Occurrence of renal tubular dysfunction in lupus nephritis

We prospectively evaluated 30 patients who presented with active systemic lupus erythematosus (SLE) for the presence of tubular abnormalities. All patients fulfilled the American Rheumatology Association criteria for SLE. When appropriate, a renal biopsy was performed. Of the 30 patients studied, 12 had no abnormal tubular study results, whereas 18 patients had some form of defect in the handling of potassium, sodium, or hydrogen ions. Eight patients had distal renal tubular acidosis (dRTA) due to an isolated proton secretory defect. Five had dRTA of the gradient or acid back-leak type. Two had an unresponsive voltage-dependent form of dRTA; one had a responsive voltage-dependent form of dRTA. One individual had hyporeninemic hypoaldosteronism and one had dRTA plus hypoaldosteronism. Clinically, patients with the abnormal tubular study results more often presented with nephritis or nephrotic sediment, peripheral edema, or anemia. Renal biopsies failed to demonstrate any difference in glomerular histologic findings and calculated activity, chronicity, or interstitial indexes. We conclude that SLE may be associated with a variety of tubular defects.