Mass spectrometry in IgG4-related disease diagnosis

We compared liquid chromatography tandem mass spectrometry (LC-MS/MS) against Binding Site immunonephelometry (BSIN) with regards to these methods' abilities to diagnose IgG4-related disease (IgG4-RD). IgG subclasses were gathered from laboratory from December 2011 to December 2020. The IgG4-RD positive and negative patients were diagnosed according to the ACR/EULAR classification criteria by extensive chart review. Both methods' results were compared in terms of test characteristics. For BSIN, there were 43 IgG4-RD positive cases and 174 disease negative cases, while for LC-MS/MS, there were 102 IgG4-RD positive cases and 562 disease negative cases. The majority of IgG4-RD patients by BSIN and LC-MS/MS had an elevated IgG4 level, 81% and 86%, respectively. For BSIN, the ROC curve, cut-off value of 1.25 g/L, had a sensitivity of 81% and a specificity of 84%. For LC-MS/MS, the ROC curve, cut-off value of 1.25 g/L, had a sensitivity of 86% and a specificity of 84%. The responder index score to IgG4 level r-correlation value for BSIN and LC-MS/MS was 0.5 and 0.6, respectively. In our center, LC-MS/MS and BSIN are equivalent test methods in IgG4-RD diagnosis. IgG4 level does correlate with disease activity by the responder index. LC-MS/MS is a valid and equally reliable alternative to BSIN in the diagnosis of IgG4-related disease.

IgG4-related digestive diseases: diagnosis and treatment

IgG4-related digestive diseases encompass a group of chronic inflammatory disorders characterized by autoimmune reactions and fibrosis affecting multiple digestive organs. These diseases are identified by elevated serum levels of IgG4 and the presence of IgG4-positive plasma cell infiltration in the affected sites, along with storiform fibrosis, obliterative phlebitis, and eosinophilic infiltration. Although extensive research has been conducted, a comprehensive understanding of these conditions remains elusive. Current clinical diagnosis often relies on the application of integrated diagnostic criteria for IgG4-related diseases, combined with specific organ involvement criteria. Distinguishing them from malignancies poses considerable challenges. Moreover, further investigations are required to elucidate the underlying pathogenic mechanisms and explore potential therapeutic interventions. This review provides a systematic classification of IgG4-related digestive diseases while discussing their diagnostic strategies, clinical presentations, and treatment modalities. The comprehensive insights shared herein aim to guide clinicians in their practice and contribute to the advancement of knowledge in this field.

Misdiagnosis and delayed diagnosis of atypical autoimmune pancreatitis: Experience from clinical cases

Autoimmune pancreatitis (AIP) is a fibro-inflammatory disease characterized by inflammation and fibrosis of the pancreas. It is a systemic disease that can affect multiple organs, including the bile ducts, kidneys, lungs, and other organs. However, due to its complex presentation, AIP is often challenging to diagnose, and misdiagnosis with pancreatic tumors can occur. In our study, we reviewed three cases of atypical AIP where patients had normal serum IgG4 levels, leading to initial misdiagnosis with pancreatic tumors. Delayed diagnosis resulted in irreversible pathologies such as retroperitoneal fibrosis. All three patients had bile duct involvement, and imaging findings were similar to those of tumors, further complicating the diagnosis. The correct diagnosis was confirmed only after diagnostic therapy. Our study aims to raise awareness of atypical AIP and improve diagnostic efficiency by analyzing the clinical characteristics of these patients.

Case report: Clinical highlights and radiological classification of IgG4-related spinal pachymeningitis: A rare case series and updated review of the literature

Purpose

Hypertrophic pachymeningitis associated with immunoglobulin G4-related disease (IgG4-RD) has been rarely reported, and there is little information and no clear consensus on the management of IgG4-related spinal pachymeningitis (IgG4-RSP). The present study described its possible clinical features, including the symptoms, imaging, treatment and prognosis of patients with IgG4-RSP.

Methods

We report three patients who presented with progressive neurological dysfunction due to spinal cord compression. Relevant articles were searched from the PubMed, Web of Science, and Embase databases, and the resulting literature was reviewed.

Results

The literature review provided a summary of 45 available cases, which included three cases from our center. Progressive worsening of neurological impairment was observed in 22 patients (48.9%). The lesions involved the thoracic spine (n=28, 62.2%), cervical spine (n=26, 57.8%), lumbar spine (n=9, 20.0%), and sacral spine (n=1, 2.2%). Furthermore, the lesions were located in the dura mater (n=18, 40.0%), epidural space (n=17, 37.8%), intradural-extramedullary space (n=9, 20.0%), and intramedullary space (n=1, 2.2%). On magnetic resonance imaging (MRI), the lesions generally appeared as striated, fusiform, or less often lobulated oval changes, with homogeneous (n=17,44.7%) and dorsal (n=15,39.5%) patterns being the most common. Thirty-five patients had homogeneous T1 gadolinium enhancement. Early surgical decompression, corticosteroid treatment, and steroid-sparing agents offered significant therapeutic advantages. A good therapeutic response to disease recurrence was observed with the medication.

Conclusion

The number of reported cases of IgG4-RSP remains limited, and patients often have progressive worsening of their neurological symptoms. The features of masses identified on the MRI should be considered. The prognosis was better with decompression surgery combined with immunosuppressive therapy. Long-term corticosteroid treatment and steroid-sparing agent maintenance therapy should be ensured. A systemic examination is recommended to identify the presence of other pathologies.

Correlation between serologic parameters and disease activity of IgG4-related disease: Differences between patients with normal and elevated serum IgG4 concentrations

Objective

We aimed to identify serologic parameters that correlate with the disease activity of IgG4-related disease (IgG4-RD) in patients with normal and elevated serum IgG4 concentrations, respectively.

Methods

This retrospective cohort study included 148 patients with IgG4-RD. Patients were categorized into normal (≤201 mg/dL) and elevated (>201 mg/dL) serum IgG4 concentration groups. Disease activity was assessed using the IgG4-RD responder index (RI). The correlations between IgG4-RD RI and serologic parameters (erythrocyte sedimentation rate [ESR], C-reactive protein, C3, C4, IgG4 concentration, IgG concentration, and IgG4/IgG ratio) were evaluated in each group, using Spearman’s correlation coefficient.

Results

Of the 148 patients with IgG4-RD, 38 (25.7%) and 110 (74.3%) patients were categorized into the normal and elevated serum IgG4 concentration groups, respectively. In the normal serum IgG4 concentration group, IgG concentration was the only serologic parameter that showed a significant correlation with IgG4-RD RI (rho=0.411, p=0.013). However, in the elevated serum IgG4 concentration group, ESR (rho=0.196, p=0.041), C3 (rho=-0.432, p<0.001), C4 (rho=-0.363, p=0.001), IgG4 concentration (rho=0.423, p<0.001), IgG concentration (rho=0.224, p=0.020), and IgG4/IgG ratio (rho=0.328, p=0.001) correlated with IgG4-RD RI. The combination of C3 and IgG4 concentration (rho=0.509, p<0.001) had the strongest correlation with IgG4-RD RI in this group.

