[Renal involvement in primary Sjögren's syndrome: a clinicopathological study of 26 cases].

Previous study suggested that renal involvement in primary sjögren's syndrome (SS) was rare and renal damage in SS cases has not been reported in Chinese literature. In this study the clinical and pathological features in 26 primary SS patients (23 female and 3 male, with an average age of 40.9 years) were analyzed. The spectrum of renal disorders in these patients was as follows: renal tubular acidosis (20/26), hypokelemia (18/26), hypocalcemia (14/26), mild proteinuria (less than 1.5 g/d, 12/26), massive proteinuria (more than 1.5 g/d, 9/26, including 5 nephrotic syndrome), and renal insufficiency (5/26). Light microscopy (LM) might show acute or chronic interstitial nephritis (IN, 10/26), or IN accompanied with focal glomerulonephritis (FGN, 4/26), focal segmental glomerulosclerosis (FSGS, 4/26), membranous nephropathy (MN, 3/26), diffuse mesangial proliferative glomerulonephritis (MePGN, 1/26) and membranoproliferative glomerunephritis (MPGN, 1/26) in these SS patients. A variable degree of interstitial lesion was also noted in all patients with glomerular damage. Immunofluorescent examination revealed deposits of IgG (9/24), IgA (8/24), IgM (7/24), C3 (10/24) and C1q (2/24) in granular distribution on the glomerular basement membrane (GBM) or focal masangium and focal deposits of IgG and C3 (7/24) on the tubular basement membrane (TBM). These results suggested that renal tubular acidosis is the most common finding in Chinese SS patients with renal involvement, but glomerular damage is not uncommon. Although IN was the major pathological manifestation in SS patients, FGN, FSGS, MN, MePGN and MPGN might also be found. The exact incidence of secondary glomerular disease in primary SS needs to be studied further.