Use of a subcutaneous magnesium pump in a patients with combined magnesiumtransport defects

History and admission findings: A 28-year-old man, known to have abnormal i ntestinal magnesium absorption, presented with recurrent cerebral seizures. Despite daily intravenous sulphate infusions, magnesium concentration rema ined inadequate. Physical examination was unremarkable. Investigations: Serum magnesium concentration was markedly reduced to 0.48 mmol/l. The parenteral magnesium tolerance test indicated reduced enteric m agnesium absorption of < 20%. Absolute magnesium concentration in 24-hour u rine was normal at 6.3mmo1/24 h, but high in proportion to the hypomagnisae mia. All other laboratory data were within normal limits. Treatment and course: In addition to the known intestinal malabsorption the patient also had isolated renal loss of magnesium. It was only by continuo us magnesium infusion with a recently developed portable subcutaneous pump system that normal serum magnesium concentrations were attainded and all sy mptoms disappeared. Conclusion: This patient has combined magnesium transport defects, which co uld not be effectively treated by conventional methods, but required contin uous magnesium infusion with an indwelling subcutaneous infusion pump. This case serves as an example of the way in which subcutaneous infusion can pr ovide physiological substitution of electrolytes.