An abundance of IgG4+ plasma cells is not specific for IgG4-related tubulointerstitial nephritis

Immunohistological analysis reveals IgG1-dominant immunophenotype of tubulointerstitial nephritis unassociated with IgG4-related diseases

PURPOSE

Tubulointerstitial nephritis (TIN) has various etiologies, including IgG4-related disease (IgG4-RD), autoimmune diseases, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), and others. IgG4-positive plasma cell infiltration can occasionally be found in TIN unrelated to IgG4-RD. Therefore, there may be problems with usage of IgG4 immunostaining to differentiate between TIN with and TIN without IgG4-RD. This study aimed to compare the proportion of plasma cells that are positive for each IgG subclass and to clarify the predominant IgG subclass trends and clinical characteristics associated with IgG4-RD and non-IgG4-related interstitial nephritis.

METHODS

The study enrolled 44 cases of TIN: 6 of IgG4-RD, 8 of autoimmune disease, 9 of AAV, and 21 of unknown disease group. In addition to clinical characteristics, IgG subclass composition of interstitial plasma cells was evaluated among 4 groups by immunohistochemistry.

RESULTS

IgG1 was the predominant IgG subclass in TIN unrelated to IgG4-RD. In the IgG4-RD group, the IgG subclass rate was high in both IgG1 and IgG4. The rate of average IgG4-positive cells was significantly lower in the autoimmune disease group and unknown disease group compared with the IgG4-RD group.

CONCLUSION

The present study revealed IgG1-dominant immune profiles of TIN unrelated to IgG4-RD. Further investigation is required to elucidate the clinicopathological differences between IgG1-dominant and IgG4-dominant groups in IgG4-RD.

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).

ANCA-associated kidney disease preceded by orbital pseudotumor

INTRODUCTION

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and IgG4-related disease (IgG4-RD) are distinct immune disorders with overlapping clinical and laboratory features. While ANCA positivity excludes IgG4-RD in the 2019 ACR/EULAR classification, this criterion is not uniformly applied, and AAV can form inflammatory masses in various organs and show increase in IgG4 + plasma cells, similar to IgG4-RD.

CASE DIAGNOSIS/TREATMENT

A 5-year-old female with history of orbital mass diagnosed as IgG4-RD presents with acute kidney injury. She has a myeloperoxidase ANCA, and kidney biopsy shows pauci-immune crescentic glomerulonephritis and acute tubulointerstitial nephritis with increased IgG4 + plasma cells and tubular basement membrane (TBM) deposits.

CONCLUSION

In isolation, TBM deposits and increased IgG4 + plasma cells are suggestive of IgG4-RD. In the context of a positive ANCA and pauci-immune crescentic glomerulonephritis, however, increased IgG4 + plasma cells due to AAV are favored. In cases with features of IgG4-RD, ANCA positivity suggests an alternate diagnosis of AAV to be more likely.

Utility of CD138/syndecan-1 immunohistochemistry for localization of plasmacytes is tissue-dependent in B6 mice

Objective

Inflammation is present in many diseases and identification of immune cell infiltration is a common assessment. CD138 (syndecan-1) is a recommended immunohistochemical marker for human plasmacytes although it is also expressed in various epithelia and tumors. Similarly, CD138 is a marker for murine plasmacytes, but its tissue immunostaining is not well-defined. Endogenous CD138 expression is an important confounding factor when evaluating plasmacyte infiltration. We studied two plasmacyte markers (CD138 and Kappa light chains) for endogenous immunostaining in five organs and one tumor from B6 mice.

Results

Plasmacytes in Peyer’s patches were positive for CD138 and Kappa markers without endogenous immunostaining. Endogenous CD138 immunostaining was widespread in liver, kidney, lung and a malignant peripheral nerve sheath tumor (MPNST) versus regionalized immunostaining in skin and small intestine wall. Endogenous Kappa immunostaining was absent in all tissues except for plasmacytes. Tissues with widespread endogenous CD138 immunostaining were contrasted by absence of endogenous Kappa immunostaining. Here, plasmacytes would not be distinguished by CD138, but would be obvious by Kappa immunostaining. Our study suggests that utility of immunostaining for plasmacytes by CD138 is tissue dependent in mice. Additionally, Kappa immunostaining may be a useful alternative in mouse tissues with confounding endogenous CD138 immunostaining.

A case of simultaneous onset of highly active systemic lupus erythematosus and IgG4-related renal disease

The patient was a 73-year-old woman who had hair loss, purpura, and numbness of the soles for past 1 year. Three months prior, she was diagnosed with interstitial lung disease (ILD) and was admitted to our department. She was diagnosed with systemic lupus erythematosus (SLE) based on positive antinuclear antibodies 1280× (speckled type), hair loss, low white blood cell count, positive anti-cardiolipin and anti-ds-DNA antibodies, and lupus retinopathy. In addition, the patient was also diagnosed with immunoglobulin G (IgG)4-related disease (IgG4RD) based on high serum IgG4 levels, ILD, urine occult blood, protein, and cast, and renal histological findings showed endocapillary proliferative glomerulonephritis, increased IgG4 positive plasma cells, and characteristic storiform fibrosis. High-dose glucocorticoid therapy, hydroxychloroquine, and belimumab were administered, which improved the SLE symptoms of lupus retinopathy and peripheral neuropathy, as well as the IgG4RD symptoms of ILD and urinary findings. Herein, we report a rare case of simultaneous onset of IgG4-related nephropathy with active glomerular lesions and SLE, in which renal histology, including fluorescent antibodies, was crucial for diagnosis.

