Long-term kidney disease outcomes in fibrillary glomerulonephritis: a case series of 27 patients

Idiopathic fibrillary glomerulonephritis in pediatric patients: addressing treatment challenges in a 12-year-old girl

A 12-year-old girl presented with proteinuria and peripheral edema. Initial evaluation did not identify a clear underlying etiology. Upon the diagnosis of nephrotic syndrome, corticosteroid therapy was initiated. However, the therapeutic response was suboptimal, with persistent proteinuria, the onset of de novo microhematuria, and progressive kidney dysfunction. A kidney biopsy was performed, which led to the diagnosis of fibrillary glomerulopathy, a rare pediatric condition characterized histologically by the presence of fibrillary deposits and positive immunostaining for DNAJB9. There is no established effective treatment for this condition. In our case, the patient was treated with antiproteinuric and calcineurin inhibitors, resulting in complete resolution of microhematuria, normalization of kidney function, and substantial improvement in proteinuria.

Fibrillary Glomerulonephritis and Multiple Myeloma: A Case Report and Literature Review

Introduction

Fibrillary glomerulonephritis (FGN) is a rare form of immune complex-mediated primary glomerular disease frequently coexisting with malignancies or autoimmune diseases. The kidney prognosis is extremely poor, with approximately 50% of patients progressing to end-stage kidney disease within 2-4 years after diagnosis. However, no established treatment currently exists.

Case Presentation

Here we describe a rare case of FGN diagnosed in a patient progressing from monoclonal gammopathy to multiple myeloma. The histopathological findings of the kidney biopsy were consistent with classical FGN and revealed no evidence of myeloma cast nephropathy. Albumin-dominant, Bence Jones protein-negative proteinuria further supported this diagnosis. The patient was successfully treated with anti-myeloma chemotherapies including autologous stem cell transplant, resulting in significant improvement in kidney function.

Conclusion

Based on our experience, secondary FGN associated with plasma cell neoplasms may represent a rare entity that responds favorably to anti-myeloma therapies. Initial investigations to rule out coexistent plasma cell neoplasms are crucial for the optimal management of FGN patients.

[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.

An Updated Comprehensive Review on Diseases Associated with Nephrotic Syndromes

There have been exciting advances in our knowledge of primary glomerular diseases and nephrotic syndromes in recent years. Beyond the histological pattern from renal biopsy, more precise phenotyping of the diseases and the use of modern nephrogenetics helps to improve treatment decisions and sometimes also avoid unnecessary exposure to potentially toxic immunosuppression. New biomarkers have led to easier and more accurate diagnoses and more targeted therapeutic decisions. The treatment landscape is becoming wider with a pipeline of promising new therapeutic agents with more sophisticated approaches. This review focuses on all aspects of entities that are associated with nephrotic syndromes with updated information on recent advances in each field. This includes podocytopathies (focal segmental glomerulosclerosis and minimal-change disease), membranous nephropathy, membranoproliferative glomerulonephritis, IgA nephropathy, fibrillary glomerulonephritis, amyloidosis, and monoclonal gammopathy of renal significance in the context of the nephrotic syndrome, but also renal involvement in systemic diseases, diabetic nephropathy, and drugs that are associated with nephrotic syndromes.

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.

A Case Report of Fibrillary Glomerulonephritis with Mild Albuminuria: A Viewpoint on Proteomics

Fibrillary glomerulonephritis (FGN) is a rare glomerular disorder characterized by the deposition of randomly arranged fibrils in the mesangium and the glomerular basement membrane. Clinical features include massive albuminuria, hematuria, high blood pressure, and kidney failure. Usually, the renal prognosis is not favorable, with evolution to end-stage renal disease in approximately 50% of cases. Recent studies in proteomics have identified a member of the heat shock protein family, also called DNAJB9, which is deposited in the glomerulus of patients with FGN and is not present in other diseases, such as amyloidosis or immunotactoid glomerulopathy. These findings are the first step to clarify the pathogenesis of this disease and could facilitate its diagnosis. Hence, we present a case of FGN with mild albuminuria at baseline and discuss the usefulness of this novel biomarker for diagnosing this group of patients.

