Value of serum IgG4 in the diagnosis of IgG4-related disease and in differentiation from rheumatic diseases and other diseases

Factors related to elevated serum immunoglobulin G4 (IgG4) levels in a Japanese general population

BACKGROUND

Elevated serum immunoglobulin G4 (IgG4) concentrations are one of the characteristic findings in IgG4-related disease (IgG4-RD). This study investigated the frequency of elevated serum IgG4 levels and associated factors in a general Japanese population.

METHODS

Serum IgG4 concentrations were measured in 1,201 residents of Ishikawa prefecture who underwent general medical examinations. Factors associated with elevated serum IgG4 concentrations were assessed by logistic regression analysis. Participants with elevated serum IgG4 were subjected to secondary examinations.

RESULTS

The mean serum IgG4 concentration was 44 mg/dL, with 42 (3.5%) participants having elevated serum IgG4 levels. Age- and sex-adjusted logistic regression analyses showed that male sex, older age, and lower intake of lipids and polyunsaturated fatty acids and higher intake of carbohydrates in daily diet were associated with elevated serum IgG4 concentration. Subgroup analyses in men showed that older age, lower estimated glomerular filtration rates based on serum cystatin C (eGFR-cysC) levels, and higher hemoglobin A1c (HbA1c) levels were associated with elevated serum IgG4 concentration. Analyses in women showed that lower intake of lipids and fatty acids and higher intake of carbohydrates were significantly associated with elevated serum IgG4 concentration. One of the 15 participants who underwent secondary examinations was diagnosed with possible IgG4-related retroperitoneal fibrosis.

CONCLUSIONS

Elevated serum IgG4 levels in a Japanese general population were significantly associated with older age, male gender, and dietary intake of nutrients, with some of these factors identical to the epidemiological features of IgG4-RD.

Deciphering three predominant biopsy-proven phenotypes of IgG4-associated kidney disease: a retrospective study

Background

IgG4-associated kidney disease (IgG4-RKD) encompasses a spectrum of disorders, predominantly featuring tubulointerstitial nephritis (TIN) and membranous glomerulonephropathy (MGN). The limited understanding of the co-occurrence of IgG4-RD-TIN with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) poses a diagnostic and therapeutic challenge.

Methods

We examined 49 cases, comprising 21 cases of IgG4-RD-TIN (group A), 10 cases of IgG4-RD-TIN accompanied with MGN (group B), and 18 cases of IgG4-RD-TIN concurrent with AAV (group C), at the First Affiliated Hospital of Zhejiang University, China, from June 2015 to December 2022.

Results

The mean age and gender of the three IgG4-RKD subtypes were not statistically significant. IgG4-RD-TIN exhibited higher serum creatinine and a higher incidence of hypocomplementemia (group A 47.6%, group B 30%, group C 16.7%). IgG4-RD-TIN-MGN was characterized by proteinuria (group A 0.3 g/d, group B 4.0 g/d, group C 0.8 g/d, P < 0.001) and hypoalbuminemia. IgG4-RD-TIN-AAV exhibited hypohemoglobinemia (group A 103.45 g/l, group B 119.60 g/l, group C 87.94 g/l, P < 0.001) and a high level of urine erythrocytes. The primary treatment for IgG4-RD-TIN was steroids alone, whereas IgG4-RD-TIN-MGN and IgG4-RD-TIN-AAV necessitated combination therapy. Group A experienced two relapses, whereas groups B and C had no relapses. There was no significant difference in patient survival among the three groups, and only two cases in group C suffered sudden death.

Conclusions

This study provides valuable insights into clinical manifestations, auxiliary examination features, pathological characteristics, and prognosis of IgG4-RD-TIN, IgG4-RD-TIN-MGN, and IgG4-RD-TIN concurrent AAV. Large-scale studies are required to validate these findings.

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

Serum immunoglobulin and the threshold of Fc receptor-mediated immune activation

Antibodies can mediate immune recruitment or clearance of immune complexes through the interaction of their Fc domain with cellular Fc receptors. Clustering of antibodies is a key step in generating sufficient avidity for efficacious receptor recognition. However, Fc receptors may be saturated with prevailing, endogenous serum immunoglobulin and this raises the threshold by which cellular receptors can be productively engaged. Here, we review the factors controlling serum IgG levels in both healthy and disease states, and discuss how the presence of endogenous IgG is encoded into the functional activation thresholds for low- and high-affinity Fc receptors. We discuss the circumstances where antibody engineering can help overcome these physiological limitations of therapeutic antibodies. Finally, we discuss how the pharmacological control of Fc receptor saturation by endogenous IgG is emerging as a feasible mechanism for the enhancement of antibody therapeutics.

Decoding the Clinical Significance of Immunoglobulin G4 in Rheumatoid Arthritis

Immunoglobulin (Ig) G4 accounts for 4-6% of the total IgG in a healthy human. Several evidence-based studies have suggested that the level of IgG4 is significantly elevated in autoimmune diseases, including rheumatoid arthritis (RA). The clinical significance of IgG4 in RA with regard to disease activity, severity, and treatment response remains elusive. We consecutively recruited 174 patients with RA from our rheumatology clinic. All subjects were assessed for their disease activity based on DAS28, radiographic joint damage based on the Modified Sharp Score (MSS), the functional capacity based on the Health Assessment Questionnaire -Disability Index (HAQ-DI), and treatment responsiveness using the European League Against Rheumatism (EULAR) response criteria. The serum IgG4 of the recruited subjects was measured via the ELISA test. The mean serum IgG4 level was 60.23 ± 30.08 mg/dL. We found that serum IgG4 had significant positive correlations with disease activity (r = 0.406; p < 0.001), ESR (r = 0.155; p = 0.041), CRP (r = 0.269; p < 0.001), joint damage (r = 0.195; p = 0.012) and functional disability (r = 0.909; p < 0.001). Subjects with elevated IgG4 (IgG4 > 86 mg/dL) had significantly higher ESR, CRP, HAQ-DI, and DAS 28 and a poorer treatment response compared to the group with non-elevated IgG4. After multivariate analysis, only HAQ-DI (OR = 4.229, 95% CI 1.302, 15.751, p = 0.018) and DAS28 (OR = 3.743, 95% CI 1.062, 13.193, p = 0.040) remained significantly associated with elevated serum IgG4. The preliminary findings of this study could suggest serum IgG4 to be a potential biomarker of disease activity and functional disability in RA.

