Membranous nephropathy associated with IgG4-related disease

Renal Manifestations of IgG4-Related Disease: A Concise Review

IgG4-related disease (IgG4-RD) is an immune-mediated disorder marked by fibro-inflammatory masses that can infiltrate multiple organ systems. Due to its relatively recent discovery and limited understanding of its pathophysiology, IgG4-related disease may be difficult to recognize and is consequently potentially underdiagnosed. Renal involvement is becoming regarded as one of the key features of this disease. To date, the most well-recognized renal complication of IgG4-related disease is tubulointerstitial nephritis, but membranous glomerulonephritis, renal masses, and retroperitoneal fibrosis have also been reported. This concise review has two objectives. First, it will briefly encapsulate the history, epidemiology, and presentation of IgG4-related disease. Second, it will examine the reported renal manifestations of IgG4-related disease, exploring the relevant histology, imaging, clinical features, and treatment considerations. This synthesis will be highly relevant for nephrologists, rheumatologists, general internists, and renal pathologists to raise awareness and help improve early recognition of IgG4-related kidney disease (IgG4-RKD).

Remission Induction of IgG4-related Membranous Nephropathy with Multitarget Therapy

IgG4-related membranous nephropathy (MN) is often refractory to glucocorticoid (GC) therapy, and treatment remains unclear. We herein report a 67-year-old Japanese man with IgG4-related MN and tubulointerstitial nephritis. A post-gastroscopy antibody test revealed Helicobacter pylori infection. After eradication, his proteinuria decreased indefinitely. We started prednisolone (30 mg/day), long-term GCs, and immunosuppressant therapy. However, remission proved challenging to achieve, with persistent proteinuria present at 1.0-2.0 g/gCr. We performed multitarget therapy for refractory IgG4-related MN, achieving proteinuria remission (<0.3 g/gCr). Multitarget therapy with low-dose GCs can resolve refractory IgG4-related MN through remission induction of proteinuria and minimize the risks associated with GC therapy.

The expanding spectrum and utility of antigens in membranous nephropathy

PURPOSE OF REVIEW

Multiple antigenic targets were discovered in membranous nephropathy, representing distinct autoimmune diseases with a similar morphologic pattern of injury. An overview of recent developments, including antigen types, clinical associations, serologic monitoring, and advancements in understanding disease pathogenesis are provided.

RECENT FINDINGS

Several new antigenic targets have defined subtypes of membranous nephropathy, including Neural epidermal growth factor-like 1, protocadherin 7, HTRA1, FAT1, SEMA3B, NTNG1, NCAM1, exostosin 1/2, transforming growth factor beta receptor 3, CNTN1, proprotein convertase subtilisin/kexin type 6, and neuron-derived neurotrophic factor. Autoantigens in membranous nephropathy may demonstrate unique clinical associations, assisting the nephrologist to identify potential disease etiologies and triggers, such as autoimmune disease, cancer, medications, and infections.

SUMMARY

We are entering an exciting era for which an antigen-based approach will further define subtypes of membranous nephropathy, allow for development of noninvasive diagnostics, and improve care for patients.

Recent advances in IgG4-related kidney disease

Recent advances in the management and understanding of immunoglobulin (Ig)G4-related kidney disease (RKD) have emphasized the importance of urgent treatment in IgG4-related tubulointerstitial nephritis. On the other hand, to avoid long-term glucocorticoid toxicity, strategies for early withdrawal of steroids or combination of immunosuppressants, such as rituximab, and the minimum dose of steroids have been pursued. However, disease recurrence after reducing or stopping steroid therapy hampers early withdrawal of glucocorticoid maintenance therapy. In addition, knowledge has accumulated in diagnostic approaches including differential diagnosis of anti-neutrophil cytoplasmic antibodies-associated vasculitis, idiopathic multicentric Castleman's disease, and Rosai-Dorfman disease with kidney lesion, which leads to earlier and precise diagnosis of IgG4-RKD. This review summarizes recent progress in the differential diagnosis of IgG4-RKD and related treatment strategies and recent topics of hypocomplementaemia, membranous glomerulonephritis, and IgG4-related pyelitis and periureteral lesion.

Membranous nephropathy associated with immunoglobulin G4-related disease successfully treated with obinutuzumab

Immunoglobulin G4 (IgG4)-releated disease is typically associated with interstitial nephritis, but rare cases of idiopathic membranous nephropathy as a renal manifestation have been described. Obinutuzumab was successfully used in refractory membranous nephropathy, but evidence for the treatment of IgG4-related disease with obinutuzumab is lacking. We report one patient's case with membranous nephropathy associated with IgG4-related disease who was treated with obinutuzumab following an anaphylactic reaction to rituximab. Obinutuzumab treatment resulted in a sustained complete remission of membranous nephropathy and a decrease of IgG4 to the normal range. This case demonstrates that membranous nephropathy associated with IgG4-related disease can be treated successfully with obinutuzumab.

A Case of M-Type Phospholipase A2 Receptor-Associated Membranous Nephropathy With IgG4-Positive Cells Infiltration in the Interstitium

A 70-year-old man was referred to our department for evaluation of nephrotic syndrome. Renal biopsy revealed membranous nephropathy (MN). Immunohistochemical analysis demonstrated IgG4-positive staining in the glomeruli and interstitial cells. The presence of serum anti-phospholipase A2 receptor (PLA2R) antibody and enhanced staining of PLA2R in the glomeruli was noted. Computed tomography unidentified the extrarenal lesions of IgG4-related disease. He was diagnosed with PLA2R-associated MN possibly complicated with IgG4 related kidney disease (IgG4-RKD). Storiform fibrosis, a typical manifestation of IgG4-RKD, was not apparent. We herein describe a case of serologically and histologically confirmed PLA2R-associated MN with IgG4+ cell infiltration into the interstitium without any signs of IgG4-RD.

