Magnesium deficiency as a cause of hypocalcemia in the CHARGE association.

OBJECTIVE

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.

RESEARCH DESIGN

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

SETTING

A university hospital affiliated with a municipal hospital.

PARTICIPANT

One patient with the CHARGE association and refractory hypocalcemia.

MEASUREMENTS AND RESULTS

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]).

INTERVENTIONS

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

CONCLUSIONS

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.