Monoclonal gammopathy of renal significance: Multidisciplinary approach to diagnosis and treatment

Monoclonal gammopathy of renal significance (MGRS) is a hemato-nephrological term referring to a heterogeneous group of kidney disorders characterized by direct or indirect kidney injury caused by a monoclonal immunoglobulin (MIg) produced by a B cell or plasma cell clone that does not meet current hematologic criteria for therapy. MGRS-associated kidney diseases are diverse and can result in the development of end stage kidney disease (ESKD). The diagnosis is typically made by nephrologists through a kidney biopsy. Many distinct pathologies have been identified and they are classified based on the site or composition of the deposited Mig, or according to histological and ultrastructural findings. Therapy is directed towards the identified underlying clonal population and treatment decisions should be coordinated between hematologists and nephrologists in a multidisciplinary fashion, depend on the type of MGRS, the degree of kidney function impairment and the risk of progression to ESKD.

IgA-dominant glomerulonephritis with DNAJB9-negative fibrillar polytypic immunoglobulin deposits in the subepithelium

Fibrillary glomerulonephritis (FGN), a rare disease is pathologically characterized by glomerular fibril accumulation ranging from 12 to 24 nm in diameter with negative Congo red staining. Recently, the identification of DnaJ homolog subfamily B member 9 (DNAJB9) as a highly sensitive and specific marker for FGN has revolutionized diagnosis of this disease. However, few recent studies have reported DNAJB9-negative glomerulonephritis with fibrillar deposits. As such, it remains unclear whether DNAJB9-negative cases can be considered equivalent to FGN. Here, we report the case of a 70-year-old woman who developed renal impairment and nephrotic-range proteinuria. Renal biopsy and pathological examination revealed focal glomerulonephritis with fibrocellular crescents. Immunofluorescence microscopy showed IgA-dominant deposition of polytypic IgG in the glomerulus. Electron microscopy revealed hump-like subepithelial electron dense deposits with fibrils of 15-25 nm in diameter. These findings were consistent with FGN; thus, Congo red and direct fast scarlet (DFS) staining, and immunohistochemistry for DNAJB9 were performed. In addition to negative Congo red/DFS/DNAJB9 staining, laser microdissection (LMD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) resulted negative for DNAJB9, which is a highly sensitive and specific marker for FGN. The patient's renal function further declined, prompting administration of rituximab weekly for 2 weeks, similar to the treatment for FGN. This is a unique case of IgA-dominant glomerulonephritis with DNAJB9-negative fibrillar polytypic immunoglobulin deposits in the subepithelium, unlike previous DNAJB9-negative cases. Thus, DNAJB9-negative cases diagnosed based on accurate electron microscopic evaluation must be gathered, and LMD and LC-MS/MS must be used to analyze the organized fibrillar deposits to reveal the disease entity.

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.

Fibrillary Glomerulonephritis and Monoclonal Gammopathy: Potential Diagnostic Challenges

Fibrillary glomerulonephritis (FGN) is a rare glomerular disease featured by the randomly arranged 12- to 24-nm fibrils under electron microscopy (EM). Up to 10% of FGN patients have monoclonal gammopathy. However, distinguishing between FGN as monoclonal gammopathy of renal significance (MGRS) and FGN from other causes with incidental monoclonal gammopathy of undetermined significance (MGUS) can be challenging, as the current way of demonstrating monoclonality is flawed due to (1) the suboptimal sensitivity of kappa staining by immunofluorescence in frozen tissue (IF-F) as compared to pronase-digested paraffin sections (IF-P), causing incorrect labeling of light chain restriction; (2) the unavailability of immunoglobulin G (IgG) subtyping in some centers; and (3) the unavailability of tests demonstrating the monoclonality of highly variable VH or VL domains in immunoglobulin structures in clinical use. The discovery of DnaJ homolog subfamily B member 9 (DNAJB9) allows diagnosis for FGN with less reliance on EM, and the summary of recent studies revealed that genuine MGRS is extremely rare among FGN. Further research integrating IF-P, IgG subtyping, VH or VL domain monoclonality confirmation, and DNAJB9 as diagnostic modalities, with corresponding clinical data including treatment response and prognosis, is required for a better understanding of this subject.