IgG4-related nephritis and interstitial pulmonary disease complicated by invasive pulmonary fungal infection: a case report

Background

IgG4-related kidney disease (IgG4-RKD) can affect multiple organs, which was first reported as a complication or extra-organ manifestation of autoimmune pancreatitis in 2004. It is characterized by abundant IgG4-positive plasma cells infiltration in tissues involved.

Case presentation

A 69-year-old man presented with cough and renal dysfunction with medical history of hypertension and diabetes. Pathological findings revealed interstitial nephritis and he was initially diagnosed with IgG4-RKD. Prednisone helped the patient to get a remission of cough and an obvious decrease of IgG4 level. However, he developed invasive pulmonary fungal infection while steroid theatment. Anti-fungal therapy was initiated after lung puncture (around cavitary lung lesion). Hemodialysis had been conducted because of renal failure and he got rid of it 2 months later. Methylprednisolone was decreased to 8 mg/day for maintenance therapy. Anti-fungal infection continued for 4 months after discharge home. On the 4th month of follow-up, Chest CT revealed no progression of lung lesions.

Conclusions

The corticosteroids are the first-line therapy of IgG4-RD and a rapid response helps to confirm the diagnosis. This case should inspire clinicians to identify IgG4-related lung disease and secondary pulmonary infection, pay attention to the complications during immunosuppressive therapy for primary disease control.

Low-density lipoprotein apheresis for PLA2R-related membranous glomerulonephritis accompanied by IgG4-related tubulointerstitial nephritis

IgG4-related disease preferentially involves the kidney by tubulointerstitial nephritis with IgG4-positive plasma cell filtration and/or membranous glomerulonephritis. We reported the case of a 68-year-old man with IgG4-related tubulointerstitial nephritis combined with antiphospholipase A2 receptor (PLA2R)-related membranous glomerulonephritis, in which distinguishing between idiopathic PLA2R-related and IgG4-related secondary membranous glomerulonephritis was difficult. We diagnosed him as having IgG4-related disease, based on a serum IgG4 level of 170 mg/dL and the presence of IgG4-related parotiditis. On renal biopsy, there was tubulointerstitial nephritis with IgG4-positive plasma cell filtration, which was compatible with IgG4-related disease and membranous glomerulonephritis, with concomitant positive staining for PLA2R on immunofluorescence microscopy. The renal function immediately recovered after steroid treatment, probably because of the improvement in the tubulointerstitial lesions, but his nephrotic syndrome was steroid-resistant. Low-density lipoprotein (LDL) apheresis therapy was effective for membranous glomerulonephritis and increased his serum albumin from 1.4 to 2.8 g/dL. Although IgG4-related kidney disease usually accompanies secondary membranous glomerulonephritis, the positive PLA2R staining suggested a concomitant primary membranous glomerulonephritis. The recent treatment strategy, including LDL apheresis, for primary and secondary membranous glomerulonephritis was discussed briefly in this report.

Renal involvement in IgG4-related disease

IgG4-RD may affect several organs including kidneys. The kidney is involved in approximately 20% of patient with IgG4-RD. The most common intrinsic kidney disease is tubulointerstitial nephritis (IgG4-TIN). Retroperitoneal fibrosis (IgG4-RPF) may induce obstructive acute renal failure. More rarely, IgG4-RKD can manifest as a glomerular disease, in particular as a membranous nephropathy (MN). It mostly affects middle-aged to elderly men and causes acute or chronic renal dysfunction, multiple hypodense lesions on CT-Scan and various extra-renal lesions. Increased serum IgG4 and hypocomplementemia are the most important serological findings for the diagnosis of IgG4-RD and thus should be systematically assessed when IgG4-RKD is suspected. Specific diagnosis criteria for IgG4-TIN including interstitial infiltration of IgG4-positive plasma cells, storiform fibrosis and tubular basement membrane immune complex deposits have been proposed. Corticosteroids are effective and remain the first-line therapy but relapses or severe forms could respond to immunosuppressive therapy.

PLA2R-Negative Membranous Nephropathy Presenting as a Prodrome of IgG4-Related Autoimmune Pancreatitis

Membranous nephropathy (MN) with tubulointerstitial nephritis (TIN) is an established manifestation of immunoglobulin G4 (IgG4)-related disease (IgG4-RD). A pathological feature aiming to distinguish between primary and secondary MN is the presence or absence of glomerular staining for phospholipase A2 receptor (PLA2R), respectively. Isolated MN without TIN has been rarely reported in the context of IgG4-RD. This case report describes a patient with a history of MN successfully treated with steroids and cyclophosphamide, who, 3 years later, presented with unexplained exacerbation of diabetes mellitus due to IgG4-related autoimmune pancreatitis. Pancreatitis was treated, and diabetes improved after treatment with steroids. Based on the presence of isolated IgG4 glomerular capillary deposits along with negative staining for PLA2R and the metachronous appearance of autoimmune pancreatitis, MN was retrospectively classified as secondary to IgG4-RD. Isolated IgG4-positive/PLA2R-negative MN without TIN can be a prodrome of IgG4-RD, reminiscent of MN secondary to neoplasms.

An IgA1-lambda-type monoclonal immunoglobulin deposition disease associated with membranous features in a patient with IgG4-related kidney disease: a case report

BACKGROUND

IgG4-related disease (IgG4-RD) is a newly recognized fibroinflammatory condition. The kidney is one of the organs commonly affected by IgG4-RD. Tubulointerstitial nephritis (TIN) is the main feature, and membranous nephropathy (MN) has also been described frequently. In MN, polyclonal immunoglobulins and complements are deposited in granular form along the glomerular basement membranes (GBMs). Unusual cases of monoclonal immunoglobulin deposition disease (MIDD) associated with membranous features have been reported. MIDD is morphologically similar to MN but contains immunoglobulins considered to be derived from single B-cell clone.

