An extreme example of the neonatal form of Bartter's syndrome.

A male infant is described who had polyuria over the 4 months of his life with urine volumes exceeding 1,000 ml/kg per day, severe serum electrolyte losses, metabolic alkalosis and increased plasma renin activity (56 ng/ml per hour). He had a normal blood pressure and glomerular filtration rate when fluid replete. The urine flow rate was about 25% of the glomerular filtration rate. Renal histology showed hyperplasia of the juxtaglomerular apparatus and abnormalities of the proximal tubules. The features of this case suggest an extreme form of Bartter's syndrome presenting from the first days of life.