[A case of Sjögren's syndrome complicated by membranous nephropathy]

A case of Sjögren's syndrome (SjS) complicated by membranous nephropathy (MN) is presented. A 50-year-old female was admitted to Toho University Hospital because of overt proteinuria (5g/day). She had xerotic keratitis in addition to a renal disorder, and laboratory data showed positive anti-nuclear antibody (ANA) and anti-SSA antibody. The specimens from renal biopsy revealed mild thickening of the glomerular basement membrane under light microscopy, positive IgG along the capillary walls revealed by immunofluorescence, and sparse and irregular subepithelial electron dense deposits seen under electron microscopy. No interstitial changes were observed. From these findings, she was diagnosed as having SjS complicated by MN. Proteinuria gradually decreased with a reduction in serum levels of ANA and anti-SSA antibody following corticosteroid therapy. Although renal interstitial lesions occasionally develop in patients with SjS, glomerular changes, especially MN, are very rare. We suspect that immunocomplexes, such as anti-SSA antibody, revealed in SjS patients could be responsible for the glomerular lesions, leading to MN.