Updates on the Diagnosis and Management of Fibrillary Glomerulonephritis

Fibrillary glomerulonephritis (FGN) is a rare kidney disease typically affecting individuals in middle age, frequently presenting with advanced renal failure, proteinuria, and hypertension. FGN can be associated with autoimmune diseases, hepatitis C infection, and malignancies. Its exact pathogenesis remains elusive, and the exact role of DnaJ homolog subfamily B member 9 is yet to be determined. On renal biopsy, FGN exhibits distinctive Congo-red-negative, nonbranching fibrils, approximately 20 nm in diameter. DnaJ homolog subfamily B member 9 immunohistochemical staining has become a gold standard for diagnosis. Atypical variants exist, including congophilic, monotypic, and crescentic FGN, highlighting the disease's heterogeneity. Treatment with immunosuppression, including rituximab, has shown variable success, with no standard therapy established. FGN often leads to end-stage kidney disease, with a median progression time of 2-4 years postdiagnosis. Kidney transplantation is a viable option for FGN-related end-stage kidney disease, but recurrence in transplanted kidneys is not rare.

[Latest updates on immunotactoid glomerulopathy and fibrillary glomerulonephritis]

Various hematologic malignancies can lead to renal complications. The most common of these hemopathies to affect the kidney is multiple myeloma, however an increasing number of kidney diseases are associated with other monoclonal gammopathies. It is recognized that clones in small abundance can be responsible for severe organ damage, thus the concept of monoclonal gammopathy of renal significance (MGRS) has emerged. Although the hemopathy in these patients is more consistent with monoclonal gammopathy of undetermined significance (MGUS) than with multiple myeloma, the diagnosis of a renal complication changes the therapeutic management. Preservation and restoration of renal function is possible with treatment targeting the responsible clone. In this article, we take as an example immunotactoid and fibrillary glomerulopathies, two distinct entities with different etiologies and consequently different management. Immunotactoid glomerulopathy is most often associated with monoclonal gammopathy or chronic lymphocytic leukemia, the deposits on renal biopsy are monotypic, and treatment is therefore based on clone targeting. Fibrillary glomerulonephritis, on the other hand, is caused by autoimmune diseases or solid cancers. Deposits on renal biopsy are in the vast majority polyclonal. There is a specific immunohistochemical marker, DNAJB9, and treatment is less well established.

[Fibrillary glomerulonephritis]

Fibrillary glomerulonephritis (FGN) is a glomerular disease described since 1977, with a prevalence in renal biopsies of less than 1%. It presents as renal failure, proteinuria, haematuria and hypertension in middle-aged adults. It is defined histologically, using light microscopy, which reveals organised deposits of fibrils measuring around 20nm, which are negative for Congo red staining. Electron microscopy, the first gold standard for diagnosis, has now been superseded by immunohistochemistry using the anti-DNAJB9 antibody. The discovery of this molecule has revolutionised the diagnosis of GNF, thanks to its excellent sensitivity and specificity (98% and 99% respectively). The association of GNF with hepatitis C virus, autoimmune diseases, neoplasia or haemopathy is debated. Renal prognosis is guarded, with 50% of patients progressing to end-stage renal failure within 2 to 4years of diagnosis. In the absence of randomised controlled trials, the recommended treatment is based on nephroprotective measures, corticosteroid therapy and possibly a second-line immunosuppressant such as rituximab. After renal transplantation, recovery or recurrence is possible. The pathophysiology of the disease is still poorly understood, and further studies are needed.

Glomerulopathies with Fibrillary Deposits

The glomerulopathies associated with the deposition of extracellular fibrils in the glomeruli are subdivided into Congo red positive (amyloidosis) and Congo red negative (non-amyloidotic glomerulopathies) based on Congo red staining. The non-amyloidotic glomerulopathies are divided into immunoglobulin-derived and non-immunoglobulin-derived glomerulopathies. The immunoglobulin-derived glomerulopathies: fibrillary glomerulopathy (FGn) and immunotactoid glomerulopathy (ITG) are rare glomerulopathies. The diagnosis of fibrillary-immunotactoid glomerulopathy depends on electron microscopy, which shows the presence of microfibrils in the glomeruli. The microfibrils in FGn are randomly arranged with diameters less than 30 nm. The microfibrils in ITG are larger than 30 nm with a visible lumen (microtubules), focally arranged in parallel bundles. Patients with fibrillary-immunotactoid glomerulopathy present with proteinuria (usually in the nephrotic range), microscopic hematuria, arterial hypertension, and chronic kidney disease that progresses to kidney failure over months to years. Currently, there are no guidelines for the treatment of fibrillary-immunotactoid glomerulopathy, although immunotactoid glomerulopathy could be associated with underlying hematologic disorders with the need for clone-directed therapy.