CASE PRESENTATION

We describe a 65-year-old man who was referred to our hospital because of hyperproteinaemia, eosinophilia, anaemia, and proteinuria. A renal biopsy demonstrated infiltration of plasma cells and eosinophils in the interstitium, and the ratio of IgG4-positive plasma cells to IgG-positive plasma cells was 55%. The patient was diagnosed as having IgG4-related TIN. Periodic acid methenamine silver staining under light microscopy revealed a bubbling appearance and spike formation in the GBM. On immunofluorescence, the expression of IgG and complements was negative; however, IgA was positively expressed in a granular pattern along the GBM. An IgA subclass analysis revealed a significant deposition of IgA1-lambda (IgA1-λ). Electron microscopy revealed irregular and small non-organized and non-Randall-type granular electron-dense deposits in the GBM that were shaped like snow leopard spots.

CONCLUSIONS

After corticosteroid therapy was initiated, the patient's eosinophilia remarkably improved and his serum creatinine, IgG, and IgG4 levels decreased to within the normal ranges. However, massive proteinuria persisted. To our knowledge, this is the first reported case of IgG4-related TIN associated with IgA1-λ-type MIDD with membranous features.

A Refractory Case of Secondary Membranous Nephropathy Concurrent with IgG4-related Tubulointerstitial Nephritis

A 58-year-old man with type 1 autoimmune pancreatitis was referred to nephrologists for severe proteinuria. Laboratory data revealed a high serum IgG4 level, hypoalbuminemia, and massive proteinuria, which were compatible with nephrotic syndrome. The renal pathological findings confirmed the diagnosis of secondary membranous nephropathy concurrent with IgG4-related tubulointerstitial nephritis. Despite the improvement of interstitial markers, the proteinuria was refractory to prednisolone, requiring cyclosporine to achieve complete remission. Membranous nephropathy is a rare manifestation of IgG4-related kidney disease. This case shows that the therapeutic response to prednisolone significantly differs between glomerular lesions and interstitial lesions of IgG4-related kidney disease.

The clinicopathological features of patients with membranous nephropathy

Background

Membranous nephropathy (MN) represents a distinct glomerular disease which has been considered as a major cause of nephrotic syndrome (NS) in adults. Evidences show that the clinicopathological features of MN are various among MN cases. This study aimed to summarize and analyze the clinicopathological features of patients with MN.

Methods

A total of 231 MN patients were recruited in this study. Their clinical and pathological features were collected and analyzed according to their age, gender, pathological stages, and anti-phospholipase A2 receptor (anti-PLA2R) antibodies tests.

Results

Among the 231 MN cases, the ratio of male to female was 1.47 and the mean age was 47.43±14.32 years. Altogether, 163 (70.6%) cases were positive for NS. Their serum antiPLA2R, body mass index, total cholesterol, triglyceride, low density lipoprotein cholesterol, D2, IgA, and IgE were increased, but IgG was decreased. The majority of the patients were middle aged and old aged. In addition, the pathological stage was significantly correlated with gender (P=0.038), creatinine, (P=0.021) and IgE (P=0.003). A total of 74.9% MN patients were found to be positive for anti-PLA2R antibodies, and they were more likely to have abnormal serum indices.

Conclusion

The major clinicopathological characteristics of MN patients are summarized in this study. Male and elder MN cases are likely to have rapid disease progression. Advanced pathological stages and being positive for anti-PLA2R antibodies may be potential indicators for disease activity of MN.

Immunoglobulin G4-related kidney disease: Pathogenesis, diagnosis, and treatment

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized clinical entity that often involves multiple organs; it is characterized by high levels of serum immunoglobulin G4 (IgG4), dense infiltration of IgG4+ cells, and storiform fibrosis. Cellular immunity, particularly T cell-mediated immunity, has been implicated in the pathogenesis of IgG4-RD. The most frequent renal manifestations of IgG4-RD are IgG4-related tubulointerstitial nephritis, membranous glomerulonephropathy (MGN), and obstructive nephropathy secondary to urinary tract obstruction due to IgG4-related retroperitoneal fibrosis, prostatitis, or ureter inflammation. Kidney function impairment can be acute or chronic. In IgG4-MGN, proteinuria can be in the nephrotic range. The diagnosis of IgG4-related kidney disease should not be based solely on serum IgG4 levels or the number of tissue-infiltrating IgG4+ plasma cells. Diagnosis should be based on specific histopathological findings, confirmed by tissue immunostaining and an appropriate clinical context. Steroid treatment is the first-line therapy. For relapsing or refractory cases, immunosuppressants could be combined with steroids. In hydronephrosis patients, appropriate immunosuppressive therapy could preclude the implantation of a double J ureteral catheter.

Retrospective Study of Phospholipase A2 Receptor and IgG Subclasses in Glomerular Deposits in Chinese Patients with Membranous Nephropathy

BACKGROUND AND OBJECTIVES

The research work in the past years showed that detection of phospholipase A2 receptor (PLA2R) antigen and its dominant IgG4 autoantibody in glomerular deposits of patients with membranous nephropathy (MN) was useful for the differentiation between primary MN (PMN) and secondary MN (SMN), but so far such research data from large Chinese patient series is little. Here, we are going to report a research work in a Chinese cohort.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study enrolled 179 patients with PMN, 40 patients with membranous lupus nephritis (LN-MN), 26 patients with hepatitis B virus-associated MN (HBV-MN), 2 patients with malignancy-associated MN (M-MN) and one patient with IgG4-related MN (IgG4-MN). PLA2R and IgG subclasses in glomerular deposits of these patients were examined by immunofluorescence and/or immunohistochemical staining, and the potential value of the above examinations for differential diagnosis of PMN and SMN was evaluated.

RESULTS

Glomerular PLA2R deposition was present in 92.2% patients with PMN and 7.7% patients with HBV-MN, but none of the patients with LN-MN. Predominant/codominant IgG4 deposition was found in 93.3% patients with PMN and 11.5% patients with HBV-MN, but none of the patients with LN-MN. The two M-MN patients both had glomerular PLA2R and predominant/codominant IgG4 deposition. The one IgG4-MN patient had deeply staining IgG4 but no PLA2R in glomeruli.

