• We were able to separate Bartter's syndrome patients into two groups: Group 1 patients are seen at a young age, with hyponatremia and episodes of extracellular volume contraction. Group 2 patients are older and most have tetany; plasma sodium values and renal sodium balances are normal. Plasma potassium values are lower and plasma renin activity and plasma magnesium levels are higher in group 1 than in group 2. It may be that all patients with Bartter's syndrome manifest the features of both groups, group 1 patients with time developing into group 2 patients. These observations have important implications in the treatment of patients with Bartter's syndrome
(Am J Dis Child 133:636-638, 1979)