A Case of Posttransplant Fibrillary Glomerulonephritis

Fibrillary glomerulonephritis (FGN) is a rare form of glomerulonephritis, usually occurring in concurrence with other conditions such as hepatitis C, dysproteinemia, autoimmune conditions, diabetes mellitus, and malignancy. The diagnosis is made by the presence of randomly oriented fibrillar deposits with a mean diameter of 20 nm, which stain positive for IgG and C3 and are negative for congo red and thioflavin T stains. Staining for DNAJB9 (DnaJ homolog subfamily B member 9) is a recently discovered mode of diagnosis of FGN without electron microscopy. The prognosis is poor and optimal treatment is yet not clearly defined, though rituximab may be useful in FGN patients with relatively preserved renal functions. In this case report, we discuss a case of post-renal transplant patient with de novo occurrence of fibrillary glomerulonephritis.

Fibrillar glomerulonephritis in a patient with systemic lupus erythematosus with no evidence of lupus nephritis

Fibrillar glomerulonephritis (FGN) is a rare proliferative form of glomerular disease characterised by randomly oriented fibrillar deposits with a mean diameter of 20 nm. It has a rare association with systemic lupus erythematosus (SLE). We report the case of a female in her mid-50's with a 20 year history of SLE, who developed proteinuria due to FGN and had no histological evidence of lupus nephritis. She was maintained on azathioprine and prednisolone. A renal biopsy revealed randomly arranged fibrillar deposits that positively stained for DNAJB9, consistent with a diagnosis of FGN. Azathioprine was switched to mycophenolate mofetil, and the patient showed significant improvement in proteinuria. This case-based review describes the diagnosis, management and clinical outcome of FGN in association with SLE in the absence of lupus nephritis.

A Rare Case of Recurrent Immunotactoid Glomerulonephritis

Immunotactoid glomerulopathy is an uncommon cause of glomerular disease that results from deposits derived from immunoglobulins. This rare disease can occur in native kidneys and in transplant patients. They are present only in 0.5% to 1.4% of native kidney biopsies. Treatment of this disease is directed at the underlying monoclonal gammopathy, infection, and B-cell lymphoproliferative disorders. Prognosis is very guarded with 50% of people developing ESRD within five years of diagnosis. We present an interesting, rare case of recurrent immunotactoid glomerulonephritis which responded appropriately to rituximab therapy.

Fibrillary Glomerulonephritis in a Patient With Vulvar Squamous Cell Carcinoma

Fibrillary glomerulonephritis is a rare condition characterized by glomerular accumulation of non-branching fibrils, leading to hematuria, proteinuria, and hypertension. It is often associated with malignancy but has no known cause. A 66-year-old Caucasian female with a history of vulvar squamous cell carcinoma presented with one month of painless hematuria in the setting of new-onset progressive renal dysfunction and nephrotic range proteinuria. Comprehensive evaluation, including renal biopsy with staining for DnaJ heat shock protein family member B9 (DNAJB9), provided a definitive diagnosis of fibrillary glomerulonephritis. The patient initially received rituximab and prednisone therapy. Unfortunately, her renal function continued to decline over the next month, requiring re-hospitalization with initiation of hemodialysis. To our knowledge, this is the first case describing an association between vulvar squamous cell carcinoma and fibrillary glomerulonephritis.

Fibrillary Glomerulonephritis: A Great Mimicker of Rapidly Progressive Glomerulonephritis

Fibrillary glomerulonephritis (FGN) is a rare but severe kidney disease found to have non-amyloid fibrillary deposits in the mesangium and/or glomerular capillary wall. It was initially thought to be idiopathic, but recent studies show an association with autoimmune disease, malignancy, and hepatitis C infection. We report a case of a non-diabetic patient presenting with long-standing microscopic hematuria, progressive proteinuria, hypertension, and worsening kidney function. The kidney biopsy demonstrated subepithelial fibrillar deposits of size 17 mm randomly oriented with one partial cellular crescent on electron microscopy. Direct immunofluorescence showed no staining for IgG or light chains. It was weakly positive for Congo red staining with a slightly higher serum free kappa/lambda light chain ratio, but serum immunofixation showed no monoclonal protein detection. We empirically treated with rituximab but with no clear benefit or no renal recovery and eventually started on hemodialysis. FGN has an extremely poor prognosis with very few treatment options available. We report this case to emphasize the need for larger, multi-center studies for treatment approaches with collaborating and consolidating data from case reports and case series due to the rarity of the disease.

