Abstract: SA-PO0763
When Serologies Mislead: A Case of Fibrillary Glomerulonephritis Masquerading as Drug-Induced Lupus
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
- Singh, Aditi, Johns Hopkins University, Baltimore, Maryland, United States
- Hanouneh, Mohamad, Johns Hopkins University, Baltimore, Maryland, United States
- Geetha, Duvuru, Johns Hopkins University, Baltimore, Maryland, United States
Introduction
Hydralazine-induced ANCA vasculitis and lupus overlap typically present with high titer positivity for several antibodies, often with kidney involvement. We present a case of fibrillary glomerulonephritis (GN), which was initially diagnosed as hydralazine-induced ANCA vasculitis, leading to the diagnosis of occult breast cancer.
Case Description
A 66-year-old female with a history of hypertension and CKD with baseline serum creatinine (sCr) of 1.5 mg/dl presented with AKI (sCr 3 mg/dl), microscopic hematuria (25/hpf), and proteinuria (7.4g). Serologies revealed positive antibodies, including ANA (1:320), p-ANCA (1:1280), anti-histone (9.5 U), MPO (28 AU/ml), and PR3 (63 AU/ml). Hydralazine was considered the likely culprit for drug-induced vasculitis and was discontinued. Kidney biopsy revealed normocellular glomeruli with mesangial expansion; immunofluorescence with granular mesangial staining for IgG, IgM, C3, kappa, and lambda, with IgG subclass positive for IgG4. She received pulse methylprednisolone and transitioned to prednisone plus mycophenolate mofetil with suspicion for hydralazine-induced lupus based on serologies. Electron microscopy demonstrated deposits with fibrillar substructure averaging 14 nm in size (Figure 1), and immunostaining for DNAJB9 was positive, leading to the diagnosis of fibrillary GN. A malignancy screen identified a breast mass, and immunosuppression was discontinued. She underwent lumpectomy and axillary dissection, which showed invasive ductal carcinoma, now managed with radiation and an aromatase inhibitor. Her kidney function improved, with sCr decreasing to 2.0 mg/dL and proteinuria stabilizing at 3.0 g over 3 months.
Discussion
Fibrillary GN is commonly associated with autoimmune diseases, infections, and malignancies. In our case, hydralazine use was a red herring given the discovery of occult malignancy. Breast cancer has been strongly associated with positive antibodies as a paraneoplastic phenomenon. Our case underscores the importance of a kidney biopsy in establishing a diagnosis and highlights the limitations of serological testing.