Conclusion

Among the serologic parameters tested, IgG concentration was the only parameter that correlated with IgG4-RD RI in patients with normal serum IgG4 concentrations, whereas multiple parameters correlated with IgG4-RD RI in those with elevated serum IgG4 concentrations. The combination of C3 and IgG4 concentration had the strongest correlation coefficient in the latter group.

The role of serological biomarkers in the diagnosis and management of autoimmune pancreatitis

INTRODUCTION

Autoimmune pancreatitis (AIP) is a fibroinflammatory disease of the pancreas. Type 1 AIP is the pancreatic manifestation of a systemic IgG4-related disease and is associated with serum elevation of IgG4, tissue infiltration of IgG4-positive plasma cells, and multiorgan involvement. Although serum IgG4 elevation is considered a useful diagnostic tool, the concomitant presence of more diagnostic criteria is needed to achieve diagnosis. No other biomarkers have been approved in clinical practice in type 1 AIP. Type 2 AIP is a pancreatic-specific disease associated with inflammatory bowel disease. No specific biomarkers for type 2 AIP have been identified.

AREAS COVERED

The role of serum IgG4 in the diagnosis, management and follow-up of patients with type 1 AIP. Moreover, data on other emerging biomarkers for type 1 and 2 AIP have been reported.

EXPERT OPINION

The diagnosis of AIP is challenging in clinical practice, especially for focal forms without multiorgan involvement, where distinction from pancreatic cancer can be difficult. Despite the strong association with type 1 AIP, serum IgG4 should only be measured when the suspicion for the disease is high, considering its limited sensitivity. New biomarkers with high diagnostic yield for both type 1 and type 2 AIP are needed.

Case Series of Autoimmune Pancreatitis and IgG4-Related Sclerosing Cholangitis

IgG4-related disease (IgG4-RD) is an emerging immune-mediated disease that can involve any organ. The involvement of the pancreas and biliary tract is the most common and well-studied in the literature. It is characterized by a non-specific presentation, mimicking a malignant process. The goal was to look at the different clinical and paraclinical aspects of this disease, as well as the challenges that come from its management. It was made up of three observations of patients with IgG4-RD involving the biliary tract and pancreas. The first observation concerned intrahepatic biliary cholangitis that was accompanied by porto-mesenteric thrombosis, which was discovered by cholestatic jaundice on the 15th day after an appendectomy, and the patient improved under corticosteroids and anticoagulants. The second observation concerned an acute revelation of the disease. It was an acute attack of chronic pancreatitis of IgG4-RD. The main symptoms were pancreatic pain and exocrine pancreatic insufficiency, and corticosteroid therapy allowed remission. The third observation was related to autoimmune pancreatitis (AIP) and IgG4-related sclerosing cholangitis, revealed by jaundice with cholestasis. The patient acquired corticosteroid resistance and an adverse progression to decompensated cirrhosis, and liver transplantation was indicated. The clinical presentation of IgG4-RD is heterogeneous, as evidenced by our three clinical observations. There are still significant gaps in our understanding, particularly in terms of pathogenesis and factors that influence therapy response. Further observational and interventional research is needed to better manage this disease.

American College of Rheumatology and the European League Against Rheumatism classification criteria for IgG4-related disease: an update for radiologists

IgG4-related disease (IgG4-RD) is an immune-mediated, multiorgan, chronic inflammatory disease. The three-step classification criteria proposed in 2019 by the American College of Rheumatology and the European League Against Rheumatism (ACR/EULAR) encompass a wide range of clinical, radiological, serological, and histopathological findings. The ACR/EULAR proposed a three-step classification process, i.e., entry step, exclusion step, and scoring system. Radiologists need to know that the radiological findings observed in the five domains of the lacrimal and salivary glands, chest, pancreas and biliary ducts, kidney, and retroperitoneum are independently weighted with different points in the scoring system. A total score < 20 points indicates that the patient should not be classified as having IgG4-RD; conversely, a total score ≥ 20 points indicates that the patient should be classified as having IgG4-RD. In this review, the 2019 ACR/EULAR classification criteria are discussed, focusing on the interpretation of each radiological item, with the aim of applying them to the diagnosis of IgG4-RD in clinical practice.

IgG4-related sialadenitis - a rare bilateral submandibular gland enlargement: case report

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition of unknown etiology. Although the salivary glands are currently considered among the most commonly affected among them, oral and maxillofacial surgeons are generally not familiar with the condition. Enlargement of the major salivary glands may be the first identifiable sign of IgG4-RD. A salivary gland biopsy along with IgG4 serum level assessment may help differentiate IgG4-related sialadenitis (IgG4-RS) from malignancies, infectious diseases, and obstructive conditions. Greater knowledge and higher levels of awareness of IgG4-RS may contribute to the expansion of differential diagnostic and treatment approaches. This case report describes a patient with bilateral submandibular salivary gland swelling who was diagnosed as having IgG4-RS on the basis of the histopathologic findings of a submandibular salivary gland biopsy and subsequent IgG4 levels.

The neurology of IGG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is emerging as a fibro-inflammatory entity affecting multiple organs, including manifold neurologic manifestations. This review discusses general characteristics of IgG4-RD neurologic disease including epidemiology, histology, clinical picture and treatment approaches.

RECENT FINDINGS

IgG4-RD is increasingly recognized as an important underlying pathophysiology in multiple disorders of neurologic interest, including orbital inflammation, infundibulo-hypophysitis, hypertrophic pachymeningitis, and even in rare cases CNS parenchymal disease and cranial vascular involvement. These were previously considered idiopathic and unrelated to any systemic disease but now known to share a common histopathology. New knowledge regarding the pathogenesis, clinical features and epidemiology of IgG4 is emerging, and new neurological manifestations continue to be described. Diagnostic progress includes CT-PET imaging, the use of flow cytometry for plasmablast quantification, and the use of reverse passive latex agglutination aiming to overcome the prozone phenomenon. Histopathologic confirmation of IgG4-RD remains the gold standard method of diagnosis but new diagnostic criteria for systemic and organ-specific disease are being proposed. Though glucorticoids remain the mainstay of therapy, relapses and incomplete recovery are frequent. Rituximab is a promising treatment in IgG4-RD that is severe, refractory or glucocorticoid dependent. Initiation of immunosuppression at an early stage of disease should be considered in order to avoid development of refractory fibrosis.

