Abstract: SA-PO0773
A Diagnostic Dilemma: Lupus Nephritis and Pauci-Immune Glomerulonephritis Overlap
Session Information
- Glomerular Diseases: Lupus Nephritis, Monoclonal Gammopathy-Related Disease, and Transplantation
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Hildebrand, Hailey Victoria, University of Manitoba Max Rady College of Medicine, Winnipeg, Manitoba, Canada
- Barr, Bryce, University of Manitoba Max Rady College of Medicine, Winnipeg, Manitoba, Canada
Introduction
Lupus nephritis (LN) occurs in up to 50% of those diagnosed with systemic lupus erythematosus (SLE). It has been reported that approximately 30% of those with LN have coexisting ANCA positivity. This was initially thought to be non-pathogenic; however, there has been increasing reports of biopsy-proven LN and pauci-immune glomerulonephritis (GN) suggesting a potentially relevant association.
Case Description
A 28-year-old lady presented with a three-month history of worsening fatigue, arthralgias, and cough. Her past medical history was significant for SLE with class 4 LN diagnosed at the age of nine. At time of diagnosis, she was treated with monthly intravenous cyclophosphamide followed by mycophenolate and hydroxychloroquine. After 10 years of quiescent disease, she discontinued therapy and follow-up.
Initial investigations revealed an acute kidney injury (AKI) (creatinine 175 umol/L, baseline 40-50 umol/L), hypoalbuminemia (15 g/L), proteinuria (416 mg/mmol), and microscopic hematuria. She was started on prednisone 50mg daily for a suspected LN flare.
Further work-up displayed a strongly positive myeloperoxidase antibody (MPO), mildly elevated ANA, a negative dsDNA, and normal complements. CT imaging of the chest found extensive bilateral ground glass opacities with a bronchoscopy confirming diffuse alveolar hemorrhage (DAH). A renal biopsy revealed extensive crescentic and necrotizing injury. Immunofluorescence showed mild mesangial and capillary loop staining for immunoglobulins and C3 but was negative for C1Q. Electron microscopy found mesangial, subepithelial, and intramembranous immune complex deposits with no tubuloreticular inclusions. This was consistent with MPO-positive pauci-immune GN on a background of LN.
She was treated with one dose of cyclophosphamide followed by rituximab, and avacopan with a rapid steroid taper. Her creatinine quickly improved to 80-90 umol/L.
Discussion
LN and pauci-immune GN overlap has been described almost exclusively in woman with MPO positivity and often presents with a severe AKI, DAH, and class 4 LN. Most reports describe diagnosing both conditions concurrently; however, our case highlights that these conditions can be diagnosed in the same individual independently at different time points. Thus, it is important to have a high degree of suspicion with a low-threshold to initiate a repeat autoimmune work-up and renal biopsy in the right clinical context.