Renal Spectrum of Sjögren’s Syndrome: A Case of Secondary Membranous Nephropathy

Abstract

Sjögren’s syndrome (SS) is a systemic autoimmune disease primarily affecting exocrine glands, but with potential multisystem involvement. Renal involvement in Sjögren’s syndrome are uncommon and mostly presenting as tubulointerstitial nephritis and less frequently with glomerular involvement. We report a case of a 19-year-old female who was diagnosed to be a case of primary Sjögren’s syndrome who presented with nephrotic-range proteinuria, anasarca, and acute kidney injury severe enough to require renal replacement therapy. She also had classical sicca symptoms, arthralgia, and immunology work up was positive for anti nuclear antibody,  anti-SSA and anti-SSB confirming the presence of Sjögren’s syndrome The patient’s EULAR Sjögren's syndrome disease activity index (ESSDAI) score was 10 based on the involvement of glandular(xerostomia), renal (proteinuria and renal dysfuction) and articular domains (arthralgia without synovitis).Despite moderate ESSDAI score, owing to the presence of renal dysfunction and proteinuria ,renal biopsy was performed which demonstrated membranous nephropathy with diffuse capillary wall thickening and granular IgG1/IgG4 deposition. Immunohistochemistry and serology were negative for known membranous nephropathy antigens, including PLA2R, THSD7A, NELL-1, and EXT1, supporting a diagnosis of secondary membranous nephropathy associated with Sjögren’s syndrome. Treatment with corticosteroids and mycophenolate mofetil resulted in significant improvement in renal function and proteinuria and the patient became dialysis-independent. This case highlights an unusual renal manifestation of Sjögren’s syndrome in a young patient and signifies the importance of renal biopsy for accurately diagnosing renal involvement, even when systemic disease activity score falls in moderate category as per ESSDAI. It also raises the possibility of yet unidentified antigenic targets in Sjögren’s syndrome–associated membranous nephropathy.