Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is a progressive renal disorder characterized by excessive urinary Ca(2+) and Mg(2+) excretion. There is progressive loss of kidney function, and in about 50% of cases, the need for renal replacement therapy arises as early as the second decade of life (summary by Muller et al., 2006). Amelogenesis imperfecta may also be present in some patients (Bardet et al., 2016). A similar disorder with renal magnesium wasting, renal failure, and nephrocalcinosis (HOMG5; 248190) is caused by mutations in another tight-junction gene, CLDN19 (610036), and is distinguished by the association of severe ocular involvement. For a discussion of phenotypic and genetic heterogeneity of familial hypomagnesemia, see HOMG1 (602014).

HOMG5 is an autosomal recessive disorder characterized by severe renal magnesium wasting, progressive renal failure, nephrocalcinosis, and severe visual impairment (Konrad et al., 2006). Amelogenesis imperfecta may also be present in some patients (Yamaguti et al., 2017). For a discussion of genetic heterogeneity of renal hypomagnesemia, see 602014.