Monoclonal Gammopathy-Related Kidney Diseases

Monoclonal gammopathies occur secondary to a broad range of clonal B lymphocyte or plasma cell disorders, producing either whole or truncated monoclonal immunoglobulins. The kidneys are often affected by these monoclonal proteins, and, although not mutually exclusive, can involve the glomeruli, tubules, interstitium, and vasculature. The nephrotoxic potential of these monoclonal proteins is dependent on a variety of physicochemical characteristics that are responsible for the diverse clinicopathologic manifestations, including glomerular diseases with organized deposits, glomerular diseases with granular deposits, and other lesions, such as C3 glomerulopathy and thrombotic microangiopathy with unique pathophysiologic features. The diseases that involve primarily the tubulointerstitial and vascular compartments are light chain cast nephropathy, light chain proximal tubulopathy, crystal-storing histiocytosis, and crystalglobulin-induced nephropathy with distinct acute and chronic clinicopathologic features. The diagnosis of a monoclonal gammopathy-related kidney disease is established by identification of an underlying active or more commonly, low-grade hematologic malignancy, serologic evidence of a monoclonal gammopathy when detectable, and most importantly, monoclonal protein-induced pathologic lesions seen in a kidney biopsy, confirming the association with the monoclonal protein. Establishing a diagnosis may be challenging at times, particularly in the absence of an overt hematologic malignancy, with or without monoclonal gammopathy, such as proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Overall, the treatment is directed against the underlying hematologic disorder and the potential source of the monoclonal protein.

Clinicopathologic features and treatment outcomes of patients with fibrillary glomerulonephritis: A case series

ABSTRACT

Fibrillary glomerulonephritis (FGN) is a diverse glomerular disease with poor renal prognosis. The optimal therapeutic approach remains undetermined, as treatment outcomes vary across different studies.We retrospectively reviewed the medical data of 10 patients diagnosed with biopsy-proven FGN at our center between 2004 and 2019. Clinical and histological features, as well as therapeutic regimens and treatment response, are reported.The patients were predominantly men (2.5/1 men-female ratio) with a mean age at diagnosis of 46.5 years (IQR: 41.5-59.5). The median proteinuria and creatinine levels at presentation were 2.55 g/day (IQR: 0.4-8.9) and 1.35 mg/dl (IQR: 0.94-1.88), respectively. Four out of 10 patients presented with nephrotic syndrome, 5 patients with nephritic syndrome and 1 with isolated microscopic hematuria. Light microscopy showed mesangial proliferative (n = 7), membranoproliferative-like (n = 2), and diffuse sclerosing patterns (n = 1). Rituximab was used in 7/10 patients, either as monotherapy (n = 3) or combined with cyclophosphamide and corticosteroids (n = 4). Patients who were treated with immunosuppression had higher median levels of creatinine (1.40 mg/dl) and proteinuria (3.5 g/d) compared to those who received supportive treatment alone (0.94 mg/dl and 0.6 g/d, respectively). After a median follow-up of 30 months (IQR:18-66.5), 4 out of 7 patients (57%) treated with immunosuppression achieved a clinical response, 1 had persistent renal dysfunction and 2 patients progressed to end-stage renal disease.The present case series extends the existing literature on the clinical features and outcomes of FGN, as well as the use of rituximab-based regimens for the treatment of the disease. Further research is needed to establish the proper management of the disease.

DNA J homolog subfamily B member 9 and other advances in fibrillary glomerulonephritis

PURPOSE OF REVIEW

Fibrillary glomerulonephritis (FGN) involves ∼1% of native kidney biopsies and is characterized by glomerular deposition of fibrils larger than amyloid (12-24 nm diameter) composed of polyclonal immunoglobulin G (IgG). The recent discovery of DNA J homolog subfamily B member 9 (DNAJB9) in FGN glomerular deposits has contributed a specific and sensitive biomarker, informing morphologic classification and pathogenesis. This review will consider contemporary FGN incidence and genetics, pathogenesis, (lack of) paraprotein association, variants, treatment, and transplantation.

RECENT FINDINGS

DNAJB9 tissue assays have enabled the identification of morphologic variants and improved classification of fibrillary-like glomerular diseases. Together with paraffin immunofluorescence and IgG subclass studies, these have established that FGN is only rarely monoclonal and these patients usually do not have an monoclonal gammopathy. The discovery of DNAJB9 opens new avenues of investigation into FGN pathogenesis, especially those of the unfolded protein response. Treatment for FGN remains empiric, with some encouraging data on rituximab-based therapy. Transplantation is a good option for patients progressing to end-stage kidney disease.

