Renal tubular acidosis and vasculitis associated with IgE deposits in the kidney and small vessels

We report a woman with a history of allergies, polyuria, polydipsia, protei nuria, renal loss of electrolytes, renal tubular acidosis, nephrocalcinosis , and palpable purpura. A proximal defect was excluded by a normal bicarbon ate reabsorption curve, and a distal tubular defect was shown because urine pH did not decrease to less than 6.4 despite ammonium chloride-induced sys temic acidosis. Moreover, furosemide failed to improve urinary acidificatio n. Urine-to blood PCO2 gradient was less than 14 mm Hg, although the urine bicarbonate level reached values as high as 89 mEq/L. Combining bicarbonate and neutral phosphate infusions increased the urine-to-blood PCO2 gradient to only 20 mm Hg. These subnormal PCO2 gradient Values point to proton-pum p dysfunction in the collecting tubule. Histological evidence of tubulointe rstitial disease accompanied the tubular defects. The striking histological feature was the presence of immunoglobulin E (IgE) deposits in glomeruli, tubuli, and vessels. Concurrent with these findings, she had high serum IgE titers and CD23 levels. IgE antibodies from her serum were reactive agains t human renal tubuli, with binding to two regions that matched two differen t proteins present in cortex and medulla. One of these proteins corresponde d to carbonic anhydrase II (31 kd); the second, to an unidentified protein that seems attached to cell membranes. We suggest that these IgE antibodies could have had a pathogenic role in this patient's glomerular, tubular, an d small-vessel disease. (C) 2000 by the National Kidney Foundation Inc.