Can IgG4-related disease present as isolated myositis?

IgG4-Related Disease (IgG4-RD)is a chronic fibroinflammatory disease typically characterized by inflammation or tumefaction of the organs involved. Skeletal muscle is not one of the typical organs involved in IgG4-RD. Isolated myositis related to IgG4-RD without common organ involvement such as lacrimal or salivary glands or retroperitoneal fibrosis is a controversial and debatable entity. Here we report a case of inflammatory myopathy in an elderly woman with several atypical clinical, lab, and histopathological findings suggestive of IgG4-related myositis. Two such case reports of IgG4-related myositis were reported in the literature review. This is a third case report of elevated IgG4 positive plasma cell infiltration in muscle with severe endomysial fibrosis and unusual myositis features (Figs. 1 and 2). This case-based review opens a possibility of a novel presentation of IgG4-RD and new pathogenesis in myositis.

Immunoglobulin G4-related disease with Marked Eosinophilia: A Case Report and Literature Review

We encountered a 78-year-old Japanese man with IgG4-related sialoadenitis complicated with marked eosinophilia. We diagnosed him with IgG4-RD (related disease) with a submandibular gland tumor, serum IgG4 elevation, IgG4-positive plasma cell infiltration, and storiform fibrosis. During follow-up after total incision of the submandibular gland, the peripheral eosinophil count was markedly elevated to 29,480/μL. The differential diagnosis of severe eosinophilia without IgG4-RD was excluded. The patient exhibited a prompt response to corticosteroid therapy. His peripheral blood eosinophil count was the highest ever reported among similar cases. We also review previous cases of IgG4-RD with severe eosinophilia.

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.

The differential diagnosis of IgG4-related disease based on machine learning

INTRODUCTION

To eliminate the disparity and maldistribution of physicians and medical specialty services, the development of diagnostic support for rare diseases using artificial intelligence is being promoted. Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a rare disorder often requiring special knowledge and experience to diagnose. In this study, we investigated the possibility of differential diagnosis of IgG4-RD based on basic patient characteristics and blood test findings using machine learning.

METHODS

Six hundred and two patients with IgG4-RD and 204 patients with non-IgG4-RD that needed to be differentiated who visited the participating institutions were included in the study. Ten percent of the subjects were randomly excluded as a validation sample. Among the remaining cases, 80% were used as training samples, and the remaining 20% were used as test samples. Finally, validation was performed on the validation sample. The analysis was performed using a decision tree and a random forest model. Furthermore, a comparison was made between conditions with and without the serum IgG4 concentration. Accuracy was evaluated using the area under the receiver-operating characteristic (AUROC) curve.

RESULTS

In diagnosing IgG4-RD, the AUROC curve values of the decision tree and the random forest method were 0.906 and 0.974, respectively, when serum IgG4 levels were included in the analysis. Excluding serum IgG4 levels, the AUROC curve value of the analysis by the random forest method was 0.925.

CONCLUSION

Based on machine learning in a multicenter collaboration, with or without serum IgG4 data, basic patient characteristics and blood test findings alone were sufficient to differentiate IgG4-RD from non-IgG4-RD.

Acinar Atrophy, Fibrosis and Fatty Changes Are Significantly More Common than Sjogren’s Syndrome in Minor Salivary Gland Biopsies

Background and Objective: Hyposalivation and xerostomia can result from a variety of conditions. Diagnosis is based on a combination of medical history, clinical and serological parameters, imaging, and minor salivary gland biopsy when indicated. The Objective was to characterize microscopic changes in minor salivary gland biopsies taken in patients with xerostomia. Materials and Methods: 10-year retrospective analysis of minor salivary gland biopsies, 2007–2017. Histomorphometric analysis included gland architecture, fibrosis, fat replacement, inflammation and stains for IgG/IgG4, when relevant. Results: 64 consecutive biopsies, of which 54 had sufficient tissue for diagnosis of Sjogren’s Syndrome (SS) were included (18 males, 46 females, average age 56 (±12.5) years). Only 12 (22.2%) were microscopically consistent with SS, none stained for IgG4. Medical conditions were recorded in 40 (63%), most frequently hypertension and hyperlipidemia (28% each). Medications were used by 45 (70%), of which in 50% more than one. Xerostomia in non-SS cases was supported by abnormal gland morphology, including acinar atrophy, fibrosis and fatty replacement. All morphological abnormalities are correlated with age, while fatty replacement correlated with abnormal lipid metabolism. Multiple medications correlated with microscopic features which did not correspond with SS. Conclusions: SS was confirmed in a minority of cases, while in the majority fatty replacement, fibrosis and multiple medications can explain xerostomia, and are related to aging and medical conditions. Medical history and auxiliary tests could lead to correct diagnosis in non-SS patients, avoiding biopsy. The necessity of a diagnostic biopsy should be given serious consideration only after all other diagnostic modalities have been employed.

Elevated Serum IgG4 Was Found in Eosinophilic Granulomatosis With Polyangiitis

OBJECTIVE

The aim was to determine the levels and clinical impact of immunoglobulin G4 (IgG4) and other IgG subclasses in a Chinese population with eosinophilic granulomatosis with polyangiitis (EGPA).

METHODS

We enrolled 49 patients who had EGPA, 27 who had granulomatosis with polyangiitis (GPA), 31 who had microscopic polyangiitis (MPA), and 30 healthy controls (HCs). Serum IgG subclasses were measured using commercial immunonephelometric assays and compared among different groups.

