Primary hypomagnesemia with secondary hypocalcemia in an infant.

Abstract

A male infant presented at 6 weeks of age with generalized convulsions and coma associated with hypomagnesemia and hypocalcemia. Hypomagnesemia was not the result of any previously reported causes of magnesium deficiency, such as steatorrhea, excessive urinary loss of magnesium, or known endocrine disturbance. The patient was successfully treated by oral magnesium supplementation. The defect in magnesium homeostasis was still present at 3 years of age. Hypomagnesemia was considered to be due to either a specific defect in intestinal transport of magnesium or an unknown derangement of magnesium homeostasis. The defect in magnesium metabolism caused severe hypocalcemia which was promptly and completely corrected by oral or parenteral administration of magnesium salts. Thus, magnesium ion was necessary for normal calcium homeostasis. A renal biopsy showed hyalinization of some glomeruli but no prominent tubular lesions. Impairment of renal function could not be detected in the patient. Oral magnesium supplementation was necessary to maintain satisfactory levels of magnesium and calcium. This therapy cured the severe neurological disturbance and, over the 3-year period of study, the boy developed normally.