TRPM7 and familial primary hypomagnesemia: Recently, mutations in TRPM7 have been linked to an autosomal dominant variant of hypomagnesemia (low serum concentrations of Mg2+).893., 894., 895. The affected patients were heterozygous for LOF point mutations in TRPM7. Apart from hypomagnesemia, the patients displayed other less prominent symptoms, including episodes of hypocalcemia (low serum concentrations of Ca2+), seizures, and muscle cramps.