Rapidly progressive renal failure with nephrotic syndrome in a patient with type 2 diabetes mellitus: the differential of fibrillary deposits

Fibrillary Glomerulonephritis and DnaJ Homolog Subfamily B Member 9 (DNAJB9)

Fibrillary GN (FGN) is a rare glomerular disease that is diagnosed based on the presence of fibrils in glomeruli. The fibrils are typically noncongophilic, randomly oriented, and measure 12–24 nm. Traditionally, electron microscopy (EM) has been an important tool to aid in the diagnosis of FGN by identifying the fibrils and to distinguish it from other entities that could mimic FGN. However, recently DnaJ homolog subfamily B member 9 (DNAJB9) has emerged as both a specific and sensitive biomarker in patients with FGN. It allows prompt diagnosis and alleviates reliance on EM. DNAJB9 is a cochaperone of heat shock protein 70 and is involved in endoplasmic reticulum protein-folding pathways. But its role in the pathogenesis of FGN remains elusive. DNAJB9 may act as a putative antigen or alternatively it may secondarily bind to misfolded IgG in the glomeruli. These hypotheses need future studies to elucidate the role of DNAJB9 in the pathogenesis of FGN. The treatment regimen for FGN has been limited due to paucity of studies. Most patients receive combination immunosuppressive regimens. Rituximab has been studied the most in FGN and it may delay disease progression. Prognosis of FGN remains poor and 50% require dialysis within 2 years of diagnosis. Despite its poor prognosis in native kidneys, the rate of recurrence post-transplantation is low (20%) and patient as well as allograft outcomes are similar to patients without FGN.

Fibrillary glomerulonephritis presenting as crescentic glomerulonephritis

Fibrillary glomerulonephritis (FGN) is a rare primary glomerular disease that commonly presents clinically with hypertension, proteinuria, microscopic hematuria, and varying degree of renal insufficiency. Histologically, FGN can present with different patterns of glomerular injury, more commonly mesangioproliferative, membranoproliferative, and membranous nephropathy. While crescent formation has been described in some kidney biopsy series of FGN, crescentic glomerulonephritis pattern of glomerular injury has been rarely described. Optimal therapy and outcomes in FGN presenting with crescentic GN is not currently known. We report an adult patient who presented with massive proteinuria and severe renal failure. The kidney biopsy revealed crescentic FGN (C-FGN). The patient remained dialysis dependent despite immunosuppressive therapy. We also briefly review FGN, and the few reported cases of C-FGN that presented as rapidly progressive or advanced renal failure in the literature.

Fibrillary glomerulonephritis: presenting as crescentic glomerulonephritis causing rapidly progressive renal failure

We report an unusual case of fibrillary glomerulonephritis (FGN) presenting as rapidly progressive renal failure and extensive crescent formation along with linear staining of capillary walls of the glomeruli on immunofluorescence, mimicking anti-glomerular basement membrane (anti-GBM) antibody-mediated disease. Laboratory results for circulating anti-GBM antibodies were negative. The subsequent electron microscopic findings were that of presence of electron-dense deposits in the glomerular mesangium and capillary walls, comprising of non-branching fibrils with an average diameter of 16 nm consistent with a diagnosis of FGN. This case illustrates the crucial role of electron microscopy in differential diagnosis of crescentic glomerulonephritis.

The occurrence or fibrillary glomerulonephritis in patients with diabetes mellitus may not be coincidental: a report of four cases

Although clinical presentation of fibrillary glomerulonephritis is similar to most forms of glomerulonephritis, it is usually difficult to make the diagnosis. Clinical manifestations include proteinuria, microscopic haematuria, nephrotic syndrome, and impairment of renal function. A diagnosis of fibrillary glomerulonephritis is only confirmed by renal biopsy and it must comprise electronmicroscopy-verified ultrastructural findings. We report four cases between 45–50 years old with documented type 2 diabetes mellitus (T2DM) and arterial hypertension. All patients were found to have fibrils on kidney biopsy. The differential diagnosis of fibrils in the setting of diabetes mellitus is also discussed.

Fibrillary glomerulonephritis with small fibrils in a patient with the antiphospholipid antibody syndrome successfully treated with immunosuppressive therapy

BACKGROUND

Fibrillary glomerulonephritis is a rare cause of progressive renal dysfunction, often leading to the need for dialysis within a few years. The role of immunosuppressive treatment is still uncertain although this has been tried with variable success.

CASE PRESENTATION

A 56 year old woman with the antiphospholipid antibody syndrome (IgM anticardiolipin antibodies) was seen in the nephrology clinic with haematuria, proteinuria, and worsening renal function. A renal biopsy demonstrated a mesangial proliferative glomerulonephritis on light microscopy and smaller fibrils (10.6-13.8 nm in diameter) than is usual for fibrillary glomerulonephritis (typically 18-22 nm) on electron microscopy. Amyloidosis was excluded following detailed evaluation. On account of rapidly worsening renal failure she was started on cyclophosphamide and prednisolone which led to the partial recovery and stabilization of her renal function.

CONCLUSION

This case highlights the need for routine electron microscopy in native renal biopsies, where the differential diagnosis is wide and varied and the light and immunofluorescence microscopic findings may be non specific.

Glomerular mesangial fibrillary deposits in a patient with diabetes mellitus

Various systemic or primary glomerular diseases can result in deposition of fibrillary material in the glomerular tuft and may cause an important diagnostic challenge for the pathologists. Biopsy findings of a patient with type 2 diabetes is presented here in which striking fibrillary structures were identified in the mesangium by ultrastructural examination. The distinction between diabetic fibrillosis and fibrillary glomerulonephritis accompanying diabetic nephropathy is discussed in the setting of a literature review.

Fibrillary glomerulonephritis associated with crescents as a therapeutic challenge

Most cases of fibrillary glomerulonephritis (FG) terminate in end-stage renal disease within a few years. We report on two female patients (41 and 50 years old) with the diagnosis of FG associated with crescentic glomerulonephritis, a combination found in 20% to 25% of cases of FG. A broad spectrum of infectious disease and systemic immunologic disorders could be ruled out by specific assays. Both patients had severely impaired renal function, nephrotic syndrome, and hypertension. Based on the biopsy finding with necrotizing FG, treatment was started with corticosteroids and cyclophosphamide. In both patients, renal function recovered markedly within 6 months of treatment, in one case remaining stable for 3.5 years. Whether or not cyclophosphamide treatment changed the course of the FG itself or counteracted the acute crescentic process cannot be determined from these two patients. Based on these promising preliminary findings and the poor prognosis of FG, however, we recommend cyclophosphamide treatment of patients with FG and additional crescentic glomerulonephritis. For a systematic evaluation of the therapeutic options in FG, a multicenter clinical trial should be conducted.