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.

Complete remission of DnaJ homolog subfamily B member 9-positive fibrillary glomerulonephritis following steroid monotherapy in an elderly Japanese woman

A 74-year-old Japanese woman was referred to our department because of anasarca and massive proteinuria. She was clinically diagnosed with nephrotic syndrome, and renal biopsy showed membranoproliferative glomerulonephritis accompanied by marked glomerular infiltration with macrophages and full-house immunofluorescence glomerular deposition. Furthermore, randomly arranged nonbranching fibrils, approximately 12 nm in diameter, were found by electron microscopy, and immunostaining for DnaJ homolog subfamily B member 9 (DNAJB9), a recently identified diagnostic biomarker of fibrillary glomerulonephritis (FGN), showed positive result, thereby confirming the diagnosis of FGN. Steroid treatment was initiated, and she obtained complete remission of nephrotic syndrome and has maintained it. FGN is an uncommon form of glomerular disease, and reported cases of DNAJB9-positive FGN among Asians, particularly among Japanese population, are rare. There have been no established therapeutic regimens and its renal prognosis is generally unfavorable. The present case suggests that some patients with FGN can achieve favorable clinical outcomes through steroid monotherapy.

Fibrillary glomerulonephritis or complement 3 glomerulopathy: a rare case of diffuse necrotising crescentic glomerulonephritis with C3-dominant glomerular deposition and positive DNAJB9

Fibrillary glomerulonephritis (FGN) and complement 3 glomerulopathy (C3G) are rare forms of glomerulonephritis with distinct aetiologies. Both FGN and C3G can present with nephritic syndrome. FGN is associated with autoimmune disease, dysproteinaemia, malignancy and hepatitis C infection. C3G is caused by the unregulated activation of the alternative complement pathway. We present a rare case of diffuse necrotising crescentic glomerulonephritis with dominant C3 glomerular staining on immunofluorescence-consistent with C3G-but electron microscopy (EM) findings of randomly oriented fibrils with a mean diameter of 14 nm and positive immunohistochemistry for DNAJB9-suggestive of FGN. To the best of our knowledge, this is the first reported case of FGN to show dominant C3 glomerular deposits. This case report reaffirms the utility of EM in the evaluation of nephritic syndrome and highlights the value of DNAJB9-a novel biomarker with a sensitivity and specificity near 100% for FGN.

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.

Results of a nation-wide cohort study suggest favorable long-term outcomes of clone-targeted chemotherapy in immunotactoid glomerulopathy

Immunotactoid glomerulopathy is a rare disease defined by glomerular microtubular immunoglobulin deposits. Since management and long-term outcomes remain poorly described, we retrospectively analyzed results of 27 adults from 21 departments of nephrology in France accrued over 19 years. Inclusion criteria were presence of glomerular Congo red-negative monotypic immunoglobulin deposits with ultrastructural microtubular organization, without evidence for cryoglobulinemic glomerulonephritis. Baseline manifestations of this cohort included: proteinuria (median 6.0 g/day), nephrotic syndrome (70%), microscopic hematuria (74%) and hypertension (56%) with a median serum creatinine of 1.5 mg/dL. Nineteen patients had detectable serum and/or urine monoclonal gammopathy. A bone marrow and/or peripheral blood clonal disorder was identified in 18 cases (16 lymphocytic and 2 plasmacytic disorders). Hematologic diagnosis was chronic/small lymphocytic lymphoma in 13, and monoclonal gammopathy of renal significance in 14 cases. Kidney biopsy showed atypical membranous in 16 or membranoproliferative glomerulonephritis in 11 cases, with microtubular monotypic IgG deposits (kappa in 17 of 27 cases), most commonly IgG1. Identical intracytoplasmic microtubules were observed in clonal lymphocytes from 5 of 10 tested patients. Among 21 patients who received alkylating agents, rituximab-based or bortezomib-based chemotherapy, 18 achieved a kidney response. After a median follow-up of 40 months, 16 patients had sustained kidney response, 7 had reached end-stage kidney disease, and 6 died. Chronic/small lymphocytic lymphoma appears as a common underlying condition in immunotactoid glomerulopathy, but clonal detection remains inconstant with routine techniques in patients with monoclonal gammopathy of renal significance. Thus, early diagnosis and hematological response after clone-targeted chemotherapy was associated with favorable outcomes. Hence, thorough pathologic and hematologic workup is key to the management of immunotactoid glomerulopathy.

