Breast milk is widely advocated as optimal nutrition for infants, with almost unanimous agreement regarding its benefits during the first few months of life. There is much less agreement as to the optimal duration of breast-feeding; recommendations vary from 4 to 10 months.1,2 There is also very little information available about long-term (>6 months) changes in breast milk electrolytes, especially chloride. We describe three exclusively breast-fed infants who had hypokalemic, hypochloremic metabolic alkalosis similar to chloride deficiency syndrome at 7, 8, and 9 months of age. Analysis of their mothers' breast milk demonstrated electrolyte deficiencies, particularly sodium and chloride. To our knowledge, this problem has not been reported in children of these ages.
Patient Reports.Patient 1. A 9½-month-old white male child presented at Brooke Army Medical Center (Fort Sam Houston, Tex) for workup of suspected Bartter's syndrome. Table 1 shows the infant's serum and urine electrolyte concentrations; serum