Document Type

Conference Proceeding

Publication Date

5-1-2026

Abstract

Fibrillary glomerulonephritis (FGN) is a rare primary glomerular disease characterized by the organized deposition of nonamyloid, randomly arranged fibrils within the mesangium and glomerular basement membrane. While FGN is frequently associated with malignancies and chronic infections, its association with the autoimmune spectrum is emerging as a critical clinical entity. Specifically, the relationship between DNAJB9-positive FGN and discoid lupus erythematosus (DLE) is exceedingly rare, as renal manifestations in lupus patients are typically attributed to immune-complex-mediated lupus nephritis. We present the case of a 67-year-old female with a longstanding history of DLE, manifesting as cutaneous lesions on the extremities and scalp with scarring alopecia. She presented to the nephrology clinic with newly diagnosed Stage 3 Chronic Kidney Disease (serum creatinine 1.6 mg/dL) and neurological symptoms, including slurred speech and numbness. Laboratory evaluation revealed a random urine protein-to-creatinine ratio (UPCR) of 0.2 g/g, consistent with sub-nephrotic range proteinuria, and microscopic hematuria. Notably, systemic serological markers were quiescent, with negative anti-dsDNA and normal C3 and C4 levels. A kidney biopsy demonstrated glomerular architecture consistent with FGN. Definitive diagnosis was confirmed via immunohistochemical staining strongly positive for DNAJB9, with no histological evidence of concurrent lupus nephritis. The intersection of FGN and the lupus spectrum presents a complex diagnostic landscape. While we have reports that describe FGN coexisting with active immune-complex-mediated lupus nephritis, recent literature highlights a divergent phenotype. They have introduced patients with lupus-associated rashes or systemic involvement who develop DNAJB9- confirmed FGN without any histological evidence of concurrent lupus nephritis. This phenomenon is further supported by historical observations of FGN in patients with remote discoid lupus or limited scleroderma suggesting that a chronic autoimmune milieu may serve as a catalyst for fibrillar deposition independent of traditional lupus-mediated pathways. In our patient, the absence of hypocomplementemia and the presence of sub-nephrotic proteinuria further distinguish this pathology from the typical presentation of lupus nephritis. In conclusion, this case illustrates that DNAJB9-positive FGN should be considered in the differential diagnosis of chronic kidney disease in patients with discoid lupus, even when proteinuria is sub-nephrotic and systemic serologies are negative. The presence of DLE may represent an under-recognized autoimmune environment predisposing patients to fibrillar glomerular injury rather than traditional lupus nephritis. Recognition of this association is essential to ensure accurate diagnosis and appropriate management, emphasizing that the utilization of DNAJB9 staining remains the definitive tool for preventing the mischaracterization of renal injury in patients with cutaneous lupus.

Comments

American College of Physicians Michigan Chapter and Society of Hospital Medicine Michigan Chapter 2026 Resident and Medical Student Day, May 1, 2026, Troy, MI

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