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.

Successful treatment of a unique case of congophilic fibrillary glomerulonephritis: A case report

INTRODUCTION

Amyloidosis and fibrillary glomerulonephritis (FGN) share similar electron microscopic signatures including random arrangement of fibrils. However, distinction between the 2 can often be made using Congo Red staining.

PATIENT CONCERNS

Here we describe a unique case of FGN, which stained positive for Congo Red, as well as DnaJ heat shock protein family (Hsp40) member B9 which is more specific for FGN. The patient presented with acute kidney injury and severe proteinuria.

DIAGNOSIS

Congophilic FGN.

INTERVENTIONS

Six-month course of mycophenolate mofetil and prednisone.

OUTCOMES

complete resolution of acute kidney injury and proteinuria TAKE HOME LESSONS:: To our knowledge, this is the first reported case of successful treatment of this rare condition using mycophenolate mofetil and prednisone.

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.

IgM monoclonal gammopathy with heavy-and-light-chain amyloidosis resembling fibrillary glomerulonephritis determined by tandem mass spectrometry: a case report

BACKGROUND

Fibrillary glomerulonephritis (FGN) is distinguished from amyloidosis by thicker fibrils and the lack of staining with histochemical dyes typically reactive with amyloid. However, congophilic FGN has been proposed recently and adding laser microdissection followed by mass spectrometry (LMD/MS) to conventional pathological methods would be helpful to diagnose FGN. Here, we report a patient initially diagnosed with FGN whose final pathological diagnosis was changed to immunoglobulin heavy-and-light-chain amyloidosis (AHL) after LMD/MS.

CASE PRESENTATION

A 75-year-old male developed nephrotic syndrome. Protein electrophoresis showed IgM κ type M proteinemia and he was diagnosed with IgM monoclonal gammopathy. A renal biopsy was performed and pathological examination showed marked periodic acid-Schiff-positive enlargement of the mesangial region and silver stain positivity, but weak direct fast scarlet staining. Immunofluorescence analysis showed monoclonal deposition of IgM-κ chain in the glomerulus. Under electron microscopy, the fibrils were about 20 nm in diameter, which was thicker than typical amyloid fibrils. Based on these findings, the patient was diagnosed with FGN. Although cyclophosphamide and prednisolone were administered, his renal function deteriorated and progressed to end stage renal disease requiring maintenance hemodialysis. As congophilic FGN has been recognized since 2018, Congo red staining and LMD/MS were performed. The Congo red staining was positive and LMD/MS results indicated that this was a case of AHL.

CONCLUSIONS

We reported a case of μ and κ chain AHL resembling FGN requiring LMD/MS for definitive diagnosis. Since FGN and amyloidosis exhibit pathological findings, even if Congo red staining is positive, LMD/MS needs to be considered in cases atypical pathological findings, such as silver stain positivity or thicker fibrils.

