Fibrillary Glomerulonephritis with Cellular Crescents: An Atypical Presentation of a Rare Disease

Introduction: Fibrillary glomerulonephritis (FGN) is a rare disease (0.5-1.5% of native kidney biopsies) that has gained increasing recognition in recent years. The typical presentation is either nephrotic or nephritic, with unrevealing serologic workup. Presenting serum creatinine ranges between 2 mg/dL and 3.2 mg/dL in most case reviews. Up to 50% of cases have other associated conditions (autoimmune, infection, or monoclonal gammopathy). Atypical pathologic features include cresentic FGN with focal cellular or fibrous cresents seen in 17-31% of cases. We present a case of FGN where the presentation was more acute than typically described, with cellular cresents. Case Description: 80 year old female with history of ulcerative colitis (quiescent longstanding), was initially noted to have 2+ protein on urinalysis. This quantified shortly after at 950 mg/g. Escalation of angiotension receptor blockade led to improvement at 400 mg/g -- but did rebound back to 960 mg/g. About 16 months from original presentation, proteinuria reached 1800 mg/g. Renal function remained stable with serum creatinine 1.2 mg/dL. 6 months later, serum creatinine rose to 3.0 mg/dL with urine protein creatinine ratio rising upward of 7 g/g. Kidney biopsy revealed 3+ smudgy global mesangial and glomerular capillary wall staining for IgG, kappa and lambda, with 2-3+ C3. Also, strong reactivity for DNAJB9 by immunohistochemistry supported a diagnosis of FGN. There was diffuse membranoproliferative and segmental endocapillary proliferative features with focal cresents involving 35% of the sampled cortex. Discussion: While our understanding of FGN has advanced, there are still several questions to be answered. The exact pathogensis remains elusive, as does the mechanistic role of DNAJB9. There are several atypical variants, indicating the disease's heterogeneity. Typically middle age individuals are affected, presenting with advanced renal failure. Our case illustrates a more insidious course in an elderly female who first had low grade proteinuria. This later rose to nephrotic spectrum, accompanied almost 2 years later by a sharp rise in serum creatinine -- correlating with cellular cresents on pathology. Given the poor prognosis of FGN (half of patients progress to end stage kidney disease within 2-4 years post diagnosis), an earlier index of suspicion to make the diagnosis could prove integral.