Interstitial nephritis in patients with systemic lupus erythematosus: a manifestation of concomitant Sjögren's syndrome?

In order to estimate the frequency of functionally relevant tubular damage in SLE patients we used the presence of overt renal tubular acidosis as an indicative parameter of interstitio-tubular damage in a cohort of 109 SLE patients who were well characterized for potential Sjögren's syndrome. Only two patients had overt renal tubular acidosis and interstitial nephritis without major glomerular involvement. Both patients, aside from having systemic lupus erythematosus, had a number of clinical features of concomitant primary Sjögren's syndrome. Based on the results obtained and the analyses of previously published cases, we put forward the hypothesis of simultaneous primary Sjögren's syndrome as the prevailing associative factor for the rare occurrence of isolated interstitial nephritis in SLE.