Biochemical features of dietary chloride deficiency syndrome: a comparative study of 30 cases.

The diagnosis in one infant of a severe state of chloride deficiency after ingesting a diet consisting exclusively of a modified cow milk formula containing only 0.5 mEq/100 kcal chloride ion led to the identification of 30 additional infants (age 2.6 +/- 0.7 months) fed the same commercial formula. The total absence of chloride in the urine was used as a biochemical index of subclinical dietary chloride deficiency. Serum and urine values were studied at diagnosis and 10 to 12 days after chloride replenishment, and compared statistically with the values obtained in a control group of 40 infants (age 2.8 +/- 1.2 months) fed exclusively a different modified formula containing an adequate chloride concentration. The outstanding laboratory abnormalities noted in the infants ingesting a low chloride formula were hypochloremia and metabolic alkalosis. Mean serum concentrations of potassium, urea, creatinine, and uric acid were in the normal range, but group values were statistically different from normal. A previously unreported finding was the demonstration of a significant elevation in the serum concentrations of calcium and phosphate and in the urinary excretions of calcium and magnesium, which persisted after almost complete recovery of the remaining biochemical disturbances. These results indicate the potential risk of nephrocalcinosis after dietary chloride deficiency.