Kidney involvement in primary Sjögren's syndrome.

Kidney involvement is well recognized extraglandular manifestation of primary Sjögren's syndrome. The most common histopathological lesion is an interstitial lymphocytic infiltrate with tubular atrophy and fibrosis. In addition, immune complex associated glomerulonephritis has been reported in sporadic cases with primary Sjögren's syndrome. Here we present our experience on kidney involvement in 36 Greek patients with primary Sjögren's syndrome. The following routine renal laboratory tests were performed in all patients: serum creatinine, creatinine clearance, 24 hour urine protein excretion, urinalysis and plain film of the abdomen. These tests revealed two cases with nephrolithiasis and two with severe proteinuria (24 hour urine protein greater than 3.5 g). Kidney histology in the patients with proteinuria was compatible with membranous and membranoproliferative glomerulonephritis respectively. In fifteen randomly selected patients urinary acidification was studied before and after acute acid loading test (oral administration of NH4Cl). Renal tubular acidosis was found in five patients (one with complete and four with incomplete type). Seven patients voluntarily accepted renal biopsy; five of those had mild form of interstitial nephritis. Two of these patients had renal tubular acidosis. In conclusion, renal involvement (clinical and subclinical) is commonly found in primary Sjögren's syndrome patients.