Primary familial hypomagnesemia syndrome: a new approach in treatment.

Primary familial hypomagnesemia is a rare genetically determined disorder characterized by a selective defect in magnesium (Mg) absorption. Mutations of the transient receptor potential melastatin 6 (TRPM6) gene, which codes for TRPM6, the basic channel for intestinal Mg absorption and a new member of the transient receptor potential (TRP) family of cation channels, result in primary hypomagnesemia. Here we present a 14-year-old Turkish girl whose first symptoms manifested as neonatal tetany at 17 days old. During her follow-up, she was mainly taking high-dose oral Mg therapy. However, intravenous Mg and calcium (Ca) therapies were given during symptomatic attacks. When her requirements for Ca and Mg were increased during the pubertal growth period, which overlapped with increased loss of Mg during the summer, oral Ca and active vitamin D (calcitriol, Rocaltrol) were added. Calcitriol is needed because hypomagnesemia results in decreased production and resistance to the actions of active vitamin D, which leads to the disturbance of intracellular signal transmission. Although high-dose oral Mg is reported as a sufficient therapy in most of the patients with primary familial hypomagnesemia, addition of active vitamin D to the usual oral Mg and Ca therapy seems very useful, as in this patient.