DNAJB9-positive monotypic fibrillary glomerulonephritis is not associated with monoclonal gammopathy in the vast majority of patients

The association of fibrillary glomerulonephritis (FGN) with monoclonal gammopathy has been controversial, although monotypic FGN is currently classified as a monoclonal gammopathy of renal significance (MGRS) lesion. To define this lesion, we correlated findings by immunofluorescence on frozen and paraffin tissue, IgG subtype staining and serum protein electrophoresis with immunofixation in patients with monotypic FGN. Immunofluorescence was performed on paraffin sections from 35 cases of DNAJB9-associated FGN that showed apparent light chain restriction of glomerular IgG deposits by standard immunofluorescence on frozen tissue. On paraffin immunofluorescence, 15 cases (14 lambda and one kappa restricted cases on frozen tissue immunofluorescence) showed no light chain restriction, 19 showed similar light chain restriction, and one was negative for both light chains. Seven of the 15 cases with masked polyclonal deposits also had IgG subclass restriction and these cases would have been diagnosed as a form of monoclonal protein-associated glomerulonephritis if paraffin immunofluorescence was not performed. Monotypic FGN (confirmed by paraffin immunofluorescence and IgG subclass restriction) accounted for only one of 151 (0.7%) patients with FGN encountered during the last two years. Only one of 11 of cases had a detectable circulating monoclonal protein on serum protein electrophoresis with immunofixation. We propose that paraffin immunofluorescence is required to make the diagnosis of lambda-restricted monotypic FGN as it unmasked polytypic deposits in over half of patients. When confirmed by paraffin immunofluorescence and IgG subclass staining, DNAJB9-positive monotypic FGN is very rare and is not associated with monoclonal gammopathy in the vast majority of patients. Thus, there is a question whether this lesion should be included in MGRS-related diseases.

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.

The evaluation of monoclonal gammopathy of renal significance: a consensus report of the International Kidney and Monoclonal Gammopathy Research Group

The term monoclonal gammopathy of renal significance (MGRS) was introduced by the International Kidney and Monoclonal Gammopathy Research Group (IKMG) in 2012. The IKMG met in April 2017 to refine the definition of MGRS and to update the diagnostic criteria for MGRS-related diseases. Accordingly, in this Expert Consensus Document, the IKMG redefines MGRS as a clonal proliferative disorder that produces a nephrotoxic monoclonal immunoglobulin and does not meet previously defined haematological criteria for treatment of a specific malignancy. The diagnosis of MGRS-related disease is established by kidney biopsy and immunofluorescence studies to identify the monotypic immunoglobulin deposits (although these deposits are minimal in patients with either C3 glomerulopathy or thrombotic microangiopathy). Accordingly, the IKMG recommends a kidney biopsy in patients suspected of having MGRS to maximize the chance of correct diagnosis. Serum and urine protein electrophoresis and immunofixation, as well as analyses of serum free light chains, should also be performed to identify the monoclonal immunoglobulin, which helps to establish the diagnosis of MGRS and might also be useful for assessing responses to treatment. Finally, bone marrow aspiration and biopsy should be conducted to identify the lymphoproliferative clone. Flow cytometry can be helpful in identifying small clones. Additional genetic tests and fluorescent in situ hybridization studies are helpful for clonal identification and for generating treatment recommendations. Treatment of MGRS was not addressed at the 2017 IKMG meeting; consequently, this Expert Consensus Document does not include any recommendations for the treatment of patients with MGRS.

This Expert Consensus Document from the International Kidney and Monoclonal Gammopathy Research Group includes an updated definition of monoclonal gammopathy of renal significance (MGRS) and recommendations for the use of kidney biopsy and other modalities for evaluating suspected MGRS

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.

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.

The association of hepatitis C infection with the onset of CKD and progression into ESRD

