#4323 A RARE CASE OF MEMBRANOUS NEPHROPATHY AS THE INITIAL PRESENTATION OF SJöGREN SYNDROME
Authors: Natarajan Hariharasudan , Maryam Bibi , Shrikhande Aditya , Ahmad Zahid B 
Published: June 2023

Abstract

Introduction
Primary Sjögren's syndrome (pSS) is an autoimmune disorder characterized by lymphocytic infiltrates in exocrine glands, most commonly manifesting as dry eyes and mouth. Even though extra glandular involvement can occur in Sjögren, renal involvement is rare. It affects less than 10% of the patient population, with tubulointerstitial nephritis being the usual presentation. Glomerular involvement and, in particular, membranous nephropathy are not commonly encountered. We describe a rare case of membranous nephropathy as the initial presentation of Primary Sjögren's syndrome.

Case history
A 21-year-old female with a history of sickle cell trait presented to our emergency department with one week history of anasarca. Vital signs were unremarkable, and the physical exam was significant for a 2+ pitting edema of bilateral upper and lower extremities. Initial investigation revealed acute kidney injury (Creatinine 2.9 mg/dl from normal baseline), nephrotic range proteinuria of 6 grams on 24-hour urine collection, and hypoalbuminemia (serum albumin 1.5 mg/dl). Immunological workup showed positive ANA (speckled), strongly positive anti-SSA, borderline elevated anti-SSB, negative anti-PLA2R, negative cryoglobulins, negative anti-dsDNA, and negative anti-Smith antibody (Figure 1). Renal biopsy (Figure 2) revealed membranous nephropathy with acute tubular necrosis (ATN). PLA2R staining was negative. We attributed acute kidney injury to ATN and proteinuria to membranous nephropathy. Negative serologies and renal biopsy findings ruled out systemic Lupus. The patient was therefore diagnosed with membranous nephropathy secondary to pSS. The patient was started on Mycophenolate mofetil and steroid taper with an improvement of proteinuria and anasarca and currently follows at our clinic.

Discussion
Glomerular involvement is rare, and when involved, it is membranoproliferative glomerulonephritis (MPGN) associated with B-cell activation and positive cryoglobulins. Membranous nephropathy is rare with primary Sjögren syndrome. In our patient, a negative anti-PLA2R goes against primary membranous nephropathy. A negative anti-dsDNA and anti-Smith and biopsy findings essentially rule out Lupus nephritis, leaving Sjögren induced secondary membranous nephropathy as the most likely diagnosis. A literature search revealed few described cases of membranous nephropathy as the presenting feature of pSS with later development of sicca symptoms and progression of renal disease to MPGN. Interestingly, our patient had no sicca symptoms at the presentation time. Occult salivary gland involvement has been described in some of these patients; however, our patient deferred salivary gland biopsy. The management of renal disease in pSS has yet to be well described because of its rarity. Rituximab has shown the most benefit in patients with pSS who have positive cryoglobulins and associated MPGN. Steroids and mycophenolate mofetil (MMF) are other possible agents that can be tried. Given that experience, we started on steroids and MMF with an excellent response to treatment indicated by improvement in proteinuria.

Conclusion
This case adds to the limited available literature on membranous nephropathy as the initial manifestation of pSS. Although the European Alliance of Associations for Rheumatology (EULAR) criteria strongly emphasizes sicca symptoms and glandular involvement in pSS, the possibility of a small subset of pSS patients who present with early renal involvement with latent glandular findings needs to be recognized.