, caused by mutations in the Claudin-16 or Claudin-19 genes. It is characterized by renal wasting of calcium and magnesium, bilateral nephrocalcinosis, and progression to kidney failure eventually. We had a pediatric patient with hypomagnesemia, hypercalciuria, and nephrocalcinosis with the presence of a novel missense variant of c.175C>T (p.Arg59Cys) in the CLDN16 gene on whole exome sequencing (WES). This variant falls in the category of variants of uncertain significance as per the American College of Medical Genetics and Genomics guideline. MutationTaster, Sorting Intolerant From Tolerant, and Combined Annotation-Dependent Depletion support its deleterious effect, putting it into the pathogenic category. The variant found in our case is compatible with the patient phenotype. WES is a powerful tool to confirm clinical, biochemical, and radiological diagnoses in cases of rare genetic disorders, like FHHNC.