Hepatitis C virus (HCV) infection is not only an important cause of chronic liver disease, but extrahepatic manifestations are common and include chronic kidney disease (CKD). HCV is classically associated with cryoglobulinemic glomerulonephritis in the context of mixed cryoglobulinemia syndrome, but other glomerular diseases also occur and may be significantly under-recognized. HCV may cause glomerular disease by immune complex deposition; however, other potential mechanisms by which HCV promotes CKD include a direct cytopathic effect of the virus on renal tissue, and by its association with accelerated atherosclerosis, insulin resistance, and chronic inflammation. Epidemiologic studies show HCV infection confers an increased risk of incident CKD and accelerates progression of CKD to end-stage renal disease (ESRD) in the general population, as well as subpopulations including diabetic patients, those coinfected with human immunodeficiency virus (HIV), and kidney transplant recipients. Patients with CKD and HCV infection experience inferior clinical outcomes, including poorer quality of life and an increased risk of mortality. Treatment with interferon-based regimens is associated with decreased risk of incident CKD and ESRD, though prior studies are limited by the small number of patients with HCV and CKD who underwent treatment. With the advent of new, well-tolerated direct-acting antiviral combinations that are not cleared by the kidneys, it is possible to treat all genotypes of HCV infection in patients with CKD and ESRD. More data on the effect of direct-acting antivirals on CKD incidence and progression are necessary. However, there is every expectation that with improved access to HCV treatment, the burden of CKD in patients with HCV could significantly decline.

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.

Fibrillary Glomerulonephritis with Crescentic and Necrotizing Glomerulonephritis and Concurrent Thrombotic Microangiopathy

We present a 77-year-old Caucasian woman who presented with nephrotic-range proteinuria, microhematuria, renal impairment, and extremely elevated blood pressure. She had a long history of well-controlled type 2 diabetes. Renal biopsy revealed fibrillary deposits in the mesangium and glomerular basement membrane consistent with fibrillary glomerulopathy (FGN), with crescentic changes and thrombotic microangiopathy (TMA). We could not identify any radiological, clinical, or laboratory evidence of autoimmune disorders, lymphoproliferative disorders, and malignancy. It was decided not to offer her any immunosuppressive therapy, as she was frail with substantial renal damage on the biopsy. Five months after presentation, she gradually progressed to requiring renal replacement therapy and is currently on maintenance hemodialysis. Crescentic changes in FGN, though rare, have been previously described, but the concurrent presence of TMA has never been previously reported.

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.

Dysproteinemias and Glomerular Disease

Dysproteinemia is characterized by the overproduction of an Ig by clonal expansion of cells from the B cell lineage. The resultant monoclonal protein can be composed of the entire Ig or its components. Monoclonal proteins are increasingly recognized as a contributor to kidney disease. They can cause injury in all areas of the kidney, including the glomerular, tubular, and vascular compartments. In the glomerulus, the major mechanism of injury is deposition. Examples of this include Ig amyloidosis, monoclonal Ig deposition disease, immunotactoid glomerulopathy, and cryoglobulinemic GN specifically from types 1 and 2 cryoglobulins. Mechanisms that do not involve Ig deposition include the activation of the complement system, which causes complement deposition in C3 glomerulopathy, and cytokines/growth factors as seen in thrombotic microangiopathy and precipitation, which is involved with cryoglobulinemia. It is important to recognize that nephrotoxic monoclonal proteins can be produced by clones from any of the B cell lineages and that a malignant state is not required for the development of kidney disease. The nephrotoxic clones that do not meet requirement for a malignant condition are now called monoclonal gammopathy of renal significance. Whether it is a malignancy or monoclonal gammopathy of renal significance, preservation of renal function requires substantial reduction of the monoclonal protein. With better understanding of the pathogenesis, clone-directed strategies, such as rituximab against CD20 expressing B cell and bortezomib against plasma cell clones, have been used in the treatment of these diseases. These clone-directed therapies been found to be more effective than immunosuppressive regimens used in nonmonoclonal protein-related kidney diseases.