SUMMARY

The current review emphasizes the neurologic manifestations of IgG4-RD.

[IgG4-related disease: about 3 cases]

IgG4-Related disease (IgG4-RD), formerly known as IgG4-related autoimmune polyexocrinopathy, is a new condition including Plasminogen Activator Inhibitor-1 (PAI-1). It can affect different organs (central nervous system, salivary glands, thyroid, lungs, pancreas, bile ducts, liver, digestive tract, kidneys, prostate, etc.) with symptoms depending on the organ that is affected. It is more common in men older than 50 years of age. Its incidence and prevalence are poorly known because it is an uncommon disease. It is most common in Asia, accounting for only 20-30% of PAI in the Western world. Diagnosis is based on histological examination which shows dense lymphoplasmocytic infiltration in the organ affected associated with IgG4-positive plasma cells (immunohistochemistry), organ fibrosis and obliterating venulitis, all this in the context of increased serum IgG4 levels in more than 80% of cases. Patients are sensitive to corticosteroid therapy, with a high risk of relapse after discontinuation of corticosteroid therapy. This leads to the use of immunomodulators, mainly: thiopurines (azathioprine or 6-mercaptopurine), methotrexate and more recently rituximab, which can also be used as induction therapy. Given recent advances, accurate histological and clinical criteria are currently known to limit inappropriate management such as surgery. However, knowledge gaps remain concerning: pathophysiology, identification of specific biomarkers other than IgG4, natural history of the disease and long-term cancer risk assessment, performances of diagnostic tools such as endoscopic ultrasound-guided pancreatic biopsy. As well, consensual international management should be defined in the early stages of the disease and when patients develop recurrences. The purpose of this study was to report 3 cases of IgG4-Related disease on the basis of clinical and radiological criteria as well as therapeutic response.

Evaluate the Differences in CT Features and Serum IgG4 Levels between Lymphoma and Immunoglobulin G4-Related Disease of the Orbit

BACKGROUND

Benign immunoglobulin G4 (IgG4)-related orbital disease (IgG4-ROD)-characterized as tumors mimicking malignant orbital lymphoma (OL)-responds well to steroids, instead of chemotherapy, radiotherapy and/or surgery of OL. The objective of this study was to report the differences in computed tomography (CT) features and- serum IgG4 levels of IgG4-ROD and OL.

METHODS

This study retrieved records for patients with OL and IgG4-ROD from a pathology database during an eight-year-and-five-month period. We assessed the differences between 16 OL patients with 27 lesions and nine IgG4-ROD patients with 20 lesions according to prebiopsy CT features of lesions and prebiopsy serum IgG4 levels and immunoglobulin G (IgG) levels This study also established the receiver-operating curves (ROC) of precontrast and postcontrast CT Hounsfield unit scales (CTHU), serum IgG4 levels, serum IgG levels and their ratios.

RESULTS

Significantly related to IgG4-ROD (all p < 0.05) were the presence of lesions with regular borders, presence of multiple lesions-involving both lacrimal glands on CT scans-higher median values of postcontrast CTHU, postcontrast CTHU/precontrast CTHU ratios, serum IgG4 levels and serum IgG4/IgG level ratios. Compared to postcontrast CTHU, serum IgG4 levels had a larger area under the ROC curve (0.847 [95% confidence interval (CI): 0.674-1.000, p = 0.005] vs. 0.766 [95% CI: 0.615-0.917, p = 0.002]), higher sensitivity (0.889 [95% CI: 0.518-0.997] vs. 0.75 [95% CI: 0.509-0.913]), higher specificity (0.813 [95% CI: 0.544-0.960] vs. 0.778 [95% CI: 0.578-0.914]) and a higher cutoff value (≥132.5 mg/dL [milligrams per deciliter] vs. ≥89.5).

CONCLUSIONS

IgG4-ROD showed distinct CT features and elevated serum IgG4 (≥132.5 mg/dL), which could help distinguish IgG4-ROD from OL.

Differential diagnosis between pancreatic involvement in IgG4-related disease and pancreatic cancer

IgG4-related disease is a systemic disorder characterised by diffuse or tumoural inflammatory lesions. It can mimic pancreatic cancer, leading to errors in diagnosis and treatment increasing rates of morbidity and mortality in patients. The aim of this review is to take a differential diagnostic approach to these two entities using epidemiology, clinical and laboratory findings, imaging and histopathology.

Advances in the diagnosis and management of IgG4 related disease

IgG4 related disease was recognized as a unified disease entity only 15 years ago. Awareness of IgG4 related disease has increased worldwide since then, and specialists are now familiar with most of its clinical manifestations. Involvement of the pancreato-biliary tract, retroperitoneum/aorta, head and neck, and salivary glands are the most frequently observed disease phenotypes, differing in epidemiological features, serological findings, and prognostic outcomes. In view of this multifaceted presentation, IgG4 related disease represents a great mimicker of many neoplastic, inflammatory, and infectious conditions. Histopathology remains key to diagnosis because reliable biomarkers are lacking. Recently released classification criteria will be invaluable in improving early recognition of the disease. IgG4 related disease is highly treatable and responds promptly to glucocorticoids, but it can lead to end stage organ failure and even death if unrecognized. Prolonged courses of corticosteroids are often needed to maintain remission because the disease relapses in most patients. Rapid advancement in our understanding of the pathophysiology of IgG4 related disease is leading to the identification of novel therapeutic targets and possible personalized approaches to treatment.

[IgG4-related disease: what do we know after 20 years]

IgG4-related disease is immunomediated fibroinflammatory condition, characterized by tumefective lesions in different organs with distinctive pathomorphological features and IgG4 hypersecretion in serum and tissues in the majority of patients. IgG4-RD has been established as a separate clinical in the early 2000s. In the review we focus on the evolution of views on ethiopathogenesis of the disease, therapeutic and diagnostic options and classification of the disease.

Clinical utility of serum IgG4 measurement

This article will review the structure and function of IgG4, methods of measuring serum IgG4 concentrations, clinical conditions associated with increased and decreased serum IgG4, and the test characteristics of serum IgG4 in the diagnosis and management of Immunoglobulin G4-Related Disease (IgG4-RD). The four subclasses of IgG were discovered in 1964 through experiments on monoclonal IgG in patients with myeloma. Since 2001, interest in measuring serum IgG subclasses has increased dramatically due to the emergence of IgG4-RD, a multisystem fibroinflammatory condition wherein polyclonal serum IgG4 concentration is increased in approximately 70% of cases. Increased serum IgG4 typically manifests as a restriction in the anodal gamma region on serum protein electrophoresis, often with beta-gamma bridging, and can be mistaken as a monoclonal protein or polyclonal increase in IgA. Limitations of current clinical methods used in quantitation of serum IgG4 concentrations will be discussed, including the common immunonephelometric assays and LC-MS/MS based assays. Polyclonal IgG4 elevation is not specific for IgG4-RD, and may also occur in conditions such as eosinophilic granulomatosis with polyangiitis (EGPA), lymphoma, and multicentric Castleman disease (MCD). Race and gender differences also affect interpretation of serum IgG4 concentrations, for instance Asians have a higher serum IgG4 concentration than Whites and males have a higher concentration than females.