SUMMARY

Advances building on the discovery of DNAJB9 in FGN should lead to long-term evolution in targeted treatment and outcome of this glomerular disease.

Treatment of fibrillary glomerulonephritis with rituximab: a 12-month pilot study

BACKGROUND

Fibrillary glomerulonephritis (FGN) is a rare type of glomerulonephritis with poor prognosis, with no known effective therapies available for treatment. The objective of the study was to evaluate the efficacy and safety of rituximab in treatment of patients with FGN and to investigate the effect of rituximab on DNAJB9 levels.

METHODS

This was a pilot prospective clinical trial in which patients with idiopathic FGN were treated with two courses of rituximab (1 g each) 2 weeks apart at the beginning and then again at 6 months. Primary outcome was defined as preservation of kidney function at 12 months with stable or increased creatinine clearance. Secondary outcome was defined as achieving complete remission (CR) defined as proteinuria <300 mg/24 h or partial remission (PR) with proteinuria <3 g/24 h and at least 50% reduction in the proteinuria. DNAJB9 levels were also measured in the serum at baseline, 6 and 12 months.

RESULTS

The creatinine clearance did not change significantly during this time, from 47.7 mL/min/1.73 m2 at baseline to 43.7 mL/min/1.73 m2 during follow-up (P = 0.15). Proteinuria declined from 4.43 (1.6-5.53) g/24 h at baseline to 1.9 (0.46-5.26) g/24 h at 12 months but did not reach significance (P = 0.06). None of the patients reached CR, and 3 of the 11 achieved PR. There was no change in the DNAJB9 levels following treatment with rituximab. The most common adverse event was nasal congestion, fatigue and muscle cramps.

CONCLUSIONS

Treatment of patients with two courses of rituximab over a span of 6 months was associated with stabilization of renal function but did not result in a significant change in proteinuria and with no change in the DNAJB9 levels.

Characteristics of patients with coexisting DNAJB9-associated fibrillary glomerulonephritis and IgA nephropathy

Background

Coexistence of fibrillary glomerulonephritis (FGN) and immunoglobulin A (IgA) nephropathy (IgAN) in the same kidney biopsy (FGN–IgAN) is rare, and the clinicopathologic characteristics and outcome of this dual glomerulopathy are unknown.

Methods

In this study, 20 patients with FGN–IgAN were studied and their characteristics were compared with 40 FGN and 40 IgAN control patients.

Results

Concurrent IgAN was present in 1.8% of 847 consecutive FGN cases and was the second most common concurrent glomerulopathy after diabetic nephropathy. FGN–IgAN patients were overwhelmingly White (94%) and contrary to FGN patients were predominantly (60%) males. Compared with IgAN patients, FGN–IgAN patients were older, had higher proteinuria, a higher incidence of renal insufficiency, and a lower incidence of microhematuria and gross hematuria at diagnosis. Six (30%) patients had malignancy, autoimmune disease or hepatitis C infection, but none had a secondary cause of IgAN or clinical features of Henoch–Schonlein purpura. Histologically, all cases exhibited smudgy glomerular staining for immunoglobulin G and DnaJ homolog subfamily B member 9 (DNAJB9) with corresponding fibrillary deposits and granular mesangial staining for IgA with corresponding mesangial granular electron-dense deposits. On follow-up (median 27 months), 10 of 18 (56%) FGN–IgAN patients progressed to end-stage kidney disease (ESKD), including 5 who subsequently died. Serum creatinine at diagnosis was a poor predictor of renal survival. The proportion of patients reaching ESKD or died was higher in FGN–IgAN than in IgAN. The median Kaplan–Meier ESKD-free survival time was 44 months for FGN–IgAN, which was shorter than IgAN (unable to compute, P = 0.013) and FGN (107 months, P = 0.048).

Conclusions

FGN–IgAN is very rare, with clinical presentation and demographics closer to FGN than IgAN. Prognosis is guarded with a median renal survival of 3.6 years. The diagnosis of this dual glomerulopathy requires careful evaluation of immunofluorescence findings, and electron microscopy or DNAJB9 immunohistochemistry.

