A Woman with Systemic Lupus Erythematosus (SLE) and Nephritis: Things Are Not Always as They Seem!

Introduction: We present a woman with SLE and biopsy-proven lupus membranous nephritis 37 years ago. She wsas rebiopsied for evaluation of progressive renal disease with proteinuria and microscopic hematuria and was now found to have fibrillary glomerulonephritis (FGN) with mesangial lupus nephritis. This case highlights the rare association of FGN with autoimmune disease. Case Description: A 65 yo woman presented with rashes, arthralgias and positive serology and was diagnosed with SLE in 1985. In 1988 a kidney biopsy done for evaluation of proteinuria (3.0 g/24 hrs) demonstrated membranous lupus nephritis. She was treated with high dose prednisone and entered a remission. The prednisone was tapered over several yrs but she remained on hydroxychloroquine. In 2005 she was diagnosed with Sjogren's syndrome (SS). The SCr remained stable at 0.8 mg/dl and she remained in remission until 2024 when the SCr was 1.5 mg/dl, the UPC was 1.2 g/g and a UA had 2+ protein with 11-30 RBCs/hpf. In early 2025 the SCr was up to 1.9 mg/dl, the UPC was 1.1 g/g and she continued to have microscopic hematuria. Serologic evaluation demonstrated normal C3 & C4 levels, a negative dsDNA antibody but the SSA & SSB were elevated (>8.0 AI). Due progressive renal disease with proteinuria and microscopic hematuria, she underwent a renal biopsy which demonstrated DNAJB-9 positive FGN involving the mesangium and glomerular capillary walls and mesangial lupus nephritis with full house immunoflourescence and electron dense depositis in the mesangium. Discussion: FGN is a rare form glomerular disease, seen in less than <2% of native kidney biopsies. The diagnosis of FGN is now made possible by the presence of DNAJB9 on immunostaining. Most cases of FGN are idiopathic with 15% associated with hepatitis C and rarely, <15% of cases, associated with autoimmune disease (SLE, SS and RA). Our case is unusual and highlights the potential for the evolution to FGN in pts with long-standing lupus nephritis. This underscores the value of repeat biopsies in pts with SLE and progressive renal disease with proteinuria and an active urine sediment. While FGN is a progresssive disorder and there are no proven treatments for idopathic FGN, pts with autoimmune disease and FGN may respond to immunosuppressive therapy. Thus, the finding of FGN in patients with autoimmune disease has important prognostic and therapeutic implications.