CONCLUSIONS

The glomerular PLA2R and predominant/codominant IgG4 deposition is frequently observed in Chinese patients with PMN. Immunofluorescence and immunohistochemical staining of renal biopsy tissue for detection of glomerular PLA2R and IgG subclasses deposition can help to distinguish PMN from LN-MN and most of HBV-MN.

Idiopathic Retroperitoneal Fibrosis

Idiopathic retroperitoneal fibrosis (RPF), reviewed herein, is a rare fibro-inflammatory disease that develops around the abdominal aorta and the iliac arteries, and spreads into the adjacent retroperitoneum, where it frequently causes ureteral obstruction and renal failure. The clinical phenotype of RPF is complex, because it can be associated with fibro-inflammatory disorders involving other organs, is considered part of the spectrum of IgG4-related disease, and often arises in patients with other autoimmune conditions. Obstructive uropathy is the most common complication, although other types of renal involvement may occur, including stenosis of the renal arteries and veins, renal atrophy, and different types of associated GN. Environmental and genetic factors contribute to disease susceptibility, whereas the immunopathogenesis of RPF is mediated by different immune cell types that eventually promote fibroblast activation. The diagnosis is made on the basis of computed tomography or magnetic resonance imaging, and positron emission tomography is a useful tool in disease staging and follow-up. Treatment of idiopathic RPF aims at relieving ureteral obstruction and inducing disease regression, and includes the use of glucocorticoids, combined or not with other traditional immunosuppressants. However, biologic therapies such as the B cell-depleting agent rituximab are emerging as potentially efficacious agents in difficult-to-treat cases.

Overview of IgG4-Related Tubulointerstitial Nephritis and Its Mimickers

Tubulointerstitial nephritis (TIN) is the most common form of renal involvement in IgG4-related disease. It is characterized by a dominant infiltrate of IgG4-positive plasma cells in the interstitium and storiform fibrosis. Demonstration of IgG4-positive plasma cells is essential for diagnosis, but the number of IgG4-positive cells and the ratio of IgG4-positive/IgG-positive plasma cells may vary from case to case and depending on the methods of tissue sampling even in the same case. IgG4-positive plasma cells can be seen in TIN associated with systemic lupus erythematosus, Sjögren syndrome, or anti-neutrophil cytoplasmic antibody–associated vasculitis, which further add diagnostic confusion and difficulties. To have a more clear view of IgG4-TIN and to delineate differential points from other TIN with IgG4-positive plasma cell infiltrates, clinical and histological features of IgG4-TIN and its mimickers were reviewed. In the rear part, cases suggesting overlap of IgG4-TIN and its mimickers and glomerulonephritis associated with IgG4-TIN were briefly described.

IgG4-related kidney disease--an update

Purpose of review

IgG4-related disease (IgG4-RD) is a recently recognized systemic inflammatory disorder that can affect most organs/tissues such as sarcoidosis. The kidney is a frequently affected organ with tubulointerstitial nephritis (TIN), the representative lesion of IgG4-RD. This review focuses on the latest knowledge of IgG4-related kidney disease (IgG4-RKD).

Recent findings

A wide range of renal manifestations of IgG4-RD, that is TIN, membranous glomerulonephritis (MGN) and other glomerular lesions, and pyelitis, are collectively referred to as IgG4-RKD. Clinically, decreased renal function, or characteristic imaging findings such as multiple low-density lesions on contrast-enhanced computed tomography or diffuse thickening of the renal pelvic wall, are typical presenting features. Although a rapid response to corticosteroid therapy is a very important feature of IgG4-TIN, in cases in which renal function is moderately to severely decreased before therapy, only partial recovery of renal function is obtained.

Summary

TIN with characteristic imaging findings is a typical manifestation of IgG4-RKD in the interstitium, while MGN is a representative manifestation of the glomerular lesions. Although IgG4 is a central feature of IgG4-RD, the recent discovery of IgG4-negative IgG4-RD raises questions about the causative role of the IgG4 molecule in this context.

Membranous nephropathy as a rare renal manifestation of IgG4-related disease

IgG4-related disease, a newly described immune-mediated disorder with tissue infiltration of IgG4-positive plasma cells, has been reported in nearly every organ. In the kidney, it manifests as IgG4-related tubulointerstitial nephritis (TIN) but may also present as membranous nephropathy. We report a patient with IgG4 renal disease who had membranous nephropathy as well as TIN.

An Overlapping Case of Lupus Nephritis and IgG4-Related Kidney Disease

We report a case of a 71-year-old Filipino female who was admitted to the hospital for abdominal pain, vomiting and diarrhea of 8 days duration. The patient was found to have marked acute kidney injury (AKI), which required hemodialysis in the next 3 days. Extensive workup revealed hematuria, subnephrotic range proteinuria, elevated anti-nuclear antibody (ANA) and elevated total immunoglobulin G (IgG) levels, with normal IgG4 and anti-dsDNA levels. On kidney biopsy, mild membranous glomerulonephritis was found, along with autoimmune tubulointerstitial nephritis (TIN) with a “full-house” pattern of immune deposits. These findings were suggestive of lupus interstitial nephritis. However, IgG4+ plasma cells were detected in the interstitium by immunostaining, favoring a diagnosis of IgG4-related kidney disease (IgG4-RKD). Our case highlights the difficulty in differentiating lupus nephritis (LN) from IgG4-RKD in some patients, raising the suspicion that these two entities can co-exist.