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.

Evaluation of a novel serum IgG4 assay and determination of reference interval for the Japanese population

BACKGROUND

IgG4-related disease (IgG4-RD) is a new syndrome characterized by elevated serum IgG4 concentration and tissue infiltration of IgG4-positive plasma cells. Here, we evaluated the analytical performance of a new IgG4 assay reagent featuring a wide dynamic range, highly specific monoclonal antibody, and the reversed passive latex agglutination assay and determined the IgG4 reference interval (RI) for the Japanese population.

METHODS

Performance evaluations were conducted on precision, linearity, sensitivity, interference, and method comparison with The Binding Site (TBS) and Siemens reagents. The RI was derived by the parametric method from 619 apparently healthy Japanese 18 to 65 years of age.

RESULTS

Between-day precisions ranged from 1.99 to 5.52 CV%. Linearity was confirmed up to 5.0 g/l. The limit of quantitation was 0.085 g/l. Interfering substances did not significantly influence values. Method comparison among the 3 reagents yielded correlation coefficients between 0.973 and 0.988. Values for the new reagent matched those of TBS reagent except at a higher concentration range, where reactivity dissociated. The RI was 0.11-1.21 g/l without distinction by sex and age.

CONCLUSION

The novel IgG4 assay reagent demonstrated satisfactory analytical performance for clinical use. Because of matched value with TBS reagent at low concentrations, it is possible to use the IgG4-RD cut-off value determined by TBS reagent.

The treatment outcomes in IgG4-related orbital disease: a systematic review of the literature

IgG4-related disease (IgG4-RD) is an immune-mediated systemic fibro inflammatory disease. Treatment of IgG4-related orbital disease (IgG4-ROD) is often indicated to relieve the symptoms and to prevent complications. For IgG4-ROD, no international formal treatment guidelines are available and the optimal treatment strategy is uncertain. In this systematic review, we describe the efficacy of conventional and biologic disease-modifying antirheumatic drugs (DMARDs) in IgG4-ROD. A systematic search of Embase, Medline, Web-of-Science, PubMed publisher, Cochrane and Google Scholar was performed for treatment outcomes in IgG4-ROD. Relevant articles on treatment of IgG4-ROD were retrieved to last date of inclusion 3 January 2018. The following inclusion criteria were used: articles in English or English translation, studies evaluating the use of DMARDs (conventional and biologic) in the treatment of IgG4-ROD. Meta-analysis and review articles were excluded. A final selection after full-text evaluation was made by independent reviewers, based on treatment of IgG4-ROD with DMARDs and the availability of treatment outcomes. With this systematic review, we identified 35 studies and case reports/series on IgG4-ROD, describing 95 patients, treated with conventional and/or biologic DMARDs. The success of conventional DMARDs varies between 36% and 75% in patients with IgG4-ROD, while rituximab is successful in the majority (93%) of the patients. Based on this systematic review, rituximab is the most effective DMARD in IgG4-ROD, while the efficacy of conventional DMARDs is limited. We propose early initiation of rituximab in case of refractory and organ- or life-threatening disease.

IgG4-related disease with pseudotumor formation in the larynx

Mikulicz's disease, an immunoglobulin G4-related disease (IgG4-RD) occurs frequently in the head and neck region but rarely in the larynx. We report a case of IgG4-RD with pseudotumor formation in the larynx. A 50-year-old man presented at our facility for a complete physical examination and diagnostic testing of a left arytenoid tumor. On examination, a large supraglottic mass was noted with signs of dyspnea. Movement disorder of the vocal fold was absent. The patient underwent surgery with general anesthesia to improve respiratory symptoms and a resected specimen was submitted for diagnosis. The pathology findings revealed lymph follicle formation, interstitial follicular fibrosis, angiogenesis, and inflammatory cell infiltration with plasmacytosis. Immunohistologic staining at high magnification revealed one hundred or more IgG4-positive plasma cells and fifty percent IgG4/IgG. In addition, obliterative phlebitis was observed. Medical history was positive for retroperitoneal fibrosis with serum IgG4 levels below the diagnostic criteria of IgG4-RD, but histological characteristics of IgG4-RD were met. The diagnosis of IgG4-RD was established, oral treatment with prednisolone (0.6 mg/kg/day) was initiated, and the tumor reduced in size. IgG4-RD may cause irreversible functional impairment. Early diagnosis and treatment are important in reducing the risk of permanent impairment of vocal fold mobility.

IgG4-Related Kidney Disease: A Curious Case of Interstitial Nephritis with Hypocomplementemia

IgG4-related kidney disease has been relatively newly recognized over the last two decades as a combination of an autoimmune and allergic disorder, with elevated serum IgG4 level and hypocomplementemia among its characteristic features. Here we report the case of a man with interstitial nephritis presenting with acute kidney injury and hypocomplementemia but normal serum IgG4 level and provide a literature review of IgG4-related kidney disease. This case highlights the importance of IgG4-related kidney disease as an important differential diagnosis in any patient presenting with a clinical syndrome mimicking acute interstitial nephritis with hypocomplementemia. A high index of suspicion with a low threshold for performing a native kidney biopsy would be paramount as patients do respond well to corticosteroid therapy.

IgG4-Related Disease with Emphasis on Its Gastrointestinal Manifestation

IgG4-related disease is an immune-mediated fibroinflammatory condition with a diverse spectrum of organ involvement, commonly in the pancreas and bile ducts among other organs such as salivary and lacrimal glands. Classic histopathologic findings are the gold standard for confirmation of diagnosis, although diagnosis remains challenging, as biomarkers to date are neither sufficient nor necessary. Glucocorticoids are the most effective initial treatment, generally having a dramatic response, although limited clinical evidence exists regarding effective maintenance therapy. This review summarizes key GI manifestations of this condition for the practicing gastroenterologist and addresses the pathology, disease mechanism, and current therapeutic recommendations.

[Clinical and laboratory characteristics of IgG4-realated disease and its diagnostic algorithm]

AIM

to propose diagnostic algorithm of IgG4-related disease (IgG4-RD).

MATERIALS AND METHODS

One center retrospective research. 52 pts with IgG4-RD were included. The diagnosis was proved histologically and immunohistochemically. 48 out of 52 pts received treatment. Treatment included one of the following schemes (along with low oral glucocorticoids): rituximab monotherapy, cyclophosphamide monotherapy or their combination.

