Isolated familial hypomagnesaemia with novel neurological features: causallink or chance concurrence?

We report a patient with isolated familial hypomagnesaemia with hypocalciur ia, a rare congenital disorder of magnesium metabolism. During adolescence the patient developed neurological and ophthalmological features not hither to reported in this condition, including seizures, myoclonus, and retinal p igmentary degeneration. These suggested the phenotype of mitochondrial dise ase, which has been occasionally reported in association with hypomagnesaem ia, but subsequent investigations of mitochondrial function were normal. Th e pathogenesis of this unusual neurological and ophthalmological syndrome t herefore remains uncertain.