Isolated autosomal recessive renal magnesium loss in two sisters.

A familial autosomal recessive form of isolated renal magnesium loss is presented. Two children in this family suffered from convulsions unrelated to hypomagnesemia. Magnesium infusion studies revealed a lowered threshold but a normal tubular maximum for magnesium. In contrast to two families with the autosomal dominant form of isolated renal magnesium wasting, the calcium excretion in the urine was normal.