RESULTS

Fifteen EGPA patients (30.61%) had elevated IgG4 levels, based on a cutoff value of 135 mg/dL. In addition, 2 GPA patients (7.40%) and 1 MPA patient (3.33%) had elevated IgG4 levels. The EPGA group had a higher IgG4 level (65.60 mg/dL) than the GPA group (32.70 mg/dL, p = 0.0021), the MPA group (30 mg/dL, p = 0.0021), and the HC group (28.55 mg/dL, p = 0.0002). The EPGA group also had a higher IgG4/IgG ratio (0.0644) than the GPA group (0.0322, p = 0.13), the MPA group (0.0289, p = 0.0055), and the HC group (0.0212, p < 0.0001).

CONCLUSIONS

Our results indicate that Chinese patients with EGPA have increased levels of serum IgG4. Further study is needed to determine the pathogenic role of IgG4 and IgG4 antineutrophil cytoplasmic antibodies in EGPA.

Immunoglobulin G4-related disease: case report and literature review

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a rare and chronic progressive clinical entity, characterized by elevated serum IgG4 along with tissue infiltration by IgG4 + plasma cells. It is an immune-mediated fibro-inflammatory condition that can affect virtually any organ and tissue. IgG4-related lung disease (IgG4-RLD) occupies 14% of all IgG4-RD, with nonspecific symptoms and various abnormal radiographic patterns. Published data on IgG4-related hypertrophic pachymeningitis (IgG4-RHP), an increasingly recognized central nervous system manifestation of IgG4-RD, is also limited. Both lung and cranial dura involvement have not yet been reported until now. We further entail a review of the literature on the clinicopathologic features and differential diagnosis of this uncommon disease. We herein report an interesting case of a 70-year-old male patient admitted due to headache and fever. A magnetic resonance imaging (MRI) of the brain revealed extensive dural thickening with marked enhancement. Chest computed tomography (CT) scan showed nodular or mass-like consolidation and focal interstitial change. Thoracoscopic lung biopsy and lumbar puncture were conducted. After careful histopathological observation and consideration of alternative differential diagnoses, he was diagnosed with IgG4-related disease with lung and cranial dural involvement based upon significant elevation of serum and cerebrospinal fluid (CSF) IgG4 concentration. The patient was started on oral prednisolone 60 mg/day (1.0 mg/kg/day) for 14 days, and a tapering dose of 5 mg every 2 weeks followed by maintenance therapy at low dose for 3 months. His clinical manifestations, and serologic and imaging findings improved with steroid treatment. Currently, the patient remains well without disease progression. IgG4-RD should be considered as a differential when diagnosing other similar multisystemic lesions. Clinical examination, careful histological observation, and immunostaining for appropriate markers are essential in establishing the diagnosis. Clinicians should become familiar with this alternative differential diagnosis.

IgG4-related disease and idiopathic multicentric Castleman's disease: confusable immune-mediated disorders

IgG4-related disease (IgG4-RD) and idiopathic multicentric Castleman's disease (iMCD) are both rare systemic immune-mediated disorders. However, pathogenesis differs markedly between the two diseases, and differing therapeutic strategies are adopted: IgG4-RD is treated using a moderate dose of glucocorticoids or rituximab, while iMCD therapy involves an interleukin (IL)-6 targeted approach. Nonetheless, some clinical features of IgG4-RD and iMCD overlap, so differential diagnosis is sometimes difficult, even though the classification and diagnostic criteria of the diseases require careful exclusion of the other. The key findings in IgG4-RD are high IgG4/IgG ratio, allergic features, and germinal centre expansion involving T follicular helper cells, while iMCD involves polyclonal antibody production (high IgA and IgM levels), sheet-like mature plasma cell proliferation, and inflammatory features driven by IL-6. The distribution of organ involvement also provides important clues in both diseases. Particular attention should be given to differential diagnosis using combined clinical and/or pathological findings, because single features cannot distinguish IgG4-RD from iMCD. In the present review, we discuss the similarities and differences between IgG4-RD and iMCD, as well as how to distinguish the two diseases.

Renal Involvement in Retroperitoneal Fibrosis: Prevalence, Impact and Management Challenges

Retroperitoneal fibrosis (RPF) is a rare disorder consisting of idiopathic and various secondary forms and characterized by chronic inflammatory infiltrates and marked fibrosis in the retroperitoneal space. In idiopathic RPF (IRPF), 35–60% of cases have been reported to be IgG4-related RPF, the retroperitoneal lesions of IgG4-related disease (IgG4-RD). IRPF can frequently lead to renal insufficiency mediated by urinary tract obstruction and hydronephrosis irrespective of being IgG4-related or not. Clinical pictures, laboratory and imaging findings, and location of the urinary tract obstruction are generally similar in IgG4-related and non-IgG4-related IRPF although multiple organ involvement and serum IgG4 elevation may be characteristic of the IgG4-related forms. Periaortic/periarterial lesions are the most frequent cause of renal insufficiency. Although the response to glucocorticoids is generally good, relapse does occur in a considerable proportion of patients, and may require an additional immunosuppressive agent and/or urological intervention in cases with multiple relapses or refractory obstructive uropathy. In general, the prognosis of patients with IRPF is good, but careful attention needs to be paid to chronic kidney disease as a major complication and rupture of the affected aorta/artery as a life-threatening one. Further studies are necessary to better understand the pathogenesis of the disease and to establish the optimal diagnostic and therapeutic strategies for it.

Imaging of IgG4-related disease in the extracranial head and neck

PURPOSE

Immunoglobulin G4-related disease (IgG4-RD) is a newly defined fibro-inflammatory multisystemic condition defined by a triad of diagnostic criteria based on clinical presentation, biochemical and histopathological findings. Whereas some subsites of this disease have been well described in the literature so far (e.g. pancreas, kidneys, retroperitoneum, salivary glands), more recently identified anatomical sites of involvement in the head and neck are less well understood (e.g. nose, paranasal sinuses).