[Basic nephropathology for pathologists-part 1 : Kidney biopsy-inflammation and immune complexes]

The assessment of kidney biopsies is mainly confined to specialized centres. However, sometimes a kidney biopsy is submitted to a general pathologist, and in addition peritumorous renal parenchyma in tumour nephrectomies can have concomitant non-neoplastic renal disease. Here we present a survey of inflammatory and immunologic changes in all renal compartments, which may in part indicate the need of prompt therapeutic intervention such as in vasculitis, glomerulonephritis and interstitial nephritis. It is important to take into account that renal involvement of vasculitis is mainly centred in glomeruli and only to a much lesser extent in arteries, and that the frequently observed interstitial inflammation very often is an epiphenomenon of another primary kidney disease and not an independent disease process. Typical renal patterns of injury are emphasised.

ANCA-associated vasculitis and IgG4-related disease overlap syndrome: a case report and literature review

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides are infrequent autoimmune diseases characterized by inflammation of the walls of small vessels leading to tissue and endothelial damage. On the other hand, IgG4-related disease is a fibroinflammatory disease characterized histologically by lymphoplasmacytic infiltrates with IgG4+ plasma cells, storiform fibrosis, and obliterative phlebitis that may affect nearly every organ of the body. There are similarities in clinical, serological, radiological, and histopathological features between both diseases, and hence, they usually mimic each other complicating the differential diagnosis. Furthermore, reports of patients with the coexistence of both conditions (overlap syndrome) have been reported. We herein report a patient with an unequivocal diagnosis of ANCA-associated vasculitis, specifically granulomatosis with polyangiitis (posterior uveitis, polyneuropathy, pauci-immune glomerulonephritis with crescent formation and granulomas, and MPO-ANCA positivity) and IgG4-related disease (thoracic aortitis, tubulointerstitial nephritis with prominent IgG4+ plasma cell infiltration, fibrosis, and obliterative arteritis, high levels of serum IgG4, and eosinophilia) overlap syndrome.

Eosinophilic granulomatosis with polyangiitis exhibits T cell activation and IgG4 immune response in the tissue; comparison with IgG4-related disease

Objective

To study the pathophysiological differences of EGPA and IgG₄-related disease (RD) by clarifying their clinical, pathological and immunological features.

Methods

Clinical and pathological findings were compared in patients with EGPA and IgG₄-RD. Peripheral blood mononuclear cells were used for comprehensive flow cytometric analysis.

Results

An elevation of the IgG4 level was found in all EGPA cases, with the accompanying pathological findings of lymphocytic infiltration and fibrosis observed in 30.8% patients, and the elevation of IgG₄/IgG ratio in 61.5% patients. However, actual IgG₄ levels, as well as the degree of the infiltration of IgG₄-positive plasma cells, were still higher in patients with IgG₄-RD than patients with EGPA. Examination by ACR/EULAR classification criteria showed only 13.6% of the EGPA patients met entry criteria, while all of them met the exclusion criteria. In regard to the immunophenotyping, EGPA patients had increases in activated CD4 and CD8 T cells compared with the healthy controls. However, no such similar changes occurred in IgG₄-RD patients. On the other hand, both the EGPA and IgG₄-RD patient groups had correlated increased plasmablasts and Tfh. These results indicate the presence of two axes: namely, the activation of T cells and that of B cells. Both axes are present in EGPA, but the T cell activation axis was not observed in IgG₄-RD.

Conclusions

The elevation of serum IgG₄ as well as pathological IgG₄ infiltration are not specific. Meanwhile, EGPA and IgG4-RD differ in immunological phenotypes, indicating the possible importance of the predominant activation of T cells in the development of vasculitis.

A case of eosinophilic granulomatosis with polyangiitis as a mimicker of IgG4-related disease

A 62-year-old woman was admitted to our hospital because of fever, renal dysfunction, eosinophilia, and the presence of MPO-ANCA. Based on the renal pathological examination which showed granuloma lesion with eosinophils and crescentic glomerulonephritis, eosinophilic granulomatosis with polyangiitis (EGPA) was diagnosed. On the other hand, laboratory examination showed elevated serum IgG4 levels and renal pathological examination showed marked lymphoplasmacytic infiltration and fibrosis surrounding nest "Bird's eye pattern," which were characteristic of IgG4-related kidney disease (IgG4-RKD). Because there are cases when EGPA has clinical features of IgG4-RKD, we should be careful about diagnoses of IgG4-RKD in patients with EGPA.

