Variant of Bartter's syndrome with a distal tubular rather than loop of Henle defect

A 19-year-old normotensive patient had all of the clinical features of Bartter's syndrome: hypokalemia, elevated renin and aldosterone levels and increased excretion of prostaglandin E. In contrast to the patients described by Bartter, the patient had a normal capacity to form solute-free water, suggesting intact loop of Henle function. Baseline potassium and chloride excretion rates were higher than those observed in 5 normal subjects, but the response to intravenous chlorothiazide, a drug which acts in the early distal convolute tubule, was abnormal. While chloride excretion rose by only 61% in this patient, it increased sixfold in the normal subjects. Sodium excretion quadrupled in the controls but less than doubled in this patients. Roughly equivalent increments in potassium excretion occurred in normals and controls, suggesting that the patient's distal potassium-secretory mechanism was intact. Review of the literature indicates that whether the site of the abnormal renal tubular potassium (chloride) leak is the proximal tubule, the loop of Henle or the distal convoluted tubule, patients may achieve features indistinguishable from those previously reported as characteristic for Bartter's syndrome. If loop of Henle malfunction is required to diagnose classical Bartter's syndrome, then our patient (and several reported elsewhere) has a variant form.