METHOD

This pictorial review details the imaging appearances of extracranial IgG4-RD in the Head & Neck. Multimodality imaging appearance and features are presented, with reference to the published literature to date.

RESULTS

Following a subsite-based approach, we present both the most common and the more rarely encountered imaging patterns of IgG4-RD in the extracranial head and neck, along with the relevant differential diagnoses to consider. Our institutional experience not only cements what is already known in the existing literature on this topic, but also reveals new imaging features of IgG4-RD, notably in the sinonasal tract.

CONCLUSIONS

This pictorial review of extracranial head & neck IgG4-RD will enable radiologists to recognise the features of this condition and propose it as a differential diagnosis to include alongside other probable entities. It establishes the place of the radiologist in the diagnosis and management of IgG4-RD.

Divergent chemokine receptor expression and the consequence for human IgG4 B cell responses

IgG4 antibodies are unique to humans. IgG4 is associated with tolerance during immunotherapy in allergy, but also with pathology, as in pemphigus vulgaris and IgG4-related disease. Its induction is largely restricted to nonmicrobial antigens, and requires repeated or prolonged antigenic stimulation, for reasons poorly understood. An important aspect in generating high-affinity IgG antibodies is chemokine receptor-mediated migration of B cells into appropriate niches, such as germinal centers. Here, we show that compared to IgG1 B cells, circulating IgG4 B cells express lower levels of CXCR3, CXCR4, CXCR5, CCR6, and CCR7, chemokine receptors involved in GC reactions and generation of long-lived plasma cells. This phenotype was recapitulated by in vitro priming of naive B cells with an IgG4-inducing combination of T_FH /T_H2 cytokines. Consistent with these observations, we found a low abundance of IgG4 B cells in secondary lymphoid tissues in vivo, and the IgG4 antibody response is substantially more short-lived compared to other IgG subclasses in patient groups undergoing CD20⁺ B cell depletion therapy with rituximab. These results prompt the hypothesis that factors needed to form IgG4 B cells restrain at the same time the induction of a robust migratory phenotype that could support a long-lived IgG4 antibody response.

Eosinophilic pancreatitis versus pancreatitis associated with eosinophilic gastroenteritis - a systematic review regarding clinical features and diagnosis

BACKGROUND

Over the past years, eosinophil infiltration involving the gastrointestinal tract and pancreas leading to eosinophilic pancreatitis, eosinophilic gastroenteritis and hypereosinophilic syndrome has been reported in the literature. We aimed to analyze and compare the features involving patients with eosinophilic pancreatitis and pancreatitis associated with eosinophilic gastroenteritis and to determine if there is a connection between the two disorders or if they in fact meet the diagnostic criteria for hypereosinophilic syndrome.

MATERIAL AND METHODS

The following search was performed in March 2019 on PubMed (MEDLINE) database using the medical terms "pancreatitis", "eosinophilic pancreatitis", "eosinophilic gastroenteritis" and "hypereosinophilic syndrome".

RESULTS

The search revealed 119 publications from 1970 onwards. A total of 83 papers were excluded, and the remaining 36 publications, consisting in case reports and case series, were analyzed. From 45 patients, 20 subjects with eosinophilic gastroenteritis developed pancreatitis, 20/45 had eosinophilic pancreatitis, and 5/45 hypereosinophilic syndrome involving the pancreas. There was no significant difference regarding clinical, laboratory and imaging features between the three groups, despite the multiple theories that explain the association of pancreatic and gastrointestinal eosinophilic infiltration. Although there was a strong resemblance between the three groups, histological evidence of eosinophilic gastrointestinal infiltration guided the treatment towards a less invasive way, while subjects with eosinophilic pancreatitis underwent pancreatic surgery to exclude potentially malignant lesions.

CONCLUSION

Although there are various theories that explain pancreatitis development in patients with eosinophilic gastroenteritis, hypereosinophilia diagnostic work-up should be taken into account in all patients with high number of blood eosinophils, even in those with eosinophilic pancreatitis in order to establish the diagnosis using a minimally invasive approach and to apply an adequate treatment.

Immunoglobulin G4-related Disease

Immunoglobulin G4 (IgG4)-Related Disease (IgG4-RD) can cause fibroinflammatory lesions in nearly any organ and lead to organ dysfunction and irreversible damage. In addition to frequent involvement of the salivary glands, lacrimal glands, and/or pancreas, IgG4-RD often affects the chest. Thoracic manifestations include lung nodules and consolidations, pleural thickening, aortitis, and lymphadenopathy. The diagnosis is made after careful clinicopathologic correlation because there is no single diagnostic test with excellent sensitivity or specificity. Biopsy of pulmonary lesions can be useful for distinguishing IgG4-RD from common mimickers. Immunosuppressive regimens, such as glucocorticoids and/or glucocorticoid-sparing agents, form the cornerstone of treatment.

Interstitial pneumonia with autoimmune features that met the proposed diagnostic criteria for IgG4-related respiratory disease

We held a multidisciplinary discussion (MDD) about a 61-year-old woman who had an interstitial lung disease (ILD) without extrathoracic lesions that met the classification criteria for interstitial pneumonia with autoimmune features (IPAF) and the proposed diagnostic criteria for immunoglobulin G4 (IgG4)-related respiratory disease (IgG4-RRD). Clinically, the marked progression of lung-limited diffuse lesions was consistent with IPAF. Serum IgG4 and rheumatoid factor levels simultaneously increased and did not contribute to a diagnosis. Pathologically, the significant hyperplasia of lymphoid follicles was consistent with rheumatoid arthritis (RA)-associated ILD. Pulmonary venous occlusions by intimal fibrosis and intimal thickening were not important because these occlusions are found in IgG4-related lung disease (IgG4-RLD) and also in IPAF or ILDs related to connective tissue diseases (CTDs). Radiologically, fibrosing shadows that remained in the lung periphery after treatment were compatible with RA-associated chronic ILD. We concluded that the present case was IPAF that met the proposed diagnostic criteria for IgG4-RRD.