An unusual presentation of propylthiouracil-induced anti-MPO and PR3 positive ANCA vasculitis with associated anti-GBM antibodies, IgA nephropathy and an IgG4 interstitial infiltrate: a case report

Background

A number of disease processes can culminate in rapidly progressive glomerulonephritis, including pauci-immune focal segmental necrotising glomerulonephritis, usually seen with positive serum antineutrophil cytoplasmic antibodies (ANCA). Propylthiouracil (PTU) has been associated with drug-induced ANCA-associated vasculitis (AAV), with antibodies against myeloperoxidase (MPO) and proteinase 3 (PR3) present individually and together having been recognised. ‘Double-positive’ vasculitis with ANCA and anti-glomerular basement membrane (GBM) antibodies has also been reported in association with PTU treatment. We present a case of PTU-induced anti-MPO and PR3 positive ANCA vasculitis with associated anti-GBM antibodies, IgA nephropathy and an IgG4 interstitial infiltrate.

Case presentation

A 51-year-old man presented 2 weeks after re-commencing propylthiouracil (PTU) treatment for Graves’ disease, with a severe acute kidney injury and haemato-proteinuria. He demonstrated positive titres for autoantibodies to PR3 (76.9 IU/mL), MPO (28.8 IU/mL) and GBM (94 IU/mL). Renal biopsy demonstrated numerous glomerular crescents, widespread IgG4-positive lymphoplasmacytic infiltrate and mesangial positivity for IgA. PTU was stopped and he was treated with steroids, plasma exchange and cyclophosphamide with sustained improvement in his renal function.

Conclusions

This case of drug-induced AAV presented a unique and intriguing collection of serological and histological features. We propose that the PTU-induced AAV resulted in epiphenomena of anti-GBM antibody production and an IgG4-cell-rich tubulointerstitial infiltrate. It is uncertain whether the mesangial IgA deposition preceded or resulted from the AAV.

Acute Tubulointerstitial Nephritis as a Sole Manifestation of Immunoglobulin G4-Related Disease

This is a case report of a patient who developed severe acute kidney disease with kidney biopsy showing interstitial nephritis, plasma cell infiltration and immunoglobulin G4 (IgG4) expression consistent with IgG4-related kidney disease. There were no other systemic features of IgG4-related disease. The patient was treated with corticosteroids and mycophenolate. This case highlights the need to consider IgG4-related kidney disease even in the absence of other systemic features. Isolated renal involvement is underrecognized and can lead to missed diagnosis. It also illustrates that mycophenolate can be used as a steroid sparing agent in this condition; an observation that adds to the limited literature in this field.

Anti-LRP2 Nephropathy With Abundant IgG4-Positive Plasma Cells: A Case Report

In older adults, the most common kidney biopsy diagnoses include pauci-immune crescentic glomerulonephritis, membranous nephropathy, and focal segmental glomerulosclerosis. Recently, investigators described a small series of older patients (aged 66-80 years) with acute kidney injury and a kidney biopsy demonstrating tubular basement membrane (TBM) immune deposits of polytypic immunoglobulin G (IgG) and C3, acute tubular injury, and tubulointerstitial inflammation. They identified a circulating antibody against kidney tubular low-density lipoprotein (LDL) receptor-related protein 2 (LRP2; also known as megalin) in patients' sera and colocalization of LRP2 with IgG in TBM deposits. We present a rare case of anti-LRP2 nephropathy/anti-brush border antibody disease and describe the novel feature of abundant IgG4-positive interstitial plasma cells. Along with the combination of TBM deposits, tubulointerstitial nephritis (TIN), and segmental glomerular subepithelial immune deposits seen in both entities, this newly described feature adds to the morphologic overlap with IgG4-related TIN. Identification of large TBM deposits using light microscopy and IgG staining of apical aspects of proximal tubules using immunofluorescence microscopy can point to the correct diagnosis of anti-LRP2 nephropathy and prompt confirmatory studies. Particularly in older patients with immune complex-mediated TIN who lack clinical, laboratory, radiographic, and/or characteristic histologic features of IgG4-TIN or other autoimmune, infectious, or drug-related injury, a diagnosis of anti-LRP2 nephropathy should be considered.

New insights into immune cells cross-talk during IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a newly acknowledged entity, characterized by an immune-mediated fibro-inflammatory process affecting virtually all organs, with infiltration of IgG4⁺ bearing plasma cells. Until today the pathogenesis of IgG4-RD remains unknown. Treatment with anti-CD20 monoclonal antibodies efficiently induced remission and attenuated the secretory phenotype of myofibroblasts responsible of uncontrolled collagen deposition. This supports the pathogenic role of the adaptive immunity, particularly B cell compartment and B cell/T cell interaction. Latest studies have also highlighted the importance of innate immune system that has been underestimated before and the key role of a specific T cell subset, T follicular helper cells that are involved in IgG4-class-switching and plasmablast differentiation. In this review, we aim to review the most recent knowledge of innate immunity, T and B cells involvement in IgG4-RD, and introduce tertiary lymphoid organs (TLO) as a potential marker of relapse in this condition.

