Familial Hypomagnesemia, Hypercalciuria and Nephrocalcinosis with Novel Mutation

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive disorder that is caused by mutation in genes coding for tight junction proteins claudin-16 and claudin-19. It is characterized by renal wasting of magnesium and calcium associated with the development of nephrocalcinosis and renal stones by early childhood. Most of them progress to end-stage renal failure by the second or third decade. Here, we report two siblings with FHHNC, who presented with nephrocalcinosis without any extrarenal manifestations, one of them having novel homozygous nonsense mutation in claudin-16 (CLDN16) (c.620G>A, p. Trp207Ter). Both were treated with dietary changes, hydrochlorothiazide, potassium citrate, and magnesium supplementation. FHHNC is a rare cause of nephrocalcinosis, and we believe that it should be considered in the presence of nephrocalcinosis with hypercalciuria and hypomagnesemia.