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Kidney Week

Abstract: TH-PO708

Primary Sjögren Syndrome (pSS) with PLA2R-Associated Membranous Nephropathy (MN)

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • He, Mingyue, Temple University Hospital, Philadelphia, Pennsylvania, United States
  • Lee, Iris J., Lewis Katz School of Medicine at Temple University, Philadelphia, Pennsylvania, United States
Introduction

pSS is an autoimmune disorder characterized by lymphocytic infiltration of exocrine glands. Renal involvement occurs in 5% of pSS cases. The prevalent renal pathology associated with pSS is tubulointerstitial nephritis, with less frequent glomerular manifestations, mainly membranoproliferative glomerulonephritis. pSS is also a recognized cause of secondary MN. Herein, we present a rare case of co-occurrence of pSS and primary MN with negative serum PLA2R antibody (Ab) but positive tissue PLA2R Ab.

Case Description

A 27-year-old female with a history of pSS on plaquenil was referred to a Nephrology clinic for subnephrotic proteinuria of 1.5 gm. Urinalysis revealed no microscopic hematuria. Her creatinine was 0.54 mg/dl with no evidence of renal tubular acidosis or nephrolithiasis. Immunological markers including ANA, dsDNA, and serum PLA2R Ab were negative. Complements were normal. HIV, HBV, and HCV tests were negative. Kidney biopsy showed MN with positive immunofluorescence for IgG, C3, and PLA2R. One year later, her proteinuria decreased to 0.47 gm with preserved renal function without treatment. Her serum PLA2R Ab remained negative.

Discussion

This case poses a diagnostic challenge as to whether the observed MN is primary or secondary to pSS. Serum PLA2R Ab is associated with MN development and has high sensitivity (78%) and specificity (99%) for primary MN. Although PLA2R Ab detection has been reported in secondary MN cases such as sarcoidosis (55%), it is largely absent in rheumatic disease-associated MN, especially lupus MN (<5%). The absence of serum PLA2R Ab in this case aligns with the “kidney as sink” hypothesis, proposing that early-stage disease may show negative serum levels due to high Ab affinity for tissue antigens. Despite having persistent negative serum PLA2R Ab levels, our patient demonstrated positive tissue PLA2R Ab staining. Moreover, PLA2R Ab levels are also indicative of disease prognosis. In our case, the patient, with persistently negative serum PLA2R Ab, exhibited a significant spontaneous reduction in proteinuria. Her remission occurred in the absence of any pSS therapy, suggesting a coincidental occurrence of MN and pSS. Our case highlights that primary MN can coexist with other autoimmune diseases, emphasizing the need to distinguish primary from secondary MN due to potential differences in management strategies, where PLA2R Ab detection can be insightful.