Primary infantile hypomagnesaemia: outcome after 21 years and treatment with continuous nocturnal nasogastric magnesium infusion

Primary infantile hypomagnesaemia is an infrequent cause of neonatal hypoca lcaemic seizures but one that responds well to magnesium supplementation. W e describe a 22-year-old male, first reported at 4 months of age, who is cu rrently free of neurological deficit but has suffered from intermittent hyp omagnesaemic tetany and chronic diarrhoea due to large oral magnesium suppl ements. Hypothesizing that modest hypercalcaemia might prevent the tetany, we conducted a trial of 5 mu g/day 1,25(OH)(2)D-3 over 5 days. Despite the resultant increase in calcium, he developed tetany with the reduction of ma gnesium intake and decline of serum magnesium from 0.63 to 0.39 mmol/l (nor mal > 0.65 mmol/l). After 1,25(OH)(2)D-3 was stopped and the parenteral mag nesium injections suspended, 33% of his usual oral supplement was given ins tead by continuous nasogastric infusion and serum magnesium rose to 0.60 mm ol/l. This regimen was better tolerated because of decreased gastrointestin al side-effects and freedom from parenteral injections. We observed that 1, 25(OH)(2)D-3 supplements do not promote magnesium retention nor does the re sultant hypercalcaemia prevent hypomagnesaemic tetany. Conclusion Continuous nocturnal nasogastric infusion may be considered in l ieu of parenteral therapy in primary infantile hypomagnesaemia.