RESULTS

The mean age was 47.4±5.9 years, the mean age of the disease onset was 43.9±16.0 years. Median time before the diagnosis was 24 months. The most often sites of IgG4-RD were lacrimal (63.5%), salivary (46.2%) glands, lungs (48%), lymph nodes (34.6%) and retroperitoneum (17.3%). In clinical picture the leading complain was organ enlargement, but not its dysfunction. Pain was characteristic for retroperitoneum localization. In 56.8% of pts with IgG4-related syalo - and/or dacryoadenitis there was association with ear - nose - throat organs affection. In 4 pts (7.7%) IgG4-RD was combined with some malignant disease, including MALT-lymphoma of lacrimal glands. Irreversible organ damage as an IgG4-RD outcome had 15.4% of pts. The main laboratory markers of IgG4-RD were ESR elevation (38.5%), blood eosinophilia (9.6%), immunological disturbances (serum total IgG and IgG4 elevation, IgE elevation, antinuclear antibodies, rheumatoid factor detection, hypocomplementemia). Serum IgG4 level >1.35 g/l was elevated in 88% of pts and correlated with the number of affected organs (Spearman correlation coefficient 0.39, Student's test, р=0.0056). Monoclonal serum secretion and B-cell clonality in the tissue was detected in 4 (23.5%) out of 17 pts, but not all of them had both signs.

CONCLUSION

Based on the analysis of clinical and laboratory characteristics of IgG4-RD a diagnostic algorithm was proposed that enhances the detection and examination of the patients with suspected IgG4-RD.

IgG4-related disease: what a hematologist needs to know

IgG4-related disease is a fibro-inflammatory condition that can affect nearly any organ system. Common presentations include major salivary and lacrimal gland enlargement, orbital disease, autoimmune pancreatitis, retroperitoneal fibrosis and tubulointerstitial nephritis. This review focuses on the hematologic manifestations of IgG4-related disease, including lymphadenopathy, eosinophilia, and polyclonal hypergammaglobulinemia. The disease can easily be missed by unsuspecting hematologists, as patients may present with clinical problems that mimic disorders such as multicentric Castleman disease, lymphoma, plasma cell neoplasms and hypereosinophilic syndromes. When IgG4-related disease is suspected, serum protein electrophoresis and IgG subclasses are helpful as initial tests but a firm histological diagnosis is essential both to confirm the diagnosis and to rule out mimickers. The central histopathological features are a dense, polyclonal, lymphoplasmacytic infiltrate enriched with IgG4-positive plasma cells (with an IgG4/IgG ratio >40%), storiform fibrosis, and obliterative phlebitis. Importantly for hematologists, the latter two features are seen in all tissues except bone marrow and lymph nodes, making these two sites suboptimal for histological confirmation. Many patients follow an indolent course and respond well to treatment, but a significant proportion may have highly morbid or fatal complications such as periaortitis, severe retroperitoneal fibrosis or pachymeningitis. Corticosteroids are effective but cause new or worsening diabetes in about 40% of patients. Initial response rates to rituximab are high but durable remissions are rare. More intensive lymphoma chemotherapy regimens may be required in rare cases of severe, refractory disease, and targeted therapy against plasmablasts, IgE and other disease biomarkers warrant further exploration.

New insights into the pathophysiology of IgG4-related disease and markers of disease activity

INTRODUCTION

Recently, IgG4-related disease (IgG4-RD) has become a well-recognized clinical entity, although its causes are still not well understood. The pathophysiology of IgG4-RD has been reported from a variety of aspects. Areas covered: In this review, we outline a number of recent advances in our understanding of the pathogenesis of IgG4-RD, divided according to acquired immunology and innate immunology and other topics. Furthermore, we also focus on some proposed markers of disease activity of IgG4-RD. Expert commentary: One striking advance made recently is the identification of novel autoantigens of IgG4-RD. At the onset of IgG4-RD, various T cell side factors such as Tfh, Th2 cells are at work, in addition to B cell side factors like plasmablasts and plasma cells, and innate immunology via TLR and M2 macrophages. The efficacy of B cell depletion therapy using rituximab has been reported, with the establishment of steroid-sparing therapies targeting other molecules also anticipated.

Neuro-ophthalmic complications of IgG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is increasingly recognized as a fibroinflammatory disease with a plethora of organ-specific manifestations but a particular predilection for head and neck tissues, including the nervous system. This review discusses general features and organ-specific presentations of IgG4-RD as well as treatment considerations, particularly emphasizing features of neuro-ophthalmic interest.

RECENT FINDINGS

IgG4-RD is emerging as a common cause of several fibroinflammatory disorders in the head and neck that were previously considered idiopathic, such as sclerosing orbital pseudotumor, orbital myositis, hypophysitis, and hypertrophic pachymeningitis. New and unusual presentations continue to be described, including a number of vascular manifestations. Substantial progress has been made in elucidating the cell types involved in IgG4-RD, and new pathogenic models are being proposed. Although clinicopathologic correlation remains the cornerstone of diagnosis, ancillary tests such as flow cytometry for circulating plasmablasts and PET-computed tomography have high sensitivity, and certain radiologic features are recognized to be particularly suggestive, such as infraorbital nerve enlargement in IgG4-RD orbitopathy. IgG4-RD often responds to steroids but incomplete responses and relapses are common. Rituximab is emerging as a promising new therapy.

SUMMARY

The current review summarizes manifestations of IgG4RD that are of particular relevance to neuro-ophthalmic practice.

Unique properties of IgG4 antibody and its clinical application in autoimmune pancreatitis

BACKGROUND

Autoimmune pancreatitis (AIP) is defined as a unique form of chronic pancreatitis characterized by clinical presentation with obstructive jaundice, a dense lymphoplasmacytic infiltrate and fibrosis histologically, and a dramatic response to steroids therapeutically. The possible role of IgG4 in driving the pathology of AIP is a controversial subject that has not been addressed satisfactorily.  Objective: The purpose of this review is to discuss the unique biology of IgG4 that are important for its role and the clinical applications for serologic detection.

METHODS

Review of current literature about IgG4 antibody in the clinical application in AIP.

RESULTS

High serum levels of IgG4 are an important biomarker and broadly used for diagnosis, differentiation from diseases especially pancreatic cancer, and as a parameter to indicate disease activity, extra-pancreatic lesions, and treatment monitoring. However, some controversial studies show it has a limited specificity and sensitivity in these conditions.  Conclusion: Although increasing studies have promoted our understanding of the structure and function of IgG4, there is still dilemma between the beneficial and the adverse aspect of IgG4 in the pathogenesis of AIP.