IgG4-type Multiple Myeloma with Diffuse Enlargement of the Thyroid Requiring Differentiation from IgG4-related Disease

We herein report a 65-year-old man with elevated serum IgG4 levels, enlarged thyroid, and renal dysfunction, mimicking IgG4-related disease (IgG4-RD). The definitive diagnosis of IgG4-RD was not established because a tissue biopsy revealed no IgG4-positive cell infiltration or fibrosis. The presence of an M peak in the β fraction, Bence Jones protein in urine, and progressive anemia suggested multiple myeloma (MM). The κ/λ ratio was >100, tumor plasma cells were present at >20% in bone marrow, and immunostaining revealed IgG4-positive plasma cells; therefore, he was diagnosed with IgG4-type MM. Patients with elevated IgG4 levels with no significant mass lesions should undergo systemic examinations to exclude malignancy.

Review of IgG4-related disease

IgG4-related disease is a fibrous-inflammatory process related to immunomodulation. The most commonly affected organs are: the pancreas, bile duct, major salivary glands, lacrimal glands, retroperitoneum and lymphatic ducts. In recent decades, this disease has been recognised as a systemic disorder that includes many single organ disorders, previously unrelated and known as independent entities. The common characteristics shared by the different entities that make up the IgG4-related disease are: raised serum IgG4 levels, alterations in the imaging tests with neoplastic-like swelling of the affected organs, specific histopathological characteristics and in immunostaining, as well as good response to treatment with glucocorticoids. In this work, we will review this pathology with a special emphasis on the characteristics of autoimmune pancreatitis, sclerosing cholangitis related to IgG4 and the involvement of the retroperitoneum, mesenterium and the digestive tract.

Distribution characteristics of elevated serum immunoglobulin G4 (IgG4) and its relationship with IgG4-related disease

Objective: To elucidate the distribution characteristics of elevated serum immunoglobulin G₄ (IgG₄) and its relationship with immunoglobulin G₄-related disease (IgG₄-RD).Methods: In total, 14 522 unique patients who were tested for serum IgG₄ over a 4.5 year period were enrolled. Demographic and serological characteristics of all patients, and the range of diseases and serological characteristics of patients with elevated serum IgG₄, were retrospectively analysed. Organ involvement in IgG₄-RD patients and the utility of serum immunoglobulin for distinguishing IgG₄-RD from non-IgG₄-RD were also investigated.Results: Elevated serum IgG₄ (> 1.4 g/L) was observed in 1793/14 522 patients (12.3%) and primarily appeared in middle-aged and elderly men. Only 7.3% of patients with elevated serum IgG₄ met the diagnostic criteria for IgG₄-RD. Elevated serum IgG₄ was also found in over 30 types of non-IgG₄-RD. Serum IgG₄ levels were higher in IgG₄-RD patients with multiple-organ involvement and were positively correlated with the number of affected organs. The diagnostic utility of serum IgG₄ for IgG₄-RD was higher than that of the IgG₄/IgG ratio and serum IgG. The optimal serum IgG₄ cut-off value for diagnosing IgG₄-RD was 2.06 g/L, with a sensitivity of 95.6% and specificity of 94.7%.Conclusions: Elevated serum IgG₄ may be present in multiple non-IgG₄-RD conditions. However, a high serum IgG₄ concentration is of great value for IgG₄-RD diagnosis, and there appears to be a positive relationship between serum IgG₄ levels and organ involvement in patients with IgG₄-RD. Examining the IgG₄/IgG ratio and serum IgG does not improve the ability of IgG₄-RD diagnosis.

IgG4-aortitis among thoracic aortic aneurysms

Objective

The incidence of aortitis in patients with thoracic aortic diseases is not well established. The aim of this study was to analyse the frequency and clinical course of patients with aortitis in a surgical series.

Methods

320 consecutive patients with ascending aorta/aortic arch aneurysm or acute aortic syndrome who underwent surgery from 2012 to 2017 in a single tertiary referral hospital were retrospectively reviewed. Epidemiological data, clinical course and variables related to diagnosis, treatment and follow-up were collected from patients with histologically proven aortitis.

Results

From 320 examined aortic samples, 279 (87.2%) thoracic aneurysms and 41 acute aortic syndromes (12.8%), 9 (2.8%) were aortitis: 3 cases of Takayasu’s arteritis, 3 of IgG4-related aortitis, 2 of giant cell, and 1 classified as idiopathic. Median age at surgery was 53.4 (51–69.2) years and six cases were female. Seven patients presented with non-specific symptoms and the diagnosis was made at pathology. Surgery was elective in eight patients and emergent in one case of IgG4-related aortitis. 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG PET/CT) was performed for disease extension study and as a monitoring technique during the follow-up of five patients, with just one case performed presurgically. All the patients with IgG4-related disease showed extrathoracic aortic involvement. There were no deaths, neither in-hospital nor during the 1.7 years of median follow-up.

Conclusions

In surgically treated thoracic aorta pathology, the frequency of aortitis is low; IgG4-related disease is among the most common aetiologies with a frequency similar to other types of aortitis, such as Takayasu’s and giant cell arteritis, and clinical manifestations are non-specific making presurgical diagnosis difficult. 18F-FDG PET/CT allows a better assessment of disease extension and therapeutic response. Surgery can be successfully performed and corticosteroid therapy ensures a good mid-term follow-up.