IgG4-related disease: review of the histopathologic features, differential diagnosis, and therapeutic approach

Immunoglobulin G4-related disease (IgG4-RD) is an uncommon disorder that demonstrates characteristic clinicopathologic features including sclerosing lesions with storiform fibrosis, increased IgG4+ plasma cells with an increased IgG4+/IgG+ plasma cell ratio, obliterative phlebitis, and often an increased serum IgG4 level. This review summarizes the characteristic histopathologic and clinical features of IgG4-RD with detailed discussion of the histopathologic characteristics of the most commonly involved anatomic sites. We also present recent advances in our understanding of the pathophysiologic mechanisms of IgG4-RD and discuss updates on the treatment, prognosis, and outcomes of this rare disease, including discussion of the possible association between IgG4-RD and malignancy.

Diagnostic sensitivity of cutoff values of IgG4-positive plasma cell number and IgG4-positive/CD138-positive cell ratio in typical multiple lesions of patients with IgG4-related disease

OBJECTIVES

This study aimed to investigate the diagnostic sensitivity of the cutoff values of IgG4-positive plasma cell (PC) number and IgG4-positive/CD138-positive cell ratio proposed by the International consensus statement (ICS) on the pathology of IgG4-related disease (IgG4-RD) in typical multiple lesions of patients with IgG4-RD.

METHODS

We evaluated IgG4-positive PC number and IgG4-positive/CD138-positive cell ratio in 39 samples from 18 IgG4-RD patients having more than two typical lesions of IgG4-RD.

RESULTS

We evaluated 12 submandibular, 12 ophthalmic, six skin, five kidney, two pancreatic, and one bronchus and prostate lesion each in 18 patients with typical clinical, serological, and radiographic features. Concerning IgG4 + PC number per high-power field, most ophthalmic (11/12), kidney (5/5), pancreatic (2/2), and bronchial lesions (1/1) fulfilled the cutoff value of ICS, whereas many of the submandibular (6/12) and skin lesions (0/6) did not. In contrast to the absolute number, all lesions fulfilled the cutoff value of IgG4+/CD138 + cell ratio. In eight cases, only one or two lesions in the same patient fulfilled the cutoff value of ICS, while the others did not.

CONCLUSIONS

These results suggest that ICS criteria have different sensitivities among the affected organs for the diagnosis of IgG4-RD.

Concurrent IgG4-related tubulointerstitial nephritis and IgG4 myeloperoxidase-anti-neutrophil cytoplasmic antibody positive crescentic glomerulonephritis: A case report

RATIONALE

IgG4-related disease (IgG4-RD) is a newly recognized systemic disease. The typical pathological finding in the kidney is abundant IgG4-positive plasma cell infiltration with characteristic storiform fibrosis in the interstitium. Antibodies of the IgG4 subclass have been linked to certain autoimmune diseases including antiproteinase 3 (PR3) anti-neutrophil cytoplasmic antibody (ANCA) of the IgG4 subclass. Here, we report a rare case of kidney injury with concurrent typical IgG4-related tubulointerstitial nephritis and IgG4 subclass of myeloperoxidase (MPO) ANCA-positive necrotizing crescentic glomerulonephritis.

PATIENT CONCERNS

A 42-year-old Chinese man presented with repeated epigastric pain, sausage-shaped pancreas observed morphologically in computed tomography, effectiveness of prednisone therapy and was diagnosed with autoimmune pancreatitis. He subsequently developed acute kidney injury.

DIAGNOSES

The patient had an elevated serum IgG4, eosinophilia, and positive MPO-ANCA of IgG4-dominant subclass. Renal biopsy revealed necrotizing crescentic nephritis and typical IgG4-related tubulointerstitial nephritis.

INTERVENTIONS

The patient was treated with a combination of corticosteroids and cyclophosphamide, and a course of rituximab was later added to deplete peripheral B cells.

OUTCOMES

The patient responded well and his renal function improved.

LESSONS

This is the first case report of an IgG4-RD with concurrent IgG4-related tubulointerstitial nephritis and IgG4 MPO-ANCA-associated necrotizing crescentic glomerulonephritis. It raises the difficulty in differentiation diagnosis of the two separate diseases that is worthy of further study.

The incidence of IgG4-positive plasma cells staining TIN in patients with biopsy-proven tubulointerstitial nephritis

AIM

IgG4 disease is rare. However, IgG4 tubulointerstitial nephritis (TIN) is the most common renal manifestation. IgG4 disease is usually associated with elevated serum IgG4 levels and other organ involvement, low-density renal lesions on enhanced CT imaging and immune activation. The incidence of IgG4-TIN may be underestimated, as staining for IgG4 is not routine. This study sought to describe the prevalence of previously undiagnosed IgG4-TIN. Due to the complexity of the diagnosis, we only attempt to look at IgG4-positive plasma cell TIN as a potential indication for IgG4 renal disease.

