PERMEABILITY DEFECT WITH BICARBONATE LEAK AS A MECHANISM OF IMMUNE-RELATED DISTAL RENAL TUBULAR-ACIDOSIS

We present a 15-year-old girl with distal renal tubular acidosis (dRTA ) appearing in what is probably a very early stage of primary Sjogren' s syndrome. On the basis of tests evaluating renal handling of H+, we attempt to explain the mechanism of the urine acidification disorder. The inability to decrease urinary pH during systemic acidosis, togethe r with the normal increase of urinary carbon dioxide partial pressure (pCO(2)) values after sodium bicarbonate and neutral phosphate loading , suggest a gradient-type dRTA. The inability to lower urinary pH in r esponse to furosemide, accompanied by markedly increased urinary excre tion of NH4, HCO3, Na, and K, points to a collecting tubule permeabili ty disorder with bicarbonate leak to the tubular lumen. This patient h ad never been exposed to amphotericin B. To our knowledge, immune-rela ted dRTA as a result of a gradient defect with bicarbonate leak into t he tubular lumen has not been described. (C) 1998 by the National Kidn ey Foundation, Inc.