Immunoglobulin-Negative DNAJB9-Associated Fibrillary Glomerulonephritis: A Report of 9 Cases

Fibrillary glomerulonephritis (FGN) was previously defined by glomerular deposition of haphazardly oriented fibrils that stain with antisera to immunoglobulins but do not stain with Congo red. We report what is to our knowledge the first series of immunoglobulin-negative FGN, consisting of 9 adults (7 women and 2 men) with a mean age at diagnosis of 66 years. Patients presented with proteinuria (100%; mean protein excretion, 3g/d), hematuria (100%), and elevated serum creatinine level (100%). Comorbid conditions included carcinoma in 3 and hepatitis C virus infection in 2; no patient had hypocomplementemia or monoclonal gammopathy. Histologically, glomeruli were positive for DNAJB9, showed mostly mild mesangial hypercellularity and/or sclerosis, and were negative for immunoglobulins by immunofluorescence on frozen and paraffin tissue. Ultrastructurally, randomly oriented fibrils measuring 13 to 20nm in diameter were seen intermingling with mesangial matrix in all and infiltrating glomerular basement membranes in 5. On follow-up (mean duration, 21 months), 2 had disease remission, 4 had persistently elevated serum creatinine levels and proteinuria, and 3 required kidney replacement therapy. Thus, rare cases of FGN are not associated with glomerular immunoglobulin deposition, and the diagnosis of FGN in these cases can be confirmed by DNAJB9 immunostaining. Pathogenesis remains to be elucidated.

Fibrillary glomerulonephritis presenting as crescentic glomerulonephritis in a young female: a case study

Fibrillary glomerulonephritis (FGN) is a rare disorder accounting for up to 1% of all glomerulonephritis (GN). FGN usually manifests as nephrotic or subnephrotic proteinuria, hematuria, and hypertension in patients after the sixth decade. The overall prognosis of FGN is very poor. Crescentic presentation of FGN is uncommon which may be diagnosed as rapidly progressive glomerulonephritis (RPGN) unless electron microscopy and/or special stains are done. We report a case of a young female who presented as RPGN but diagnosis was revised to crescentic FGN after electron microscopy and immunohistochemical staining with DNAJB9 stain. Patient remained dialysis-dependent after treatment with steroid and cyclophosphamide for 2 months and progressed to end-stage renal disease (ESRD). Crescentic FGN usually does not respond to treatment and invariably progresses to ESRD over few months. This case emphasizes the defining role of electron microscopy and special stains in diagnosing uncommon glomerular diseases.

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.

Management and treatment of glomerular diseases (part 2): conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

In November 2017, the Kidney Disease: Improving Global Outcomes (KDIGO) initiative brought a diverse panel of experts in glomerular diseases together to discuss the 2012 KDIGO glomerulonephritis guideline in the context of new developments and insights that had occurred over the years since its publication. During this KDIGO Controversies Conference on Glomerular Diseases, the group examined data on disease pathogenesis, biomarkers, and treatments to identify areas of consensus and areas of controversy. This report summarizes the discussions on primary podocytopathies, lupus nephritis, anti-neutrophil cytoplasmic antibody-associated nephritis, complement-mediated kidney diseases, and monoclonal gammopathies of renal significance.

Fibrillary Glomerulonephritis: Clinicopathologic Features and Atypical Cases from a Multi-Institutional Cohort

BACKGROUND AND OBJECTIVES

Fibrillary GN has been defined as an immune complex-mediated GN with amyloid-like fibrils larger than amyloid which are IgG positive and Congo red negative. With discovery of DNAJB9 as a highly sensitive and specific marker for fibrillary GN, the specificity of the morphologic criteria for establishing the diagnosis of fibrillary GN has come into question.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We sought to (1) determine anatomic characteristics that best define fibrillary GN and (2) identify clinical and pathologic features that predict outcomes.

RESULTS

We retrospectively reviewed kidney biopsies from patients diagnosed with fibrillary GN or suspected fibrillary GN between 1997 and 2017 (n=266, 65% female, median age 61). Approximately 11% of kidney biopsies had one or more unusual feature including monotypic deposits, Congo red positivity, or unusual fibril diameter. Fibrillary GN as a possible monoclonal gammopathy of renal significance represented <1% of cases. Immunostaining for DNAJB9 confirmed fibrillary GN in 100% of cases diagnosed as fibrillary GN and 79% of atypical cases diagnosed as possible fibrillary GN. At a median time of 24 months (interquartile range, 8-46 months) after biopsy (n=100), 53% of patients reached the combined primary outcome of ESKD or death, 18% had CKD, and 18% had partial remission. On multivariable analysis, male sex (adjusted hazard ratio [aHR], 3.82; 95% confidence interval [95% CI], 1.97 to 7.37) and eGFR were the most significant predictors of primary outcome (aHR of 8.02 if eGFR <30 ml/min per 1.73 m2 [95% CI, 1.85 to 34.75]; aHR of 6.44 if eGFR 30 to <45 ml/min per 1.73 m2 [95% CI, 1.38 to 29.99]). Immunosuppressive therapy with rituximab was significantly associated with stabilization of disease progression.