Colon cancer and IgG4-related disease with orbital inflammation and bilateral optic perineuritis: A case report

RATIONALE

Immunoglobulin G4-related disease (IgG4-RD) is an inflammatory condition of unknown cause. Cancer might be related to the development of certain IgG4-RD but to date, little literature documents it.

PATIENT CONCERNS

A 78-year old man presented with unilateral proptosis responsive to steroids, initially attributed to nonspecific orbital inflammation.

DIAGNOSIS

Right hemicolectomy was performed because of a suspicious lesion which turned out to be tubulovillous adenoma on histological analysis. Eight months after the surgery, a mass infiltrating the mesentery was found and biopsy revealed IgG4-RD.

INTERVENTIONS

Both the orbital inflammation and abdominal mass infiltrating the mesentery were responsive to steroids and rituximab administered to treat IgG4-RD.

OUTCOMES

In the course of IgG4-RD, the patient developed bilateral optic perineuritis, causing bilateral visual loss. Colon cancer with synchronous multiple liver metastases was found 1 year after rituximab treatment.

LESSONS

This case raises the possibility of IgG4-RD being a paraneoplastic syndrome in some patients. Cancer screening should probably be performed in some elderly patients diagnosed with IgG4-RD.

Inferior vena cava thrombosis as the initial presentation of IgG4-related retroperitoneal fibrosis: Case report and literature review

IgG4-related disease is an immune-mediated deposition of fibro-inflammatory tissue with IgG4-positive plasma cells and dense fibrosis in a single or multiple organs. It often raises concern for malignancy requiring biopsy for diagnosis. Presentation may vary according to organ involved. IgG4-related retroperitoneal fibrosis accounts for two-thirds of the previously considered idiopathic retroperitoneal fibrosis cases. In IgG4-related retroperitoneal fibrosis, computed tomography scan or magnetic resonance imaging shows periaortic soft tissue that extends from below the kidneys to iliac arteries and entrap ureters causing hydronephrosis and renal failure. We present a rare case of IgG4-related retroperitoneal fibrosis presenting with leg swelling and pain due to inferior vena cava compression and thrombosis, and we review current concepts on disease pathogenesis, diagnosis and treatment.

Clinicoserological factors associated with response to steroid treatment and recurrence in patients with IgG4-related ophthalmic disease

Purpose

To investigate the factors associated with response to steroid treatment and recurrence in patients with IgG4-related ophthalmic disease (ROD).

Methods

Twenty-eight patients with biopsy-proven IgG4-ROD treated between March 2010 and January 2017 were included in this retrospective study. Clinical features, serum IgG4 levels, systemic involvement, treatments and treatment outcome, factors associated with response to treatment and recurrence were assessed.

Result

Thirteen men and 15 women (mean age 50.8 years) were evaluated over mean follow-up period of 27.3 months. Elevated serum IgG4 levels (>1.35 g/L) and systemic disease were noted in 9 (32%) and 18 patients (64%), respectively. The lacrimal gland was involved in all patients, and 22 patients (78.6%) had bilateral involvement. Most patients (82%) responded well to systemic steroids, but 12 (43%) relapsed after the initial steroid treatment, requiring additional therapies to achieve remission. Complete response to initial steroid treatment was associated with elevated serum IgG4 levels before treatment (P=0.001) and bilateral orbital involvement (P=0.050). Recurrence was associated with elevated serum IgG4 levels before treatment (P=0.007), lower dose (P=0.057) and shorter duration of initial steroids (P=0.042). Patients with recurrence eventually required significantly more steroids than those without recurrence (P=0.011).

Conclusions

Patients with IgG4-ROD responded well to systemic steroid treatment, but recurrence was common, particularly among those with elevated serum IgG4 levels and shorter duration of initial steroid treatment. Low-dose maintenance treatment with systemic steroids should be considered to avoid recurrence in patients with elevated serum IgG4 levels.

Resolution of Spurious Immunonephelometric IgG Subclass Measurement Discrepancies by LC-MS/MS

BACKGROUND

The Binding Site immunonephelometric (IN) IgG subclass reagents (IgG1, IgG2, IgG3, IgG, BSIN) are used for assessment of both immunodeficiency and IgG4-related disease (IgG4-RD). In our laboratory, suspected analytic errors were noted in patients with increases in IgG4: The sum of the individual IgG subclasses was substantially greater than the measured total IgG concentrations (unlike samples with normal IgG4), and the IgG4 concentration was always less than the IgG2 concentration.

METHODS

We developed a tryptic digest LC-MS/MS method to quantify IgG1, IgG2, IgG3, and IgG4 in serum. Samples with IgG4 concentrations ranging from <0.03 g/L to 32 g/L were reanalyzed by LC-MS/MS, and a subset was also reanalyzed by Siemens IN (SIN) subclass measurements.

RESULTS

Multivariate linear regression identified 3 subclass tests with multiple predictors of the measured subclass concentration. For these 3 subclasses, the predominant predictors were (in terms of LC-MS/MS IgG subclass measurement coefficients) BSIN IgG1 = 0.89·IgG1 + 0.4·IgG4; BSIN IgG2 = 0.94·IgG4 + 0.89·IgG2; and SIN IgG2 = 0.72·IgG2 + 0.24·IgG4.

CONCLUSIONS

There is apparent IgG4 cross-reactivity with select IN subclass measurements affecting tests from both vendors tested. These findings can be explained either by direct cross-reactivity of the IN reagents with the IgG4 subclass or unique physicochemical properties of IgG4 that permit nonspecific binding of IgG4 heavy chain to other IgG immunoglobulin heavy chains. Irrespective of the mechanism, the observed intermethod discrepancies support the use of LC-MS/MS as the preferred method for measurement of IgG subclasses when testing patients with suspected IgG4-RD.

Update in ethiopathogeny, diagnosis and treatment of the IgG4 related disease

IgG4 related disease (IgG4-RD) is probably an autoimmune pathology of unknown etiology. Diverse interactions participate in its pathogen between the adaptive and innate immune systems, activating lymphocytes B and T which trigger the inflammatory cascade, which culminates in fibrosis of the organs and their malfunction. It can affect a multitude of organs simultaneously. The diagnosis is based on the correlation of clinical findings with anatomopathological results (lymphoplasmocitary infiltrate, storiform fibrosis, obliterative phlebitis and IgG4+plasmatic cell count) and with the presence of elevated IgG4 in serum, depending on the criteria used. Corticoids and rituximab are among the few validated treatments available. There are multiple biomarkers and treatments in development. In this review, we aim to go over the principal pathogenic and clinical characteristics of IgG4-RD, as well as its handling, in accordance with the available scientific evidence.

Is Graves' disease a primary immunodeficiency? New immunological perspectives on an endocrine disease

BACKGROUND

Uncertainty about factors influencing the susceptibility and triggers for Graves' disease persists, along with a wide variation in the response to anti-thyroid drugs, currently at approximately 50% of non-responders. The aim of this narrative review is to summarize immunological concepts, with a combined endocrine and immunological perspective, to highlight potential new areas of research.