METHODS

A retrospective review of native renal biopsies performed between 2002 and 2012 with a primary diagnosis of TIN was selected. Samples for which interstitial nephritis was secondary to a glomerular disease were excluded. The tissues were stained for IgG4 and scored by two blinded observers. Demographic and follow-up details were collected. This study was approved by the local ethics committee.

RESULTS

82 cases of interstitial nephritis from a total of 1238 renal biopsies (2002-2012) were available after staining for further assessment. 12 samples demonstrated staining consistent with the criteria for IgG4-positive plasma cell TIN, of which 3 had mildly positive staining, 7 moderately positive staining and 2 had markedly positive staining. There were no statistically significant differences in the baseline characteristics between the positive and negative staining groups.

CONCLUSIONS

A number of cases of IgG4-positive plasma cell TIN were observed histologically that had been previously diagnosed as non-specific chronic TIN. IgG4-positive plasma cell TIN made up 1% of all renal biopsies performed over 10 years and 13% of all biopsies demonstrating TIN not related to glomerular disease. IgG4 staining should be considered routinely in biopsies demonstrating primary TIN.

Multicentric Castleman Disease With Tubulointerstitial Nephritis Mimicking IgG4-related Disease: Two Case Reports

Multicentric Castleman disease is a benign lymphoproliferative disorder with heterogenous clinical symptoms and involves systemic organs in addition to lymph nodes. Elevated serum IgG4 levels and IgG4-positive plasma cell (IgG4+PC) infiltrates have been reported in lymph nodes, lung and skin in some multicentric Castleman disease cases, resembling IgG4-related disease (IgG4-RD) histologically. However, no report has been available regarding IgG4+PC infiltration in the kidneys of multicentric Castleman disease. Here, we report 2 cases of multicentric Castleman disease complicated by IgG4-related disease (IgG4-RD) histologically. However, there has been no report published on PC-rich tubulointerstitial nephritis, lymphadenopathy, with numerous IgG4+PC infiltration, and elevated serum IgG4 levels, mimicking IgG4-RD. The blood examinations revealed systemic inflammation and elevated C-reactive protein and interleukin-6 levels. Corticosteroid therapy was partially effective in both cases, and combination therapy of corticosteroid and tocilizumab was needed in both cases. Moreover, after triple therapy with corticosteroid, rituximab and cyclophosphamide were used in 1 case to tame the severe inflammation. The present cases suggest that if continuously elevated serum C-reactive protein levels and partial corticosteroid responsiveness are encountered, multicentric Castleman disease should be considered rather than IgG4-RD as a differential diagnosis even if serum IgG4 is elevated and IgG4+PCs infiltrate systemic organs.

Recognizing IgG4-related tubulointerstitial nephritis

PURPOSE OF THE REVIEW

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder affecting nearly all organs, including the kidney. Tubulointerstitial nephritis (IgG4-TIN) is the most common form of IgG4-related kidney disease (IgG4-RKD) and is the focus of this concise review.

OBJECTIVE

The study aims to describe when IgG4-TIN should be suspected and to summarize the diagnosis, treatment, and natural history of the disease.

SOURCES OF INFORMATION

Ovid MEDLINE, Google Scholar, and PubMed were searched for full-text English language articles up to January 2016. References included in the manuscript were chosen at the authors' discretion based on their relevance to the subject of the review.

FINDINGS

IgG4-TIN should be considered in patients presenting with abnormal urinalysis, abnormal kidney function, renal lesions on imaging, and elevated IgG, IgE, or hypocomplementemia. Diagnosis of IgG4-TIN requires a combination of histologic features (plasma cell-enriched TIN with >10 IgG4+ plasma cells/hpf, +/- TBM immune complex deposits in many cases) and at least one of the following:Characteristic radiologic findings (small peripheral low-attenuation cortical nodules, round or wedge-shaped lesions, or diffuse patchy involvement)Elevated serum IgG4 levelCharacteristic findings of IgG4-RD in other organs Other conditions such as lupus, vasculitis, diabetic nephropathy, and lymphoma must be excluded, as these can also present with IgG4+ plasma cells in the renal parenchyma. IgG4-TIN is generally responsive to steroids and B cell depletion with rituximab, but relapses are common and patients require close long-term follow-up.

LIMITATIONS

Available data on IgG4-TIN are from retrospective observational studies.

IMPLICATIONS

IgG4-TIN is a distinct and emerging subtype of interstitial nephritis. Nephrologists must be aware of this entity and how to definitively diagnose and treat it. Prospective studies and ideally multi-center clinical trials are needed to study the epidemiology, treatment, and natural history of this disease.

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.

IgG4-related disease: description of a case with pulmonary lesions, mediastinal lymphadenopathies and rapidly progressive renal failure

This is a case report of a 73-year-old man with new-onset acute renal failure while being investigated for pulmonary infiltrates and mediastinal lymphadenopathies. Urine tests showed tubular range proteinuria with no microhaematuria. Immunology tests showed elevated serum IgG and hypocomplementaemia (classical pathway activation). Renal biopsy and clinical-pathological correlation were crucial in this case, reinforcing their important role in the final diagnosis of acute kidney injury.