CONCLUSIONS

Detection of DNAJB9 is a useful diagnostic tool for diagnosing atypical forms of fibrillary GN. The outcomes for fibrillary GN are poor and progression to ESKD is influenced predominantly by the degree of kidney insufficiency at the time of diagnosis and male sex. Rituximab may help preserve kidney function for select patients with fibrillary GN.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_11_04_CJN03870319.mp3.

Fibrillary Glomerulonephritis: An Update

Fibrillary glomerulonephritis (FGN) is a rare proliferative form of glomerular disease characterized by randomly oriented fibrillar deposits with a mean diameter of 20 nm. By immunofluorescence (IF), the deposits stain for IgG, C3, and κ and λ light chains, suggesting that the fibrils may be composed of antigen-antibody immune complexes. A recent major advance in our understanding of the pathogenesis of FGN resulted from the discovery that a major component of the fibrils is DNA-J heat-shock protein family member B9 (DNAJB9), and immunohistochemical staining for DNAJB9 now makes it possible to diagnose FGN in the absence of ultrastructural evaluation. FGN has a poor prognosis, treatment options are currently limited, and transplant recurrence is not uncommon.

New developments in the diagnosis of fibrillary glomerulonephritis

Fibrillary glomerulonephritis is a glomerular disease historically defined by glomerular deposition of Congo red-negative, randomly oriented straight fibrils that lack a hollow center and stain with antisera to immunoglobulins. It was initially considered to be an idiopathic disease, but recent studies highlighted association in some cases with autoimmune disease, malignant neoplasm, or hepatitis C viral infection. Prognosis is poor with nearly half of patients progressing to end-stage renal disease within 4 years. There is currently no effective therapy, aside from kidney transplantation, which is associated with disease recurrence in a third of cases. The diagnosis has been hampered by the lack of biomarkers for the disease and the necessity of electron microscopy for diagnosis, which is not widely available. Recently, through the use of laser microdissection-assisted liquid chromatography-tandem mass spectrometry, a novel biomarker of fibrillary glomerulonephritis, DnaJ homolog subfamily B member 9, has been identified. Immunohistochemical studies confirmed the high sensitivity and specificity of DnaJ homolog subfamily B member 9 for this disease; dual immunofluorescence showed its colocalization with IgG in glomeruli; and immunoelectron microscopy revealed its localization to individual fibrils of fibrillary glomerulonephritis. The identification of this tissue biomarker has already entered clinical practice and undoubtingly will improve the diagnosis of this rare disease, particularly in developing countries where electron microscopy is less available. Future research is needed to determine whether DnaJ homolog subfamily B member 9 is an autoantigen or just an associated protein in fibrillary glomerulonephritis, whether it can serve as a noninvasive biomarker, and whether therapies that target this protein are effective in improving prognosis.

Monoclonal gammopathy of renal significance: clinical manifestation, pathogenic characteristic and treatment

Monoclonal gammopathy of renal significance (MGRS) is a group of renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a dangerous plasmatic/B-cell clone hyperplasia through MIg deposition or dysfunction of complement pathway, with increasing risk of progress to end stage renal disease (ESRD) and the underlying hematologic malignancy. The combination of renal biopsy, complete laboratory examination and bone marrow biopsy is an indispensable diagnostic tool for MGRS to identify accurately and unequivocally the pathogenic monoclonal MIg and provide guidance to treatment. Treatment of MGRS is composed of conventional therapy, chemotherapy, and stem cell transplantation to target the underlying clone and eliminate the noxious MIg on the basis of clinical data of some retrospective studies and a small amount of prospective trial. In addition, it is worthwhile point out assessment of therapeutic effect is significantly relevant for renal and overall prognosis. Thus, by comprehensively analyzing the clinical manifestations and pathogenic characteristic of MGRS, early recognition and prompt treatment can improve the prognosis and prevent post-translation recurrence with multidisciplinary cooperation.

Treatment of fibrillary glomerulonephritis with use of repository corticotropin injections

Fibrillary glomerulonephritis (FGN) is a rare idiopathic condition linked to malignancy, autoimmune disorders, monoclonal gammopathies and hepatitis C virus. It usually has a poor prognosis, resulting in progression to end-stage renal disease within a few years, given the lack of standardized treatment. Repository corticotrophin (RC) injections are approved for use in a variety of nephrotic syndromes, but are not routinely considered for treatment of FGN. We present a case in which a patient with FGN began treatment with RC 3 months after diagnosis. The patient has attained partial remission with complete resolution of nephrotic syndrome and stabilization of renal function.