MAIN TEXT

Relevant studies were identified through a systematic literature search using the PubMed and EMBASE databases in March 2016. No cut-offs regarding dates were imposed. We used the terms "Graves' Disease" or "Basedow" or "thyrotoxicosis" together with the terms "etiology", "pathophysiology", "immunodeficiency", "causality", and "autoimmunity". The terms "orbitopathy", "ophthalmopathy", and "amiodarone" were excluded. Articles in English, French, German, Croatian, Spanish, and Italian were eligible for inclusion.

CONCLUSIONS

While concepts such as the impact of iodine, smoking, human leucocyte antigen, infections, and ethnicity are established, new ideas have emerged. Pertaining evidence suggests the involvement of autoimmunity and immunodeficiency in the pathophysiology of Graves' disease. Recent studies point to specific immunological mechanisms triggering the onset of disease, which may also serve as targets for more specific therapies.

Increases in IgE, Eosinophils, and Mast Cells Can be Used in Diagnosis and to Predict Relapse of IgG4-Related Disease

BACKGROUND & AIMS

IgG subclass 4-related disease (IgG4-RD) is characterized by increased serum levels of IgG4 and infiltration of biliary, pancreatic, and other tissues by IgG4-positive plasma cells. We assessed the prevalence of allergy and/or atopy, serum, and tissue IgE antibodies, and blood and tissue eosinophils in patients with IgG4-RD. We investigated the association between serum IgE and diagnosis and relapse of this disease.

METHODS

We performed a prospective study of 48 patients with IgG4-RD, 42 patients with an increased serum level of IgG4 with other inflammatory and autoimmune conditions (disease control subjects), and 51 healthy individuals (healthy control subjects) recruited from Oxford, United Kingdom from March 2010 through March 2014, and followed for a median of 41 months (range, 3-73 months). Serum levels of immunoglobulin were measured at diagnosis, during steroid treatment, and at disease relapse for patients with IgG4-RD; levels at diagnosis were compared with baseline levels of control subjects. Allergen-specific IgEs were measured using the IgE ImmunoCAP. Levels and distribution of IgG4 and IgE antibodies in lymphoid, biliary, and pancreatic tissues from patients with IgG4-RD and disease control subjects were measured by immunohistochemistry. We analyzed data using the Spearman rank correlation and receiver operating characteristic curves.

RESULTS

Serum levels of IgG4 increased to 1.4 g/L or more, and IgE increased to 125 kIU/L or more, in 81% and 54% of patients with IgG4-RD, respectively, compared with 6% and 16% of healthy control subjects (P < .0001). Peripheral blood eosinophilia was detected in 38% of patients with IgG4-RD versus 9% of healthy control subjects (P = .004). Of patients with IgG4-RD, 63% had a history of allergy and 40% had a history of atopy with an IgE-specific response; these values were 60% and 53% in patients with increased serum levels of IgE (P < .05). Level of IgE at diagnosis >480 kIU/L distinguished patients with IgG4-RD from disease control subjects with 86% specificity, 36% sensitivity, and a likelihood ratio of 3.2. Level of IgE at diagnosis >380 kIU/L identified patients with disease relapse with 88% specificity, 64% sensitivity, and a likelihood ratio of 5.4. IgE-positive mast cells and eosinophilia were observed in lymphoid, biliary, and pancreatic tissue samples from 50% and 86% of patients with IgG4-RD, respectively.

CONCLUSIONS

In a prospective study, we associated IgG4-RD with allergy, atopy, eosinophilia, increased serum levels of IgE, and IgE-positive mast cells in lymphoid, biliary, and pancreatic tissue. An IgE-mediated allergic response therefore seems to develop in most patients with IgG4-RD; levels of IgE might be used in diagnosis and predicting relapse.

A Challenging Diagnosis of IgG4-Related Disease When Understanding Limitations of Laboratory Testing Was Pivotal

A 76-year-old man was incidentally found on a CT scan to have lymphadenopathy and bilateral kidney enlargement suggestive of infiltrative renal disease. He was largely asymptomatic but had bilateral salivary and lacrimal gland enlargement. A grossly elevated serum IgG (>70 g/L) with concomitant suppression of other immunoglobulins, a small IgG restriction, and a parotid biopsy revealing lymphoplasmacytic infiltrate with slight kappa light chain excess all suggested a lymphoproliferative disorder (LPD). The diagnostic workup was further confounded by a normal serum IgG4 concentration. Moreover, bone marrow and renal biopsies did not reveal evidence of LPD. Discussion with the laboratory not only clarified that the markedly increased total IgG could not be accounted for by the small IgG restriction, but also identified a discrepancy in the IgG4 measurement. Repeat analysis of a follow-up sample revealed an elevated IgG4 of 5.94 (reference interval: 0.039–0.864) g/L, which prompted a repeat parotid biopsy that showed predominant IgG4+ lymphocytic infiltrates. Despite the deluding presentations, a final diagnosis of IgG4-related disease (IgG4-RD) was made based on elevated serum IgG4 concentrations and histopathological findings. This case highlights the importance of recognizing limitations of laboratory testing and the benefit of close communications among clinical subspecialties and the laboratory.

Expansion of blood IgG4+ B, TH2, and regulatory T cells in patients with IgG4-related disease

BACKGROUND

IgG₄-related disease (IgG₄-RD) is a systemic fibroinflammatory condition affecting various organs and has a diverse clinical presentation. Fibrosis and accumulation of IgG₄⁺ plasma cells in tissue are hallmarks of the disease, and IgG₄-RD is associated with increased IgG₄ serum levels. However, disease pathogenesis is still unclear, and these cellular and molecular parameters are neither sensitive nor specific for the diagnosis of IgG₄-RD.

OBJECTIVE

Here we sought to develop a flow cytometric gating strategy to reliably identify blood IgG₄⁺ B cells to study their cellular and molecular characteristics and investigate their contribution in disease pathogenesis.

METHODS

Sixteen patients with histologically confirmed IgG₄-RD, 11 patients with sarcoidosis, and 30 healthy subjects were included for 11-color flow cytometric analysis of peripheral blood for IgG₄-expressing B cells and T_H subsets. In addition, detailed analysis of activation markers and chemokine receptors was performed on IgG₄-expressing B cells, and IgG₄ transcripts were analyzed for somatic hypermutations.

RESULTS

Cellular and molecular analyses revealed increased numbers of blood IgG₄⁺ memory B cells in patients with IgG₄-RD. These cells showed reduced expression of CD27 and CXCR5 and increased signs of antibody maturation. Furthermore, patients with IgG₄-RD, but not patients with sarcoidosis, had increased numbers of circulating plasmablasts and CD21^low B cells, as well as T_H2 and regulatory T cells, indicating a common disease pathogenesis in patients with IgG₄-RD.

