Is That Really the Result of the Kidney Biopsy? Fibrillary Glomerulonephritis Associated with B Cell Lymphoma

Introduction: Fibrillary glomerulonephritis (FGN) is a rare glomerular disorder characterized by randomly arranged fibrils in the glomeruli which consist of a complex formation of antibodies and antigens. FGN is associated with lymphoproliferative disorders, solid neoplasms and autoimmune diseases. Kidney biopsy is critical for diagnosis, fibrillary deposits often test positive for DNAJB9, and Congo red staining is absent. Case Description: 77 y/o Asian M with past medical history of recently diagnosed B-Cell lymphoma receiving chemotherapy with R-CHOP, HTN, chronic smoker, BPH and CKD stage 3 presented with non-oliguric AKI for outpatient evaluation. Labs remarkable for Scr 4.14 mg/dL (baseline 1.8-2.0 mg/dL), BUN: 83 mg/dL, K: 6.3, U/A with proteinuria/RBC +, UAPCR: 2.9 gm and negative serology workup includying cryoglobulins, C3/C4 and others. Renal US with no hydronephrosis and present of bilateral renal cysts. Given patient with no clear etiology of nephrotic syndrome and acute renal failure with broad differential diagnosis secondary to patient underlying chronic medical conditions, renal biopsy was performed. Findings with diffuse positivity for DNAJB9 in immunohistochemistry, without evidence of cellular crescents or active glomerulitis confirm the diagnosis of Fibrillary GN in addition to moderate-to-advanced chronic changes of the parenchyma. Due to above mentioned renal biopsy findings patient continues treatment for B-Cell lymphoma with completion of 4-cycles of R-CHOP. Patient underwent mechanical ventilation due to COPD exacerbation. Unfortunately, despite treatment and supportive measures patient expired. During chemotherapy treatment patient with persistent stable creatinine levels and no requirements of renal replacement therapy. Discussion: Recent advances have enhanced the understanding of FGN's pathogenesis, although it remains largely unknown. Patients often present with proteinuria, hematuria, and hypertension, and the prognosis is poor, with nearly 50% progressing to end-stage renal disease within 2 to 4 years. FGN appears only in about 0.6-1% of patients undergoing native kidney biopsies. The rarity of FGN means that confirmed cases provide valuable opportunities for research, which can contribute to a better understanding of the disease and ultimately improve prognostic outcomes for future patients.