IgG4-related respiratory disease

IgG4-related diseases (IgG4-RDs), such as autoimmune pancreatitis and IgG4-related Mikulicz disease, are often accompanied by intrathoracic lesions, which are called IgG4-related respiratory disease (IgG4-RRD). IgG4-RRD has few subjective symptoms, and is usually detected during workup of patients with extra-thoracic lesions of IgG4-RD. IgG4-RRD is characterized by various conditions, including masses, nodules, thickening, and infiltration at numerous sites in the thorax through lymphatic routes. Although elevated serum IgG4 concentrations and pathologic evidence of lymphoplasmacytic infiltrates with abundant IgG4-positive plasma cells are characteristic findings of IgG4-RD, other intrathoracic diseases, such as multicentric Castleman disease and malignancy, may present with similar findings. Developing diagnostic criteria for IgG4-RRD, including clinicoradiological and pathological characteristics, is necessary for its appropriate diagnosis.

Head and neck immunoglobulin G4 related disease: systematic review

BACKGROUND

Immunoglobulin G4 related disease is a recently described systemic syndrome. The head and neck region is the second most common site for presentation after the pancreas.

METHODS

PubMed and the Cochrane Library were searched from 1995 to July 2017 for all the studies on immunoglobulin G4 related disease diagnosed in the head and neck compartment. Patient-specific data were extracted and basic statistical analysis was performed.

RESULTS

Ninety-one patients were identified. Treatment was specified in 76 patients. Twenty patients received surgical treatment, eight of them in association with medical therapy. Fifty-six patients received medical treatment. The disease recurred in 25 per cent of patients treated with surgical treatment alone, in 3.6 per cent of patients treated with medical treatment alone and in 12.5 per cent of patients treated with both. All medical treatment protocols contained high-dose corticosteroids.

CONCLUSION

Early and correct diagnosis can avoid unnecessary surgical treatment, and glucocorticoid therapy can improve the long-term prognosis.

IgG4-related Pleuritis with Elevated Adenosine Deaminase in Pleural Effusion

An 81-year-old man was admitted with bilateral pleural effusion. A clinical examination showed lymphocytic pleura effusion and elevated serum IgG4 levels, so that IgG4-related disease was suggested, whereas tuberculous pleurisy was suspected because of high adenosine deaminase (ADA) levels in the pleural effusion. A surgical pleural biopsy revealed that there were large numbers of IgG4-positive cells and IgG4/IgG positive cell ratio exceeded 40% in several sites. Accordingly, we diagnosed IgG4-related pleuritis and treated with the patient with glucocorticoid therapy. The ADA levels in pleural effusion can increase in IgG4-related pleuritis, and it is therefore important to perform a pleural biopsy.

IgG4-related retroperitoneal fibrosis overlapping with primary biliary cirrhosis and primary Sjögren's syndrome: A case report

RATIONALE

IgG4-related disease (IgG4-RD) is a chronic fibro-inflammatory disorder which is characterized by elevated levels of serum IgG4 and infiltration of IgG4-bearing plasma cells in the involved organs. Primary biliary cirrhosis (PBC) and Primary Sjögren's syndrome (pSS) are both distinct from IgG4-related disease. We herein describe a Chinese patient with IgG4-related RPF overlapping with PBC and pSS.

PATIENT CONCERNS

We report a case of 69-year-old male with recurrent lower abdominal pain for 10 months. Laboratory data showed elevated erythrocyte sedimentation rate and hepatobiliary enzymes, renal dysfunction, high titers of antinuclear antibody, anti-SS-A antibody and anti-mitochondrial type 2, high immunoglobulin (Ig) G levels and elevated serum IgG4 (9 g/L). Contrast-enhanced computed tomography and magnetic resonance imaging were suggestive of retroperitoneal fibrosis and unilateral ureteral occlusion. Immunohistochemical staining for IgG4 did not demonstrate infiltration of IgG4-positive plasma cells in the retroperitoneal mass, but revealed significant infiltration of lymphocytoplasma cells as well as fibrosis and fibrin accumulation.

DIAGNOSES

The patient was diagnosed with IgG4-related retroperitoneal fibrosis based on the International Consensus Diagnostic Criteria. He was also diagnosed with primary biliary cirrhosis and primary Sjögren's syndrome.

INTERVENTIONS

250 mg ursodeoxycholic acid was administered twice daily, and prednisolone was initiated at a dose of 40 mg/day and then tapered to 25 mg after 45 days.

OUTCOMES

The size of the retroperitoneal soft tissue mass gradually reduced and the abnormal laboratory parameters were restored to normal.

LESSONS

This rare clinical condition has seldom been reported in the literature, which suggests that common immunogenetic factors may be involved in the development of IgG-related RPF, PBC and pSS.

Polymyositis with elevated serum IgG4 levels and abundant IgG4+ plasma cell infiltration: A case report and literature review

INTRODUCTION

Polymyositis (PM) is a type of autoimmune, inflammatory myopathy. IgG4-related disease (IgG4-RD) is a recently recognized disease entity characterized by elevated serum IgG4 levels and IgG4 plasma-cell infiltration of various organs. However, several reports have described cases of other diseases that present with those features, suggesting the importance of careful differential diagnosis. Herein, we report the first case of PM with elevated serum IgG4 levels and IgG4 plasma cells in the muscles, mimicking IgG4-RD.A 73-year-old woman visited our hospital because of proximal muscle weakness of both thighs. Her blood test showed high levels of serum creatinine kinase, aldolase, and IgG4. Magnetic resonance imaging of the thighs showed muscle edema. Needle electromyography showed findings typical of myositis. Histological analysis of her left quadriceps revealed infiltration of IgG4 plasma cells as well as CD8 T cells. Scattered necrotic and regenerating muscle fibers with no specific findings for IgG4-RD (storiform fibrosis and obliterative phlebitis) were typical for PM. We diagnosed her condition as PM and treated her with 40 mg/day of prednisolone that decreased levels of muscle enzymes and improved muscle weakness.

CONCLUSION

Our case indicated that PM could present with high serum IgG4 levels and IgG4 plasma-cell infiltration, mimicking IgG4-RD. Although the mechanism of IgG4 elevation in such PM is unclear, our case highlights the necessity to recognize that high serum IgG4 levels and IgG4 plasma-cell infiltration in organs are not specific for IgG4-RD.