CONCLUSION

These results provide new insights into the dysregulated IgG₄ response in patients with IgG₄-RD. A specific "peripheral lymphocyte signature" observed in patients with IgG₄-RD, could support diagnosis and treatment monitoring.

Diagnostic and treatment workup for IgG4-related disease

INTRODUCTION

IgG4-Related Disease is a newly recognized condition which is increasingly diagnosed by practitioners due to improvement in clinical awareness. Men and women have been found to be affected by this disease in various organs, more commonly with involvement of the salivary and lacrimal glands as well as pancreas and liver. Areas covered: The diagnosis and management of this condition remain challenging as biomarkers and therapies are being investigated. Hallmark features on histology are still the gold standard for confirmation of diagnosis, whereas serum IgG4 level has been shown to be neither necessary nor sufficient for the diagnosis. Glucocorticoids remain the most effective initial management for this condition while there are limited clinical trials on the effectiveness of maintenance therapy. Expert commentary: This review serves as an update on approaches for diagnosis and management of IgG4-RD. Most of the known data in this field comes from retrospective cohort studies and expert consensus guidelines but new ongoing prospective studies, clinical trials and better understanding of the pathogenesis of this condition are promising.

Neurological Manifestations of IgG4-Related Disease

OPINION STATEMENT

IgG4-related disease (IgG4-RD) is a multisystem inflammatory disorder. Early recognition of IgG4-RD is important to avoid permanent organ dysfunction and disability. Neurological involvement by IgG4-RD is relatively uncommon, but well recognised-hypertrophic pachymeningitis and hypophysitis are the most frequent manifestations. Although the nervous system may be involved in isolation, this more frequently occurs in conjunction with involvement of other systems. Elevated circulating levels of IgG4 are suggestive of the condition, but these are not pathognomonic and exclusion of other inflammatory disorders including vasculitis is required. Wherever possible, a tissue diagnosis should be established. The characteristic histopathological changes include a lymphoplasmacytoid infiltrate, storiform fibrosis and obliterative phlebitis. IgG4-RD typically responds well to treatment with glucocorticoids, although relapse is relatively common and treatment with a steroid-sparing agent or rituximab may be required. Improved understanding of the pathogenesis of IgG4-RD is likely to lead to the development of more specific disease treatments in the future.

Comparative Study of Clinical, Pathological, Radiological, and Genetic Features of Patients With Adult Ocular Adnexal Xanthogranulomatous Disease, Erdheim-Chester Disease, and IgG4-Related Disease of the Orbit/Ocular Adnexa

PURPOSE

To compare and contrast the clinical, radiologic, pathologic, and genetic features of patients with ocular adnexal IgG4-related disease (IgG4-RD) and patients with adult ocular adnexal xanthogranulomatous disease (XG).

METHODS

This retrospective review study identified patients with histological evidence of either disease from records of the pathology department of our hospital from 1996 to 2014. Clinical, imaging, and a variety of histopathologic features were collected for 23 patients with IgG4-RD and 13 patients with XG. Next generation sequencing with a 50-gene cancer screening panel was performed on biopsy tissues from 10 patients in each group.

RESULTS

Statistical differences between the 2 groups include eyelid (67%; p = 0.0002) and anterior orbital (75%; p = 0.0352) predilection for XG except for Erdheim-Chester disease subgroup which was more posterior and diffuse. Eyelid involvement was rare (4%) for IgG4-RD. Involvement of orbital nerves was seen in 30% of IgG4-RD and 0% in XG (p = 0.0695). Five patients with IgG4-RD developed malignancy (4 lymphoma, 1 leiomyosarcoma), but none of XG patients. Discriminating pathological features were the presence of any IgG4+ plasma cells (p = 0.0121) and the ratio of IgG4+/IgG+ plasma cells (p =0.0294) for IgG4-RD. Five of 12 (42%) patients with XG had sufficient numbers of IgG4+ plasma cells/high power field to fulfill published diagnostic criteria for IgG4-RD, and 5 (42%) had a ratio of IgG4+/IgG+ plasma cells over 40%, but the numbers overall were less than seen in the IgG4-RD patients. The only genetic difference between the 2 groups was that BRAF V600E mutation was found in 1 of the 2 Erdheim-Chester disease patients, which form a subgroup of XG.

CONCLUSIONS

IgG4-RD and XG share clinical, imaging, and histopathological features including IgG4+ plasma cells. Significant differences were the eyelid involvement in XG, orbital nerve involvement, and an elevated IgG4+/IgG+ ratio in IgG4-RD and the only genetic abnormality found was BRAF V600E mutation in the Erdheim-Chester disease subgroup of XG.

IgG4-Related Tubulointerstitial Nephritis

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a fibroinflammatory disorder that can involve nearly any organ. The disorder has increasingly become known as a distinct clinical entity during the last decade. IgG4-related tubulointerstitial nephritis (IgG4-TIN) is the most common manifestation of IgG4-RD in the kidney. Many patients with IgG4-TIN are diagnosed after IgG4-RD has been recognized in other organ systems, but the kidney may also be the first or only site involved. The presenting clinical features of IgG4-TIN are most commonly kidney insufficiency, kidney mass lesion(s), or both. On biopsy, IgG4-TIN shows a dense lymphoplasmacytic infiltrate, increased IgG4+ plasma cells, storiform fibrosis, and often tubular basement membrane immune complex deposits. Elevation of serum IgG4 often accompanies IgG4-RD; however, it is not specific in reaching the diagnosis. Like IgG4-RD in other organs, IgG4-TIN characteristically responds promptly to steroids, although there is a high relapse rate on discontinuation of immunosuppression. The pathogenesis of IgG4-RD is not understood.

Recent advances in understanding and managing IgG4-related disease

IgG4-related disease was only recently discovered, so its description, management, and new discoveries related to its etiology are rapidly evolving. Because IgG4 itself is a unique antibody which is intimately related to the diagnosis of the disease, the role of plasmablasts in the pathophysiology remains an active area of discussion. Recent studies have uncovered a possible role for CD4-positive cytotoxic T lymphocytes, T follicular helper cells, and M2 macrophages. The clinical presentation is variable and can be vague, as this disease affects many organs and new presentations are continuing to be described. The diagnosis depends on clinical and histopathological assessment. The mainstay of treatment is with glucocorticoids, but rituximab has recently shown promise. Monitoring disease activity using imaging modalities (including positron emission tomography) and serum markers is imperative, as relapses are common. IgG4-related disease spans many medical disciplines but is a treatable condition with which all clinicians should be familiar.