Mitochondrial-dependent Autoimmunity in Membranous Nephropathy of IgG4-related Disease

The pathophysiology of glomerular lesions of membranous nephropathy (MN), including seldom-reported IgG4-related disease, is still elusive. Unlike in idiopathic MN where IgG4 prevails, in this patient IgG3 was predominant in glomerular deposits in the absence of circulating anti-phospholipase A₂ receptor antibodies, suggesting a distinct pathologic process. Here we documented that IgG4 retrieved from the serum of our propositus reacted against carbonic anhydrase II (CAII) at the podocyte surface. In patient's biopsy, glomerular CAII staining increased and co-localized with subepithelial IgG4 deposits along the capillary walls. Patient's IgG4 caused a drop in cell pH followed by mitochondrial dysfunction, excessive ROS production and cytoskeletal reorganization in cultured podocytes. These events promoted mitochondrial superoxide-dismutase-2 (SOD2) externalization on the plasma membrane, becoming recognizable by complement-binding IgG3 anti-SOD2. Among patients with IgG4-related disease only sera of those with IgG4 anti-CAII antibodies caused low intracellular pH and mitochondrial alterations underlying SOD2 externalization. Circulating IgG4 anti-CAII can cause podocyte injury through processes of intracellular acidification, mitochondrial oxidative stress and neoantigen induction in patients with IgG4 related disease. The onset of MN in a subset of patients could be due to IgG4 antibodies recognizing CAII with consequent exposure of mitochondrial neoantigen in the context of multifactorial pathogenesis of disease.

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In a patient with IgG4-related disease, glomerular CAII increases and colocalizes with IgG4 deposits.

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IgG4 from patient's serum reacts against CAII expressed by podocytes.

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IgG4 causes acidification, mitochondrial dysfunction and ROS-dependent cytoskeletal alterations in cultured podocytes.

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IgG4 induces the externalization on the plasma membrane of clustered SOD2, becoming recognizable by complement-binding IgG3.

Immunohistological analysis for immunological response and mechanism of interstitial fibrosis in IgG4-related kidney disease

OBJECTIVES

Our study aimed to clarify the immunological characteristics and the mechanism of interstitial fibrosis in immunoglobulin G4-related kidney disease (IgG4-RKD) by the immunohistological analysis.

METHODS

Immunohistological study was performed in the biopsied renal tissues of 16 IgG4-RKD, 16 Sjögren syndrome (SJS), and 17 idiopathic tubulointerstitial nephritis (ITIN) patients using antibodies against IgG; IgG1; IgG4; CD38; CD3; C-X-C chemokine receptor type 3 (CXCR3); chemokine (C-C motif) receptor 4 (CCR4); forkhead box 3 (Foxp3); Type I, Type III, Type IV, and Type VI collagens; and transforming growth factor (TGF)-β1.

RESULTS

Interstitial lymphoplasmacytic and eosinophilic infiltration and the severity of interstitial fibrosis were greater in IgG4-RKD than SJS and ITIN. The ratio of CXCR3+/CD3 + cells was greater in SJS as compared with that in IgG4-RKD and ITIN. The ratio of CCR4+/CD3 + cells was not different among the three diseases. The ratio of interstitial IgG4+/IgG+ plasma cells, Foxp3+/CD3 + cells, and TGF-β1 + cells/total infiltrating cells was higher in IgG4-RKD than SJS and ITIN. There was a positive correlation between the ratio of Foxp3+/CD3 + cells and that of IgG4+/IgG+ plasma cells in IgG4-RKD. Significant correlation was found between the ratio of Foxp3+/CD3 + cells and that of TGF-β1 + cells/total infiltrating cells in IgG4-RKD. Foxp3 + cells and TGF-β1 + cells were colocalized in the interstitium in IgG4-RKD. The significant correlation between the ratio of TGF-β1 + cells/total infiltrating cells and the severity of fibrosis was noticed in IgG4-RKD. The interstitial distribution of type III collagen and type IV collagen was higher in IgG4-RKD than in SJS.

CONCLUSIONS

Our results suggest that regulatory T-cells (Tregs) may play a central role in IgG4 production in the interstitium and TGF-β1 induced by Tregs may play a pivotal role in the interstitial fibrosis including type III and type IV collagens in IgG4-RKD.

Tubulointerstitial fibrosis in patients with IgG4-related kidney disease: pathological findings on repeat renal biopsy

Renal parenchymal lesions in patients with IgG4-related kidney disease (IgG4-RKD) are characterized by tubulointerstitial nephritis with storiform fibrosis and infiltration by high numbers of IgG4-positive plasma cells. The aim of this study was to evaluate the clinical and pathological effects of corticosteroid therapy in patients with IgG4-RKD. Of six patients who were diagnosed with IgG4-RKD, four patients underwent re-biopsy at approximately 30-50 days after corticosteroid therapy was initiated. Based on the classification of Yamaguchi et al., the degree of tubulointerstitial fibrosis was classified before and after therapy. In addition, tubulointerstitial expression patterns of α-smooth muscle actin (α-SMA), collagen I, III, and IV protein, and connective tissue growth factor (CTGF) mRNA were examined. Histopathological findings before treatment showed α-SMA-positive myofibroblasts in the lesion, and CTGF mRNA-positive cells were found in the cellular infiltrate. Although corticosteroid therapy improved serum creatinine clinically, the stage of fibrosis advanced pathologically as evidenced by increased staining for collagen I and III. However, the number of IgG4-positive plasma cells decreased, and CTGF mRNA expression reduced. In other words, fibrosis had advanced from the time of extensive cell infiltration in patients with IgG4-RKD and inflammation was relieved by corticosteroid. A reduced number of positive CTGF mRNA expression cells in repeat biopsies indicated that the fibrosis process was terminated by corticosteroid therapy. We propose that corticosteroid therapy could terminate the pathway of active fibrosis, thereby inhibiting progression to renal dysfunction.

Idiopathic membranous nephropathy and IgG4: an interesting relationship

Idiopathic membranous nephropathy (iMN) is a single-organ autoimmune disease characterized by subepithelial deposition of immune complexes containing IgG4 resulting in proteinuria, nephrotic syndrome, and, in some, end-stage renal disease. The pathogenesis involves a chronic IgG4 response against specific podocyte antigens which have now been at least partially defined in the neonatal, early childhood, and adult varieties. More has recently been learned about the genetic predisposition as well. This review discusses the pathophysiology of iMN in light of these discoveries and what is known about the genesis and potential clinical ramifications of an antigen-specific IgG4 response.