Utility of Serum IgG4 Levels in a Multiethnic Population

BACKGROUND

IgG4-related disease (IgG4-RD) is a recently recognized condition defined by characteristic histopathologic findings in affected organs. Serum IgG4 concentration is often but not always elevated. The sensitivity and specificity of serum IgG4 vary greatly across studies and has been anecdotally associated to ethnicity. Our study was conducted to investigate the difference in serum IgG4 levels between Asian and non-Asian patients with IgG4-RD.

METHODS

This is a single-center retrospective study of 26 Asian and 10 non-Asian patients with histologically confirmed IgG4-RD. Serum IgG4 levels, clinical features and other laboratory findings were compared between the 2 groups, 31 Asian and 11 non-Asian patients with non-IgG4-RD rheumatic diseases were randomly identified to evaluate test characteristics of serum IgG4 measurement.

RESULTS

Median serum IgG4 at time of diagnosis was significantly higher in Asian (median = 11.2g/L, interquartile range: 4.6-19.7) than non-Asian patients (median = 2.9g/L, interquartile range: 0.7-5.4, P = 0.0094), as well as the median serum IgG and total protein. Asian patients had more eosinophilia and polyclonal hypergammaglobulinemia than non-Asian patients (P = 0.016 and 0.001, respectively). Test sensitivity was higher in Asian (96%) than non-Asian patients (67%), whereas test specificity was higher in non-Asian patients (91% versus 71%).

CONCLUSION

Asian patients with IgG4-RD have more exuberant serum IgG4, IgG and polyclonal hypergammaglobulinemia than non-Asian patients; the mechanism of this difference requires further study. These findings have significant clinical importance and must be accounted for in the diagnostic workup of patients in multiethnic settings.

Distinct features distinguishing IgG4-related disease from multicentric Castleman's disease

Objectives

Differentiating IgG4-related disease (IgG4-RD) from multicentric Castleman’s disease (MCD) is challenging because both diseases present high serum IgG4. The objective of this study is to clarify the differences in characteristics and identify a clinically useful approach to differentiate these two diseases.

Methods

Forty-five consecutive patients with untreated active IgG4-RD and 33 patients with MCD were included in this study, who visited our institution from January 2000 to August 2016. The clinical and laboratory findings for the patients of the two diseases were compared. Various combinations of the distinctive findings were evaluated to identify the most efficient differentiating features between IgG4-RD and MCD.

Results

The levels of serum IgG4 were not different between the two diseases. Orbits, lacrimal glands, salivary glands or pancreas were involved in 88.9% of IgG4-RD cases and only in 3.0% of MCD cases. All MCD cases involved lymph nodes. Atopic history was characteristic for IgG4-RD. The levels of C reactive protein (CRP) with a cut-off of 0.80 mg/dL and IgA with a cut-off of 330 mg/dL were the most distinctive. The combination of ‘Orbits, lacrimal glands, salivary glands or pancreas involvement, atopic history, or non-involvement of lymph node’ and ‘CRP ≤ 0.8 mg/dL or IgA ≤ 330 mg/dL’ yielded the probability of 97.8% in IgG4-RD, while that of 3.0 % in patients with MCD.

Conclusions

Our study revealed distinct features between IgG4-RD and MCD. Differentiating between the diseases based on those distinct features, including distribution of organ involvement, atopic history, levels of IgA and CRP, was a useful approach.

Surgical management of isolated mesenteric autoimmune disease: addressing the spectrum of IgG4-related disease and sclerosing mesenteritis

IgG₄-related disease (IgG₄-RD) is a rare form of autoimmune sclerosing disease, characterised by elevated serum IgG₄ and tissue IgG₄ levels, specific histopathological findings, multiorgan involvement and adequate response to glucocorticoid treatment. The low incidence and the heterogeneous nature of the disease has made consensus on diagnostic criteria for IgG₄-RD difficult. Whether sclerosing mesenteritis (SM) is considered a manifestation of IgG₄-RD is strongly debated. We present the case of a patient with a history of rheumatoid arthritis who presented with a calcified abdominal mass. She was found to have an isolated, pedunculated mesenteric mass positive for IgG₄ and concurrently elevated serum IgG₄ levels. Clinical features did not classify her disease as either SM or IgG₄-RD as currently described in consensus statements. Concurrent diagnoses of IgG₄-RD, SM and other autoimmune disorders, as well as postoperative recommendations for resected isolated IgG₄-positive masses, are discussed.

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome with remarkably elevated serum IgG4

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare inflammatory disorder with unknown etiology, while the evidence of the association between IgG4 and inflammatory disorders is accumulating. We present the first report of a patient with SAPHO syndrome with remarkably elevated serum IgG4. The clinical features of this 45-year-old male patient included pain of the anterior chest wall and right elbow, bone marrow edema in the ulna suggested by magnetic resonance imaging (MRI), the “bull’s head” sign on the bone scintigraphy, and remarkably increased IgG4 and interleukin-6. This report may indicate a spectrum of diseases with serum IgG4 elevation broader than previously reported. Moreover, it also provides information on the underlying abnormal immune response in SAPHO syndrome.

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.

Recent advances in knowledge regarding the head and neck manifestations of IgG4-related disease

IgG4-related disease (IgG4-RD) is a chronic inflammatory disorder, characterized by elevated serum IgG4 levels as well as abundant infiltration of IgG4-positive plasmacytes and fibrosis in various organs, including the head and neck region. In particular, the salivary glands, orbit, and thyroid are common sites of disease involvement. IgG4-RD is diagnosed based on various clinical, serological, and histopathological findings, none of which are pathognomonic. Hence, various differential diagnoses, which exhibit elevated serum IgG4 levels and infiltration of IgG4-postive cells into tissues, need to be excluded, especially malignant diseases and mimicking disorders. Systemic corticosteroids are generally effective in inducing IgG4-RD remission; however, recurrent or refractory cases are common. In addition, although the pathogenic mechanisms of IgG4-RD remain unclear, an antigen-driven inflammatory condition is believed to be involved. Recent studies have indicated the important pathogenic role of B cell/T cell collaboration and innate immunity in this disease. Nevertheless, additional research and discussions are needed to resolve many remaining questions. In this review, we provide an overview of the recent insights on the history, clinical features, diagnosis, and treatment of IgG4-RD in the head and neck region. Furthermore, we have also addressed the pathogenesis of this disease.