Evaluation of diagnostic criteria for IgG4-related tubulointerstitial nephritis

Background

IgG4-TIN is the most common pattern of renal involvement in IgG4-related disease. There are several proposed diagnostic criteria of IgG4-TIN recently. Two of them proposed by the Mayo Clinic and JSN are predominant. However, histopathological criteria of the number of IgG4+ plasma cells and several histological features are still under discussion due to low amount of tissue in renal biopsy specimens and low frequency of this kind of specimens. We aimed to screen IgG4-TIN on archived renal biopsy samples and evaluated the application of two proposed diagnostic criteria.

Methods

We selected 480 interstitial inflammation samples for light and electron microscopy and immunohistochemistry of CD138, IgG and IgG4 test. The Mayo Clinic proposed criteria diagnosed high-probability IgG4-TIN and JSN criteria confirmed IgG4-TIN.

Results

Twelve high-probability IgG4-TIN were screened by histology, imaging, serology and other organ involvement according to the Mayo Clinic proposed criteria. The previous principal pathological diagnoses were IgAN (n=4), CreGN (n=4), tubulointerstitial nephritis (n=3) and LN (n=1). Three cases showed storiform fibrosis and a bird’s eye pattern. The distribution of IgG4+ plasma cells was focal, multifocal or diffuse, with a mixed mild, moderate or strong stainingpattern. Their treatment and clinical outcomes varied depending on different levels of proteinuria, serum creatinine, eGFR and original glomerular disease presentation. Therefore, we applied strict histological criteria of storiform fibrosis and evenly distributed IgG4+ plasma cells by JSN to confirm typical IgG4-TIN. Two cases were finally diagnosed as real IgG4-TIN. One was previously diagnosed as idiopathic interstitial nephritis with rapid response to corticosteroid therapy. The other was CreGN with immune complex deposits, which had poor outcome and long-term hemodialysis.

Conclusions

IgG4-TIN might present concurrently with glomerular disease. The proposed criteria by the Mayo Clinic is flexible, sensitive, and superior in the identification of early-stage or atypical IgG4-TIN, with enhanced risk of misdiagnosis as compared to the proposed criteria by JSN, which is stricter, more specific, and might overlook early-stage or atypical IgG4-TIN. We propose a new set of criteria to improve pathologist-derived diagnosis.

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.

IgG4 immunostaining and its implications in orbital inflammatory disease

Objective

IgG4-related disease is an emerging clinical entity which frequently involves tissue within the orbit. In order to appreciate the implications of IgG4 immunostaining, we analyzed gene expression and the prevalence of IgG4- immunostaining among subjects with orbital inflammatory diseases.

Methods

We organized an international consortium to collect orbital biopsies from 108 subjects including 22 with no known orbital disease, 42 with nonspecific orbital inflammatory disease (NSOI), 26 with thyroid eye disease (TED), 12 with sarcoidosis, and 6 with granulomatosis with polyangiitis (GPA). Lacrimal gland and orbital adipose tissue biopsies were immunostained for IgG4 or IgG secreting plasma cells. RNA transcripts were quantified by Affymetrix arrays.

Results

None of the healthy controls or subjects with TED had substantial IgG4 staining. Among the 63 others, the prevalence of significant IgG4-immunostaining ranged from 11 to 39% depending on the definition for significant. IgG4 staining was detectable in the majority of tissues from subjects with GPA and less commonly in tissue from subjects with sarcoidosis or NSOI. The detection of IgG4+ cells correlated with inflammation in the lacrimal gland based on histology. IgG4 staining tissue expressed an increase in transcripts associated with inflammation, especially B cell-related genes. Functional annotation analysis confirmed this.

Conclusion

IgG4+ plasma cells are common in orbital tissue from patients with sarcoidosis, GPA, or NSOI. Even using the low threshold of 10 IgG4+ cells/high powered field, IgG4 staining correlates with increased inflammation in the lacrimal gland based on histology and gene expression.

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.

A case of ANCA-negative renal small-vessel vasculitis with tubulointerstitial infiltration of IgG4-positive plasma cells

A 62-year-old male patient presented with progressive renal dysfunction for 2 months. He had elevated serum C-reactive protein and IgG4 levels with absence of anti-neutrophil cytoplasmic antibodies. A renal biopsy showed severe tubulointerstitial nephritis (TIN) with extensive infiltration of IgG4-positive plasma cells, suggesting a diagnosis of IgG4-related kidney disease (IgG4-RKD). However, the identification of a few crescentic glomeruli and necrotizing vasculitis of an interlobular artery lead to a diagnosis of renal small-vessel vasculitis. This case indicates that a careful examination is required to distinguish between IgG4-RKD and TIN caused by renal small-vessel vasculitis.

