[Familial congenital hypomagnesemia revealed by neonatal convulsions].

Congenital hypomagnesemia is a rare disease, with an impact on cognitive and neurological development. We report on three familial cases of congenital hypomagnesemia, two boys and one girl who belong to the same consanguineous family. They all presented neonatal seizures and a psychomotor developmental delay. Cerebral computed tomography showed cerebral atrophy and calcifications in one case and magnetic resonance imaging found predominant cerebellar atrophy in the two other cases. All three patients also had hypocalcemia, hyperphosphoremia, and hypomagnesemia. The parathyroid hormone blood level was low in two cases and normal in the third. One 7-month old patient died. The others received a supplementation of calcium and magnesium, which normalized calcemia, phosphatemia but not magnesemia, which remained low despite high doses. They have both developed cognitive and behavioral impairments.