IgG4-Related Tubulointerstitial Nephritis Associated with Membranous Nephropathy in Two Patients: Remission after Administering a Combination of Steroid and Mizoribine

We report two cases of Japanese men who presented with proteinuria, eosinophilia, hypocomplementemia, and high serum immunoglobulin G4 (IgG4) concentration and were diagnosed with membranous nephropathy associated with IgG4-related tubulointerstitial nephritis on renal biopsy. The typical renal lesions of IgG4-related disease are tubulointerstitial nephritis, which improves remarkably with steroid therapy, and occasional glomerular changes. In our two cases, renal biopsy revealed IgG4-positive immune complex deposits in glomeruli in a pattern of membranous nephropathy and concurrent tubulointerstitial nephritis with IgG4 plasma cells. In both cases, proteinuria persisted with initial prednisolone treatment and was resolved only after the addition of mizoribine. We report the first two cases in which the combination of prednisolone and mizoribine was effective for treating membranous nephropathy associated with IgG4-related tubulointerstitial nephritis.

Membranous nephropathy: from models to man

As recently as 2002, most cases of primary membranous nephropathy (MN), a relatively common cause of nephrotic syndrome in adults, were considered idiopathic. We now recognize that MN is an organ-specific autoimmune disease in which circulating autoantibodies bind to an intrinsic antigen on glomerular podocytes and form deposits of immune complexes in situ in the glomerular capillary walls. Here we define the clinical and pathological features of MN and describe the experimental models that enabled the discovery of the major target antigen, the M-type phospholipase A2 receptor 1 (PLA2R). We review the pathophysiology of experimental MN and compare and contrast it with the human disease. We discuss the diagnostic value of serological testing for anti-PLA2R and tissue staining for the redistributed antigen, and their utility for differentiating between primary and secondary MN, and between recurrent MN after kidney transplant and de novo MN. We end with consideration of how knowledge of the antigen might direct future therapeutic strategies.

Pathogenetic role of an autoimmune susceptibility locus derived from MRL/MpJ strain chromosome 1 in chronic pancreas inflammation

We examined the role of Mag, an autoimmune susceptibility locus encoded by the telomeric region of MRL/MpJ mouse chromosome 1, in the pathogenesis of autoimmune exocrinopathy. At nine to 12 months of age, strain-specific differences were observed in the pancreas of the animals. B- and T-cell-containing periductal/perivascular cell infiltrations in the pancreases of MRL/MpJ and B6.MRLc1 congenic C57BL/6-background Mag-carrying strains were more severe than were those of C57BL/6. Pancreatic periductal/perivascular cell infiltration was observed frequently in A/J, AKR/N, B6.MRLc1, C57BL/6, and MRL/MpJ, moderately in DBA/1 and DBA/2, and rarely in BALB/c and C3H/He strains. Females tended to have greater pancreatic periductal/perivascular cell infiltration than males. C57BL/6 mice possessed defined borders between cell infiltrations and acini, but borders were indistinct in MRL/MpJ and B6.MRLc1 mice. We attributed this to the invasion of inflammatory cells between each acinus and the disruption of acinar cells around cell infiltrations in the latter strains. No strain-specific differences were observed in the appearance of fibrotic lesions and high endothelial venules in the cell infiltrates. The levels of serum anti-dsDNA antibodies and amylase, and mRNA expression of tumor necrosis factor-α and Fc gamma receptor III (encoded on Mag) in the pancreases, were elevated in MRL/MpJ- and B6.MRLc1-strain mice relative to C57BL/6. These results emphasized the crucial roles of Mag in the molecular and genetic pathogenesis of autoimmune-mediated pancreatitis.

IgG4-related membranous nephropathy with high blood and low urine IgG4/IgG ratio: a case report and review of the literature

Membranous nephropathy (MN) is a rare manifestation of IgG4-related disease. Interestingly, the significance of IgG4 has also been documented in idiopathic MN (IMN). Previous studies reported that urine IgG4/IgG ratios were significantly higher in IMN compared with other kinds of nephropathy, indicating that impairment of charge selectivity barrier seemed to be an obvious characteristic of IMN. Although high blood concentration of IgG4 is very common in IgG4-related MN, no study about the urine IgG4 has been described before. Here, we present a 55-year-old male with IgG4-related MN. Complete remission of proteinuria was promptly achieved by glucocorticoid treatment without immunosuppressant. Consistent with previous reports, the serum antibody against M-type phospholipase A2 receptor was negative. Surprisingly, although the blood concentration of IgG4/IgG reached as high as 36 %, the urine concentration of IgG4/IgG was only 5 %. The calculated ratio of the renal clearance of IgG4 to IgG of this patient (0.15) was obviously lower than that of five patients with IMN (0.53∼0.81). We speculated that this phenomenon might be a clue of the different pathogenesis between IgG4-related MN and IMN.

IgG4-related kidney disease

IgG4-related kidney disease (IgG4-RKD) is a comprehensive term for renal lesions associated with IgG4-related disease, which is a recently recognized clinical entity characterized by a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells with fibrosis affecting several organs. Tubulointerstitial nephritis with increased IgG4-positive plasma cells and fibrosis is the most dominant feature of IgG4-RKD and may cause acute or chronic renal dysfunction, although some glomerular lesions such as membranous nephropathy are sometimes evident. Radiologically, several characteristic abnormalities are often demonstrated, sometimes mimicking malignancies. IgG4-RKD predominantly affects middle-aged to elderly men, and most patients have accompanying IgG4-related extrarenal lesions such as sialadenitis, lymphadenopathy, or type 1 autoimmune pancreatitis. Serology usually demonstrates high levels of serum total IgG and IgG4, and high levels of serum IgE and hypocomplementemia are also frequent features. Corticosteroid therapy is usually quite effective, leading to amelioration of the renal dysfunction and radiological and serological abnormalities. However, as any delay in treatment may result in irreversible renal failure, early diagnosis and appropriate therapy are very important. Despite these distinctive clinicopathological features of IgG4-RKD, its pathogenesis remains poorly understood. Awareness of this condition and accumulation of more cases worldwide are necessary.