Rituximab and Fibrillary Glomerulonephritis: Interest of B Cell Reconstitution Monitoring

Fibrillary glomerulonephritis (FGN) is a rare glomerular disease characterized by glomerular deposition of randomly arranged non-amyloid fibrils. FGN has a poor renal prognosis and its optimal treatment is a medical challenge. Rituximab therapy has recently emerged as a promising approach even though its mechanism of action remains hypothetical. We describe the case of a 55-year-old woman with FGN successfully treated by rituximab. During the 36-month follow-up, she had three relapses of FGN, occurring each time in the context of B cell recovery. Investigation of the distribution of B cell subpopulations at the time of the third relapse showed, as previously described for some immunological diseases, an increase in the proportion of switched memory B cells relative to healthy subjects, whereas global memory B cell pool was not yet recovered. This case suggests that B cell reconstitution should be carefully monitored in the management of FGN treated with rituximab.

Recurrent glomerular disease after kidney transplantation

PURPOSE OF REVIEW

With improving short-term kidney transplant outcomes, recurrent glomerular disease is being increasingly recognized as an important cause of chronic allograft failure. Further understanding of the risks and pathogenesis of recurrent glomerular disease enable informed transplant decisions, along with the development of preventive and treatment strategies.

RECENT FINDINGS

Multiple observational studies have highlighted differences in rates and outcomes for various recurrent glomerular diseases, although these rates have not markedly improved over the last decade. Emerging evidence supports use of rituximab to treat recurrent primary membranous nephropathy and possibly focal segmental glomerulosclerosis (FSGS), whereas eculizumab is effective in glomerular diseases associated with complement dysregulation [C3 glomerulopathy (C3G) and atypical hemolytic uremic syndrome (aHUS)].

SUMMARY

Despite the potential for recurrence in the allograft, transplant remains the optimal therapy for patients with advanced chronic kidney disease (CKD) secondary to primary glomerular disease. Biomarkers and therapeutic options necessitate accurate pretransplant diagnoses with opportunities for improved surveillance and treatment of recurrent glomerular disease posttransplant.

DnaJ Homolog Subfamily B Member 9 Is a Putative Autoantigen in Fibrillary GN

Fibrillary GN is a rare form of GN of uncertain pathogenesis that is characterized by the glomerular accumulation of randomly arranged, nonbranching fibrils (12-24 nm) composed of Ig and complement proteins. In this study, we used mass spectrometry to comprehensively define the glomerular proteome in fibrillary GN compared with that in controls and nonfibrillary GN renal diseases. We isolated glomeruli from formalin-fixed and paraffin-embedded biopsy specimens using laser capture microdissection and analyzed them with liquid chromatography and data-dependent tandem mass spectrometry. These studies identified DnaJ homolog subfamily B member 9 (DNAJB9) as a highly sampled protein detected only in fibrillary GN cases. The glomerular proteome of fibrillary GN cases also contained IgG1 as the dominant Ig and proteins of the classic complement pathway. In fibrillary GN specimens only, immunofluorescence and immunohistochemistry with an anti-DNAJB9 antibody showed strong and specific staining of the glomerular tufts in a distribution that mimicked that of the immune deposits. Our results identify DNAJB9 as a putative autoantigen in fibrillary GN and suggest IgG1 and classic complement effector pathways as likely mediators of the destructive glomerular injury in this disease.

DnaJ Heat Shock Protein Family B Member 9 Is a Novel Biomarker for Fibrillary GN

Fibrillary GN (FGN) is a rare primary glomerular disease. Histologic and histochemical features of FGN overlap with those of other glomerular diseases, and no unique histologic biomarkers for diagnosing FGN have been identified. We analyzed the proteomic content of glomeruli in patient biopsy specimens and detected DnaJ heat shock protein family (Hsp40) member B9 (DNAJB9) as the fourth most abundant protein in FGN glomeruli. Compared with amyloidosis glomeruli, FGN glomeruli exhibited a >6-fold overexpression of DNAJB9 protein. Sanger sequencing and protein sequence coverage maps showed that the DNAJB9 protein deposited in FGN glomeruli did not have any major sequence or structural alterations. Notably, we detected DNAJB9 in all patients with FGN but not in healthy glomeruli or in 19 types of non-FGN glomerular diseases. We also observed the codeposition of DNAJB9 and Ig-γ Overall, these findings indicate that DNAJB9 is an FGN marker with 100% sensitivity and 100% specificity. The magnitude and specificity of DNAJB9 overabundance in FGN also suggests that this protein has a role in FGN pathogenesis. With this evidence, we propose that DNAJB9 is a strong biomarker for rapid diagnosis of FGN in renal biopsy specimens.

