Fibrillary Glomerulonephritis: A Rare Glomerulonephritis with No Definitive Treatment

Introduction: Fibrillary glomerulonephritis (FGN) is an uncommon disorder, present in 0.5-1.4% of kidney biopsies. It is mostly seen in Caucasians of 50-60 years of age. It was initially thought to be idiopathic; however, an association with autoimmune disease, malignancy, and HCV infection has been proposed based on recent studies. It typically presents with hematuria, proteinuria, renal function impairment, HTN, and monoclonal gammopathy. For the diagnosis it is required the demonstration of randomly oriented,straight, non-branching, fibrillary deposits with a mean diameter of 20 nm in the mesangium and glomerular capillary walls without microtubule formation and Congo red stain negative. The specific biomarker DNAJB9 can be detected through immunohistochemical stain. Case Description: A 65-year-old man with medical history significant for lymphoma, tonsillar cancer, prostate cancer, treated HCV, and alcohol use disorder was admitted to the ICU due to alcohol intoxication and pneumonia. He was found to have AKI with microscopic hematuria. His renal function had some improvement initially, with gradual worsening posteriorly, and persistent microscopic hematuria with grade A3 microalbuminuria. He tested negative for ANA, MPO, PR3, anti-GBM, Syphilis, HIV, hepatitis B; C3 and C4 levels were normal. The renal pathology results showed moderate IFTA of 40%, mesangial IgM-dominant immune complex deposition, positive staining for DNAJB9, negative Congo red staining, and haphazardly arranged fibrils within mesangial regions, focally infiltrating the entire width of the GBM, with texture suggestive of fibrillary glomerulonephritis, which was more prominent than the IgM deposition. These results were consistent with FGN. He was found to have a biclonal IgG spike on SPEP, which did not correlate with the findings of IgM deposition. Bone marrow biopsy was normocellular. Cryoglobulin screening was positive. The patient was started on prednisone and ACE-i. His renal function improved but did not return to baseline. Discussion: Currently, there are no definite treatment guidelines for FGN, and the efficacy of antiproteinuric therapy is unclear. The majority of patients still progress to ESKD, being 40-50% of cases within 2-6 years. Due to the rarity of this condition, further research isneeded for better understanding of the disease process and improvement of treatment outcomes.