IgG4: a tantalizing link between causes of membranous glomerulonephritis and systemic disease

Alexander et al. give a detailed description of IgG4-related membranous glomerulonephritis (MGN). Their data delineate for the first time in IgG4-related disease (IgG4-RD) a second pattern of tissue injury occurring within the same organ. The paper highlights that MGN can occur alone or simultaneously with IgG4-related tubulointerstitial nephritis. Thus, it extends our understanding of IgG4-RD and illuminates potential pathways for new investigations into its pathophysiology.

Development of IgG4-related disease in a patient diagnosed with idiopathic membranous nephropathy

We report a case of IgG4-related disease (IgG4-RD) diagnosed after 3 years of follow-up for idiopathic membranous nephropathy (MN). MN has been considered as glomerular lesion of IgG4-related kidney diseases in recent years and was diagnosed simultaneously with or after a diagnosis of IgG4-RD in previously reported cases. In the present case, IgG4-RD developed 3 years after the diagnosis of idiopathic MN, indicating a possible relationship between idiopathic MN and IgG4-RD through common underlying mechanisms of development.

Membranous nephropathy associated with type 1 autoimmune pancreatitis and dominant glomerular IgG4 deposit

We report a case of membranous nephropathy associated with type 1 autoimmune pancreatitis. A 58-year-old man presented with anorexia. Work-up revealed a mass in the pancreatic head, which was subsequently resected. Pathological examination showed diffuse infiltration of immunoglobulin (Ig) G4-positive plasma cells, which was compatible with the diagnosis of type 1 autoimmune pancreatitis. Serum IgG4 was elevated. He developed nephrotic syndrome around the time of the surgery. Kidney biopsy confirmed the diagnosis of membranous nephropathy. Immunofluorescent staining showed predominant glomerular IgG4 deposit among IgG subclasses. Tubulointerstitial nephritis, which is usually a dominant feature of renal involvement in IgG4-related disease, was not observed. The patient was treated with prednisolone and several immunosuppressants. During the course, the degree of proteinuria was associated with the serum IgG4 level. Serum antibody against phospholipase A2 receptor was negative. These findings together with IgG4-dominant glomerular deposit suggest that IgG4 may play a unique role in the pathogenesis of secondary membranous nephropathy caused by IgG4-related diseases.

American Society of Nephrology Quiz and Questionnaire 2012: glomerulonephritis

Presentation of the Nephrology Quiz and Questionnaire (NQQ) has become an annual tradition at the meetings of the American Society of Nephrology. It is a very popular session, judged by consistently large attendance. Members of the audience test their knowledge and judgment on a series of case-oriented questions prepared and discussed by experts. They can also compare their answers in real time, using audience response devices, to those of program directors of nephrology training programs in the United States, acquired through an Internet-based questionnaire. The topic presented here is GN. Cases representing this category, along with single best answer questions, were prepared by a panel of experts (Drs. Fervenza, Glassock, and Bleyer). The correct and incorrect answers were then briefly discussed after the audience responses and the results of the questionnaire were displayed. This article recapitulates the session and reproduces its educational value for a larger audience--that of the readers of the Clinical Journal of the American Society of Nephrology. Have fun.

Membranous nephropathy with repeated flares in IgG4-related disease

IgG4-related disease (IgG4-RD) is associated with the infiltration of IgG4-positive plasma cells into various organs. Nephropathy of IgG4-RD is generally interstitial nephritis and glomerulonephritis is rare. We describe a case of membranous nephropathy (MN) without interstitial nephritis associated with IgG4-RD symptoms including lymphadenopathy and pulmonary and pleural lesions. Treatment with steroids improved these clinical symptoms, but withdrawal of steroids induced the repeated relapse of MN. Finally, flaring of MN was prevented by the combination of steroids and cyclosporine. This is the first report of the successful treatment of MN associated with IgG4-RD by this combination therapy.

Membranous glomerulonephritis is a manifestation of IgG4-related disease

IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease that typically manifests as fibro-inflammatory masses that can affect nearly any organ system. Renal involvement by IgG4-RD usually takes the form of IgG4-related tubulointerstitial nephritis, but cases of membranous glomerulonephritis (MGN) have also been described. Here we present a series of 9 patients (mean age at diagnosis 58 years) with MGN associated with IgG4-RD. All patients showed MGN on biopsy, presented with proteinuria (mean 8.3 g/day), and most had elevated serum creatinine (mean 2.2 mg/dl). Seven patients had known extrarenal involvement by IgG4-RD, with 5 patients having concurrent IgG4-related tubulointerstitial nephritis. Immunohistochemical analysis for the phospholipase A2 receptor, a marker of primary MGN, was negative in all 8 biopsies so examined. Six of 7 patients with available follow-up (mean 39 months) were treated with immunosuppressive agents; one untreated patient developed end-stage renal disease and underwent transplantation, without recurrence at 12 years after transplant. All 6 treated patients showed decreased proteinuria (mean 1.2 g/day), and most showed decreased serum creatinine (mean 1.4 mg/dl). Thus, MGN should be included in the spectrum of IgG4-RD and should be suspected in proteinuric IgG4-RD patients. Conversely, patients with MGN and an appropriate clinical history should be evaluated for IgG4-RD.

IgG4-related kidney disease

IgG4-related kidney disease is a term that refers to any form of renal involvement by IgG4-related disease (IgG4-RD), a recently recognized systemic immune-mediated disease. The most common renal manifestation is IgG4-related tubulointerstitial nephritis (IgG4-TIN), which presents as acute or chronic renal insufficiency, renal mass lesions, or both. On biopsy, IgG4-TIN shows a plasma cell-rich interstitial inflammatory infiltrate with increased IgG4+ plasma cells, along with expansile interstitial fibrosis; tubular basement membrane immune complex deposits are common. IgG4-TIN usually shows a brisk response to immunosuppressive therapy. Glomeruli may be affected by IgG4-RD, usually in the form of membranous glomerulonephritis. Other patterns of glomerular disease include IgA nephropathy, membranoproliferative glomerulonephritis, and endocapillary or mesangioproliferative immune complex glomerulonephritis. IgG4-related plasma cell arteritis has also been observed in the kidney. This review describes the histopathologic and immunophenotypic patterns of renal involvement by IgG4-RD, with associated clinical, radiographic, and serologic features.