Histologic regression of fibrillary glomerulonephritis: the first report of biopsy-proven spontaneous resolution of disease

Fibrillary glomerulonephritis (FGN) is a rare immune complex type glomerulonephritis characterized by glomerular deposition of randomly oriented fibrils measuring 10–30 nm in thickness, and typically presents with proteinuria with or without renal insufficiency and hematuria. We present a case in which a patient initially presented at age 41 years with nephrotic-range proteinuria and hypertension; a kidney biopsy showed FGN. The patient was treated with angiotensin receptor blockage only, without immunosuppression as per patient preference, and the level of protein in the urine improved. During the follow-up period of 17 years, the patient developed type 2 diabetes mellitus. The patient re-presented with nephrotic-range proteinuria 17 years later, at the age of 58 years. A kidney biopsy was performed and showed diffuse diabetic glomerulosclerosis with secondary focal segmental glomerulosclerosis and related vascular changes. There was no evidence of FGN by immunofluorescence or electron microscopy. Although FGN has been rarely reported to regress clinically, this is the first documented case of histologic regression of FGN. The potential for FGN fibrils to regress spontaneously is important in the management of FGN patients considering that currently available immunosuppressive agents have limited efficacy, and is an encouraging finding for future studies aiming to find a cure for the disease.

A Case of Fibrillary Glomerulonephritis with Fibril Deposition in the Arteriolar Wall and a Family History of Renal Disease

Herein, we report a case of fibrillary glomerulonephritis (FGN). FGN usually shows non-amyloidal fibrils in the mesangium and glomerular capillary walls on electron microscopy. Inherited cases of FGN have been reported in only 3 families, and the suspected genetic form was autosomal dominant. In the present case, the deposition of microfibrils in the arteriolar wall as well as the glomerulus is unique. Our patient's father died of nephrotic syndrome, and his elder brother had a biopsy-proven glomerulopathy. The histological findings of the brothers are similar to mesangial proliferative glomerulonephritis and resemble each other. Therefore, our case is presumed to be familial FGN. Additionally, herein, we review the literature and reconsider the histological and clinical characters of FGN.

Clinical Features and Outcomes of a Racially Diverse Population with Fibrillary Glomerulonephritis

BACKGROUND

Fibrillary glomerulonephritis is characterized by randomly arranged fibrils, approximately 20 nm in diameter by electron microscopy. Patients present with proteinuria, hematuria and kidney insufficiency, and about half of the reported patients progress to end-stage kidney disease within 4 years. The dependence of patient characteristics and outcomes on race has not been explored. In this study, we describe a cohort of patients with fibrillary glomerulonephritis and compare their clinical characteristics and outcomes with those of patients previously described.

METHODS

The University of North Carolina (UNC) Nephropathology Database was used to retrospectively identify patients diagnosed with fibrillary glomerulonephritis between 1985 and 2015. Of these patients, those treated at UNC were selected. Their demographic and clinical characteristics - including signs and symptoms, comorbidities, laboratory values, treatments and outcomes - were compared with those of patients described earlier.

RESULTS

Among the 287 patients identified, 42 were treated at the UNC Kidney Center. When compared to earlier cohorts, a higher frequency of black race, hepatitis C virus (HCV) infection and use of hemodialysis were noted in both black and HCV-positive patients. Autoimmune diseases, infections and malignancies were frequently observed, present in over half of all cases.

CONCLUSION

According to this study, fibrillary glomerulonephritis represents a secondary glomerular disease process (associated with autoimmune disease, infection or malignancy) in many cases and hence screening is essential. As the screening for comorbidities increased over time, more underlying causes were identified. We noted a high frequency of HCV among black patients, suggesting a possible causative association. Treatment of underlying disease is essential for patients for the best outcome.

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.

Paraprotein-Related Kidney Disease: Glomerular Diseases Associated with Paraproteinemias

Paraproteins are monoclonal Igs that accumulate in blood as a result of abnormal excess production. These circulating proteins cause a diversity of kidney disorders that are increasingly being comanaged by nephrologists. In this review, we discuss paraprotein-related diseases that affect the glomerulus. We provide a broad overview of diseases characterized by nonorganized deposits, such as monoclonal Ig deposition disease (MIDD), proliferative GN with monoclonal Ig deposits (PGNMID), and C3 glomerulopathy, as well as those characterized by organized deposits, such as amyloidosis, immunotactoid glomerulopathy, fibrillary GN, and cryoglobulinemic GN, and rarer disorders, such as monoclonal crystalline glomerulopathies, paraprotein-related thrombotic microangiopathies, and membranous-like glomerulopathy with masked IgGκ deposits. This review will provide the nephrologist with an up to date understanding of these entities and highlight the areas of deficit in evidence and future lines of research.