ABSTRACT
Nutritional deficiencies are common in adolescent children and include deficiencies of both micro- and macronutrients. Magnesium is an important mineral that is essential for maintenance of numerous electrophysiological and biochemical processes in the body. We report an adolescent girl who developed an episode of syncope with first degree heart block on electrocardiography and run of multifocal atrial ectopics on 24 h holter monitoring. Serum magnesium was found to be low with decreased urinary magnesium excretion. There were no other electrolyte abnormalities. Structural heart disease was ruled out by a normal echocardiogram. The rhythm changes were attributable to nutritional hypomagnesemia and were promptly reversed on correcting the hypomagnesemia