Magnesium deficiency as a cause of hypocalcemia in the CHARGE association

To discover the mechanism of hypocalcemia in a patient with the CHARGE (coloboma, heart disease, atresia choanae, retarded growth and development, genital hypoplasia, and ear anomalies) association.

Chemical and metabolic studies of serum, urine, stool, and muscle specimens.

A university hospital affiliated with a municipal hospital.

One patient with the CHARGE association and refractory hypocalcemia.

Serum calcium level was 0.91 mmol/L (reference range, 2.20 to 2.58 mmol/L) and serum magnesium level was 0.34 mmol/L (reference range, 0.80 to 1.20 mmol/L) prior to any therapy. After parenteral calcium and magnesium therapy, hypocalcemia persisted (1.46 mmol/L), while the serum magnesium level was 0.84 mmol/L. A needle biopsy of skeletal muscle tissue for the magnesium content confirmed a total magnesium deficiency despite normomagnesemia (muscle magnesium content, 517 micrograms/g [reference range, 800 to 1100 micrograms/g]). Magnesium deficiency was secondary to secretion of magnesium into the gastrointestinal tract (with a daily magnesium intake of 190 mg, a 24-hour nondiarrheal fecal excretion of magnesium was 2019 mg/kg [reference range, < 1000 mg/kg of stool weight]).

Hypocalcemia was corrected only after 7 weeks of continual parenteral magnesium supplements to replenish the tissue magnesium deficiency.

Patients with the CHARGE association often have hypocalcemia. Magnesium deficiency (with or without hypomagnesemia) is a cause of the hypocalcemia in at least one patient and may prove of significance in others.