Primary Sjögren's syndrome with chronic tubulointerstitial nephritis and lymphadenopathy mimicking IgG4-related disease

We describe a 62-year-old woman with Sjögren's syndrome (SS) presenting with tubulointerstitial nephritis (TIN) and lymphadenopathy mimicking IgG4-related disease (IgG4-RD). Computed tomography revealed multiple swollen lymph nodes. Biopsy of the largest lymph node showed reactive lymphadenopathy with dense IgG4 positive plasma cell (IgG4 + PC) infiltration. Renal biopsy showed chronic plasma cell-rich TIN with IgG4 + PC infiltration. This case suggests that Immunoglobulin G4 immunostaining does not always support the diagnosis of IgG4-RD in the differential diagnosis between SS and IgG4-RD.

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.

Pulmonary nodular lymphoid hyperplasia (pulmonary pseudolymphoma): the significance of increased numbers of IgG4-positive plasma cells

On the basis of an initial case, we hypothesized that IgG4-positive plasma cells may be increased in pulmonary nodular lymphoid hyperplasia (PNLH) compared with other lymphoid proliferations of the lung. Six cases of PNLH, 9 cases of low-grade B-cell lymphoma of the bronchus-associated lymphoid tissue (BALT), 8 cases of intraparenchymal lymph nodes, 8 cases of either primary or secondary follicular bronchiolitis, and 4 cases of lymphocytic interstitial pneumonitis were stained by immunohistochemical analysis for IgG4 and IgG. The mean number of IgG4-positive and IgG-positive plasma cells and the IgG4/IgG ratio were determined from a manual count of images from 3 separate high-power fields (hpf) of areas showing the highest numbers of stained cells, respectively. The mean number of IgG4-positive plasma cells and the IgG4/IgG ratio were significantly increased in PNLH (IgG4=78/hpf, IgG4/IgG=0.35) compared to low-grade lymphoma of BALT (IgG4=4/hpf, P=0.02; IgG4/IgG=0.03, P=0.005), intraparenchymal lymph nodes (IgG4=7/hpf, P=0.03; IgG4/IgG=0.06, P=0.007), follicular bronchiolitis (IgG4=0/hpf, P=0.02; IgG4/IgG=0, P=0.004), and lymphocytic interstitial pneumonitis (IgG4=2/hpf, P=0.02; IgG4/IgG=0.06, P=0.007). These findings support our current understanding of PNLH as a distinct form of reactive lymphoid proliferation, potentially aid in its distinction from low-grade B-cell lymphoma of BALT, and raise the possibility that PNLH may belong within the family of IgG4-related sclerosing diseases.

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.

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.

Increased IgG4-Positive Plasma Cells in Granulomatosis with Polyangiitis: A Diagnostic Pitfall of IgG4-Related Disease

Granulomatosis with polyangiitis (Wegener's) (GPA) may mimic IgG4-related disease (IgG4-RD) on histologic examination of some biopsies, especially those from head and neck sites. IgG4 immunostain is often performed in this context for differential diagnosis with IgG4-RD. However, the prevalence of IgG4+ cells in GPA has not been explored. We examined the IgG4+ cells in 26 cases confirmed as GPA by a thorough clinical and pathologic assessment. Twenty-six biopsies consisted of 14 sinonasal/oral cavity/nasopharynx, 7 orbit/periorbital, 3 lung/pleura, 1 iliac fossa/kidney, and 1 dura specimens. Eight of 26 (31%) biopsies revealed increased IgG4+ cells (>30/HPF and >40% in IgG4+/IgG+ ratio). The IgG4+ cells and IgG4+/IgG+ ratio ranged 37–137/hpf and 44–83%, respectively. Eight biopsies with increased IgG4+ cells were from sinonasal (n = 4) or orbital/periorbital (n = 4) sites. In conclusion, increased IgG4+ cells are not uncommonly seen in sinonasal or orbital/periorbital biopsies of GPA, which could pose as a diagnostic pitfall.

[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.

Clinical and histological changes associated with corticosteroid therapy in IgG4-related tubulointerstitial nephritis

Objectives

This study aimed to investigate the clinicopathological changes induced by corticosteroid therapy in immunoglobulin (Ig)G4-related tubulointerstitial nephritis (TIN).

Methods

We studied six IgG4-related TIN patients receiving renal biopsies before and after corticosteroid therapy. Their clinical data and histological findings were evaluated before and after therapy.

Results

Elevated serum creatinine levels rapidly improved after corticosteroid therapy except for two patients, in whom it persisted. Abnormal radiological findings improved in all patients, although focal cortical atrophy persisted in three. Histologically, TIN-like dense lymphoplasmacytic infiltration, interstitial fibrosis, IgG4-positive plasma cell, CD4+CD25+ T cell, and Foxp3+ cell infiltration were characteristic before therapy. After therapy, the area with cell infiltration decreased and regional fibrosis became evident in the renal interstitium. The number of IgG4-positive plasma cells and Foxp3+ cells significantly diminished even in the early stage of therapy, whereas low to moderate numbers of CD4+ and CD8+ T cells still infiltrated where inflammation persisted in the later stage.