Proliferative lupus nephritis in the absence of overt systemic lupus erythematosus: A historical study of 12 adult patients

Severe lupus nephritis in the absence of systemic lupus erythematosus (SLE) is a rare condition with an unclear clinical presentation and outcome.We conducted a historical observational study of 12 adult (age >18 years) patients with biopsy-proven severe lupus nephritis or lupus-like nephritis without SLE immunological markers at diagnosis or during follow-up. Excluded were patients with chronic infections with HIV or hepatitis B or C; patients with a bacterial infectious disease; and patients with pure membranous nephropathy. Electron microscopy was retrospectively performed when the material was available. End points were the proportion of patients with a complete response (urine protein to creatinine ratio <0.5 g/day and a normal or near-normal eGFR), partial response (≥50% reduction in proteinuria to subnephrotic levels and a normal or near-normal eGFR), or nonresponse at 12 months or later after the initiation of the treatment.The study included 12 patients (66% female) with a median age of 36.5 years. At diagnosis, median creatinine and proteinuria levels were 1.21 mg/dL (range 0.5-11.6) and 7.5 g/day (1.4-26.7), respectively. Six patients had nephrotic syndrome and acute kidney injury. Renal biopsy examinations revealed class III or class IV A/C lupus nephritis in all cases. Electron microscopy was performed on samples from 5 patients. The results showed mesangial and subendothelial dense deposits consistent with LN in 4 cases, and a retrospective diagnosis of pseudo-amyloid fibrillary glomerulonephritis was made in 1 patient.Patients received immunosuppressive therapy consisting of induction therapy followed by maintenance therapy, similar to treatment for severe lupus nephritis. Remission was recorded in 10 patients at 12 months after the initiation of treatment. One patient reached end-stage renal disease. After a median follow-up of 24 months, 2 patients relapsed.Lupus nephritis in the absence of overt SLE is a nosological entity requiring careful etiological investigation, including systematic electron microscopy examination of renal biopsies to rule out fibrillary glomerulonephritis. In this series, most patients presented with severe glomerulonephritis, which was highly similar to lupus nephritis at presentation and in terms of response to immunosuppressive therapy.

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.

The Scope of Kidney Affection in Monoclonal Gammopathies at All Levels of Clinical Significance

Multiple myeloma (MM) is one of the most important clonal malignant plasma cell disorders and renal involvement is associated with poor prognosis. Although there are several reasons for renal impairment in MM, the main cause is the toxic effects of monoclonal proteins. Although cast nephropathy is the best known and unchallenged diagnosis for hematologists and pathologists, the renal effects of monoclonal gammopathy can be various. Monoclonal gammopathy of renal significance was proposed by the International Kidney and Monoclonal Gammopathy Research Group for renal lesions in monoclonal gammopathy in recent years. Renal lesions in monoclonal gammopathy can be grouped as follows: light chain (cast) nephropathy, acute tubular injury/necrosis, tubulointerstitial nephritis, amyloidosis, monoclonal Ig deposition diseases, immunotactoid glomerulopathy, type I cryoglobulinemia, proliferative glomerulonephritis with monoclonal IgG deposits, C3 glomerulopathy with monoclonal gammopathy, and crystal-storing histiocytosis, considering the previous and new terminology. In this study, renal involvement of monoclonal gammopathies, in terms of previous and new terminology, was reviewed.

[Classification and therapeutic management of monoclonal gammopathies of renal significance]

Two categories of renal disorders associated with monoclonal gammopathies are to be distinguished, according to the characteristics of the underlying B-cell clone. The first group of renal diseases always occurs in the setting of high tumor mass with production of large amounts of monoclonal immunoglobulins. The main complication is the so-called myeloma cast nephropathy, which almost invariably complicates high tumor mass myeloma. The second group includes all renal disorders caused by a monoclonal immunoglobulin secreted by a nonmalignant B-cell clone, and currently referred as a "monoclonal gammopathy of renal significance (MGRS)". This term was introduced to distinguish monoclonal gammopathies that are responsible for the development of kidney damage from those that are truly benign. The spectrum of renal diseases in MGRS is wide and its classification relies on the localization of renal lesions, either glomerular or tubular, and on the pattern of ultrastructural organization of immunoglobulin deposits. Physicochemical characteristics of the pathogenic monoclonal immunoglobulin are probably involved in their propensity to deposit or precipitate in the kidney, as illustrated by the high rate of recurrence of each specific type after kidney transplantation. Early diagnosis and efficient chemotherapy targeting the causal B-cell clone are mandatory to improve renal prognosis and patient survival.

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.