IgG4-related tubulointerstitial nephritis with plasma cell-rich renal arteritis

Immunoglobulin G4 (IgG4)-related tubulointerstitial nephritis is a newly recognized clinicopathologic entity that may occur as an isolated renal lesion or as part of a multisystem disorder. It is characterized by plasma cell-rich interstitial nephritis with abundant IgG4-positive plasma cells and IgG-dominant tubulointerstitial immune deposits. We report the first case of IgG4-related tubulointerstitial nephritis with multifocal plasma cell-rich renal arteritis presenting as acute kidney injury in a 72-year-old man. Seven weeks of prednisone therapy led to nearly complete recovery of kidney function. This case enlarges the morphologic spectrum of this disorder and emphasizes the need to distinguish it from other causes of renal vasculitis.

Immunohistochemical Characteristics of IgG4-Related Tubulointerstitial Nephritis: Detailed Analysis of 20 Japanese Cases

Although tubulointerstitial nephritis with IgG4+ plasma cell (PC) infiltration is a hallmark of IgG4-related kidney disease (IgG4-RKD), only a few studies are available about the minimum number of IgG4+ PC needed for diagnosis along with IgG4+/IgG+ PC ratio in the kidney. In addition, the significance of the deposition of IgG or complement as a reflection of humoral immunity involvement is still uncertain. In this study, we analyzed 20 Japanese patients with IgG4-RKD to evaluate the number of IgG4+ PCs along with IgG4+/IgG+ PC ratio and involvement of humoral immunity. The average number of IgG4+ PCs was 43.8/hpf and the average IgG4+/IgG+ or IgG4+/CD138+ ratio was 53%. IgG and C3 granular deposits on the tubular basement membrane (TBM) were detected by immunofluorescence microscopy in 13% and 47% of patients, respectively. Nine patients had a variety of glomerular lesions, and 7 of them had immunoglobulin or complement deposition in the glomerulus. In conclusion, we confirmed that infiltrating IgG4+ PCs > 10/hpf and/or IgG4/IgG (CD138)+ PCs > 40% was appropriate as an item of the diagnostic criteria for IgG4-RKD. A relatively high frequency of diverse glomerular lesions with immunoglobulin or complement deposits and deposits in TBM may be evidence of immune complex involvement in IgG4-related disease.

IgG4-Related Disease Is Not Associated with Antibody to the Phospholipase A2 Receptor

Patients with IgG4-related disease (IgG4-RD) share histopathological characteristics that are similar across affected organs. The finding of infiltration with IgG4+ plasma cells in the proper clinical and histopathological contexts connects a large number of clinical entities that were viewed previously as separate conditions. The renal involvement in IgG4-RD is usually characterized by tubulointerstitial nephritis, but membranous nephropathy has also been reported to be one of the renal complications of IgG4-RD. The recent discovery that a high proportion of patients with idiopathic membranous nephropathy (IMN) have IgG4 autoantibodies to the M-type phospholipase A2 receptor (PLA2R) in the circulation and glomerular immune deposits, together with the profound IgG4 hypergammaglobulinemia and occasional reports of membranous nephropathy in IgG4-RD, raised the question of a common antigen. To assess the presence of anti-PLA2R antibody in patients with IgG4-RD, we screened sera from 28 IgG4-RD patients by immunoblot. None of the patients in this cohort had detectable circulating anti-PLA2R antibodies. This study suggests that despite some clinical and serological overlaps between IgG4-RD and IMN,anti-PLA2R antibodies do not play a role in the pathogenesis of IgG4-RD. Additional studies of IgG4-RD with evidence of membranous nephropathy are important to exclude any definite relationship.

[IgG4-related disease and renal and urological involvement]

Hyper-IgG4 syndrome, or IgG4-related disease, is an emerging disorder, involving one or more organ(s), and characterized by "storiform" fibrosis and inflammatory lesions with a predominance of IgG4+ plasma cells and increased IgG4 serum levels. Since the first report of auto-immune pancreatitis, numerous organ lesions have been reported and have been found to occur in a same patient including: sialadenitis, dacryoadenitis, lymphadenopathy, liver and biliary tract involvement, and renal and retroperitoneal lesions. Renal involvement was first described in 2004 and usually presents as functional and/or morphological abnormalities. In most cases, renal pathological analysis reveals tubulointerstitial nephritis that is rarely associated with glomerular lesions. Retroperitoneal fibrosis is also a typical feature that may be associated with periaortitis or inflammatory abdominal aortic aneurysm. First line treatment is based on corticosteroid therapy. Short-term outcome is usually favorable. However, patients should be carefully monitored for relapses and long-term complications. Although the multiple organ lesions share common clinical, biological, radiological and pathological features, no consensus diagnostic criteria have yet been validated for IgG4-related disease. Ruling out differential diagnoses is thus mandatory. Our literature review provides nephrologists, urologists and pathologists with key elements that will help in the early diagnosis and proper management of this new and emerging disorder.

The latest on IgG4-RD: a rapidly emerging disease

PURPOSE OF REVIEW

Provide an update of the developments in IgG4 related disease within the last year in terms of nomenclature, diagnostic criteria and clinical features.

RECENT FINDINGS

The number of diseases associated with IgG4 related disease continues to grow. The entities of idiopathic orbital inflammation, idiopathic cervical fibrosis, eosinophilic angiocentric fibrosis, reactive nodular fibrous pseudotumor, sclerosing mesenteritis, and membranous glomerulonephritis should all be added to the list of diseases associated with the IgG4 related disease spectrum. The issues of nomenclature and diagnostic criteria for IgG4 related disease have important recent developments as well.

SUMMARY

The diagnosis of IgG4 related disease continues to be challenging. Increasing recognition of IgG4 related disease has led to a large body of literature on organ sites of involvement. Understanding how the disease manifests itself is critical to diagnosis and ultimately treatment.