Gallium SPECT/CT in evaluation of IgG4-related disease: A case report and literature review

BACKGROUND

The clinical picture of IgG4-related sclerosing disease (IgG4-RSD) may mimic lymphoma, and should be in the differential diagnosis of patients with this clinical picture.

CASE SUMMARY

A 32-year-old female had recurrent swelling of both eyelids for more than 15 years. Examination revealed elastic, firm, swollen lacrimal glands about 2-3 cm in diameter that was not painful. Head and orbits magnetic resonance imaging (MRI) showed mass lesions over the bilateral lacrimal glands, submandibular glands, and left foramen of ovale. The differential diagnosis included lymphoid tissue, inflammatory masses, and lymphoma. Gallium single-photon emission computed tomography/computed tomography (SPECT/CT) showed uptake in the bilateral lacrimal glands, right parotid and bilateral submandibular glands, bilateral perirenal region, mediastinal, prevertebral, paraaortic, lumbar, bilateral pelvic (including internal iliac chain) lymph nodes, anterior aspect of right 3rd rib, and lateral aspect of left 6th rib. CT showed multiple enlarged lymph nodes in the mediastinum, right pulmonary hilum, prevertebral space of the thoracolumbar spine, retroperitoneal paraaortic area, bilateral parailiac areas, and bilateral perirenal spaces. Antinuclear and anti-SSA/SSB antibodies were negative, and the serum IgG4 level was 740 mg/dL (normal, 8-140 mg/dL). Right parotid gland biopsy showed abundant IgG4-positive plasma cells. Mikulicz disease (IgG4-related sclerosing disease) was diagnosed and she received glucocorticoid treatment. Follow-up CT and MRI showed with resolved eyelid swelling and perirenal mass lesions. Follow-up gallium scan was normal.

CONCLUSION

Gallium SPECT/CT can be a useful tool for initial and follow-up evaluation of IgG4-RSD.

Diagnostic Value of Serum IgG4 for IgG4-Related Disease: A PRISMA-compliant Systematic Review and Meta-analysis

Many studies about serum IgG4 for the diagnosis of IgG4-related disease (IgG4-RD) have been reported. However, these studies had relatively small sample sizes and the diagnostic accuracy values varied much between them.The aim of this study was to perform a meta-analysis to evaluate the diagnostic value of serum IgG4 for IgG4-RD.We conducted a search of relevant articles using MEDLINE, EMBASE, Web of Science, SCOPUS, and Cochrane Library databases published before December 2015.Studies those assessed the diagnostic accuracy of serum IgG4 for IgG4-RD and those provided the cut-off value for serum IgG4 were included.Data were synthesized using the random-effect model. Statistical analysis was performed using STATA with the MIDAS module and Meta-DiSc 1.4 software.A total of 9 case-control studies were analyzed, which included 1235 patients with IgG4-RD and 5696 overall controls. The pooled estimate, for a cut-off value ranged from 135 to 144 mg/dL, produced a sensitivity of 87.2% (95% CI, 85.2-89.0%) and a specificity of 82.6% (95% CI, 81.6-83.6%). The positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were 6.48 (95% CI, 3.98-10.57), 0.14 (95% CI, 0.09-0.21), and 45.15 (95% CI, 23.41-87.06), respectively. The area under the curve (AUC) of the summary receiver operating characteristic curve (SROC) was 0.94 (0.92-0.96). When a cut-off value of 2-fold the upper limit of normal was used (ranged from 270 to 280 mg/dL), the pooled sensitivity was 63% (95% CI, 60.0-66.0%), and the specificity was 94.8% (95% CI, 94.1-95.4%). The PLR, NLR, and DOR were 13.3 (95% CI, 7.39-24.0), 0.41 (95% CI, 0.29-0.58) and 33.42 (95% CI, 13.88-80.43), respectively. The AUC of the SROC was 0.92 (0.90-0.94).Only a relatively small number of studies were included, and significant heterogeneity was observed in this meta-analysis.Serum IgG4 is a modestly effective marker to diagnose IgG4-RD. Doubling the cut-off value for IgG4 could not improve the overall test characteristics. A high specificity inevitably accompanies with a significant sacrifice in sensitivity.

Kidney involvement in medium- and large-vessel vasculitis

Medium- and large-vessel vasculitides (MVV and LVV, respectively) comprise a heterogeneous group of disorders whose common denominator is the inflammatory involvement of vessels of medium and large size. This disease spectrum includes giant-cell arteritis and Takayasu's arteritis, which typically affect the aorta and its main branches, and Kawasaki's disease and polyarteritis nodosa, which involve medium-sized arteries. Chronic periaortitis, characterized by a perivascular fibro-inflammatory reaction affecting the abdominal aorta and the periaortic tissue, frequently has a systemic distribution, involving other segments of the aorta and its major branches, and could thus be included in this group. Unlike small-vessel vasculitides, MVV and LVV do not cause glomerulonephritis, although glomerular immune-mediated lesions and tubulo-interstitial nephritis occur with varying frequency. However, MVV and LVV can often involve the renal artery and its branches, causing a wide array of lesions that range from renal artery stenosis to intra-renal vasculitis causing renal ischaemia/infarction, microaneurysms and haemorrhage. This review focuses on renal involvement in MVV and LVV and underlines why renal abnormalities in these syndromes should not be overlooked.