Conclusions

Our study shows that persistent renal insufficiency associated with macroscopic atrophy and microscopic fibrosis is not so rare in IgG4-related TIN. Pathologically, the behavior of regulatory T cells during the clinical course is quite similar to that of IgG4-positive plasma cells, and the behavior pattern of those cells is distinctive.

Light-microscopic characteristics of IgG4-related tubulointerstitial nephritis: distinction from non-IgG4-related tubulointerstitial nephritis

BACKGROUND

IgG4-related disease is a multi-organ disorder characterized by a high level of serum IgG4 and dense infiltration of IgG4-positive cells into affected organs. In routine studies, however, IgG subclasses are not estimated. In the present study, we attempted to clarify the light-microscopic characteristics of IgG4-related tubulointerstitial nephritis (TIN) to facilitate distinction from non-IgG4-related TIN in specimens obtained by renal biopsy using routine staining.

METHODS

In specimens from 34 cases of TIN (13 IgG4-related and 21 non-IgG4-related), 9 nephrologists independently reviewed the following histological features of interstitial lesions: (i) cell infiltration extending into the renal capsule, (ii) cell infiltration into the renal medulla, (iii) regional lesion distribution, (iv) lymphoid follicles, (v) granulomatous lesions, (vi) necrotizing angiitis, (vii) eosinophil infiltration, (viii) neutrophil infiltration, (ix) tubulitis, (x) peritubular capillaritis, (xi) storiform fibrosis and (xii) the stage of interstitial fibrosis. The modified nominal group technique was applied to obtain a consensus in the pathological interpretation.

RESULTS

Consensus was successfully attained among the diagnosticians for all but one pathological feature (regional lesion distribution). Storiform fibrosis was demonstrated in 12 of 13 (92.3%) cases of IgG4-related TIN but in none of the cases of other types of TIN. Cell infiltration extending into the renal capsule was also observed only in IgG4-related TIN. Conversely, neutrophil infiltration, severe tubulitis, severe peritubular capillaritis, granulomatous lesions and necrotizing angiitis were evident only in non-IgG4-related TIN.

CONCLUSIONS

This study revealed some useful and characteristic features for distinguishing IgG4-related from non-IgG4-related TIN on the basis of light-microscopic observation.

Proposal for diagnostic criteria for IgG4-related kidney disease

BACKGROUND

IgG4-related disease has attracted wide attention recently. It is characterized by a high level of serum IgG4 and dense infiltration of IgG4-positive plasma cells into multiple organs, with the kidney being one representative target. Although several sets of diagnostic criteria for autoimmune pancreatitis (AIP) are available and renal lesion is recognized as an extra-pancreatic manifestation of AIP, it is difficult to differentiate IgG4-related tubulointerstitial nephritis (TIN) without AIP from other types of TIN. To clarify the entity of IgG4-related kidney disease (IgG4-RKD) and support in-depth studies, the Japanese Society of Nephrology has established a working group to prepare diagnostic criteria for IgG4-RKD.

METHOD

The working group analyzed 41 patients with IgG4-RKD, and collected the following data to devise a diagnostic algorithm and diagnostic criteria for IgG4-RKD: clinical features including extra-renal organ involvement, urinalysis and serological features including serum IgG4 levels, imaging findings demonstrated by computed tomography (CT), renal histology with IgG4 immunostaining, and response to steroid therapy.

RESULTS

The conditions for criteria are as follows. (1) Presence of some kidney damage, as manifested by abnormal urinalysis or urine marker(s) and/or decreased kidney function with either elevated serum IgG level, hypocomplementemia, or elevated serum IgE level. (2) Kidney imaging studies showing abnormal renal imaging findings, i.e., multiple low density lesions on enhanced CT, diffuse kidney enlargement, hypovascular solitary mass in the kidney, and hypertrophic lesion of the renal pelvic wall without irregularity of the renal pelvic surface. (3) Serum IgG4 level exceeding 135 mg/dl. (4) Renal histology showing two abnormal findings: (a) dense lymphoplasmacytic infiltration with infiltrating IgG4-positive plasma cells >10/high power field (HPF) and/or ratio of IgG4-positive plasma cells/IgG positive plasma cells >40%. (b) Characteristic 'storiform' fibrosis surrounding nests of lymphocytes and/or plasma cells. (5) Extra-renal histology showing dense lymphoplasmacytic infiltration with infiltrating IgG4-positive plasma cells >10/HPF and/or ratio of IgG4-positive plasma cells/IgG-positive plasma cells >40%. The diagnosis is classified into 3 stages of definite, probable and possible according to the combinations of the above conditions. Thirty-nine cases (95.1%) were diagnosed with IgG4-RKD according to the criteria.

CONCLUSION

The provisional criteria and algorithm appear to be useful for clarifying the entity of IgG4-RKD and seeking underlying IgG4-RKD cases; however, further experience is needed to confirm the validity of these criteria.