International Consensus Guidance Statement on the Management and Treatment of IgG4-Related Disease

Rapidly Progressive Kidney Failure Associated with Perirenal Capsular Lesion Due to IgG4-Related Disease

A 71-year-old Japanese man with progressive kidney failure was referred to our hospital. Laboratory tests showed elevated IgG4 levels. Contrast-enhanced computed tomography (CT) revealed soft tissue surrounding the left kidney and right atrophic kidney. A histopathological examination revealed inflammation and fibrosis with rich IgG4-positive cells in the thickened kidney capsule, but not in the kidney parenchyma. Poor enhancement in the left kidney on contrast-enhanced CT and wrinkling of glomerular capillaries in pathological tissues were also observed. These findings indicated IgG4-related perirenal lesions leading to low renal perfusion and kidney failure. The perirenal lesions and kidney failure were improved by corticosteroid therapy.

A 33-Year-Old Man With Dyspnea, Chest Pain, and a Massive Pleural Effusion

CASE PRESENTATION

A 33-year-old white man presented to the ED with 1-month history of worsening dyspnea. He experienced gradual onset of right-sided scapular pain and shortness of breath on exertion that progressively worsened over the course of 1 month. He had a mild nonproductive cough and intermittent subjective fevers and reported weight loss of approximately 2 kg over 1 month. He had a history of two episodes of acute pancreatitis that was thought to be autoimmune in origin. He was a never smoker; he denied illicit drug use or recent alcohol consumption. He had no known TB exposure, but his mother had a history of sarcoidosis.

IgG4-Related Disease and the Salivary Glands: A Review of Pathophysiology, Diagnosis, and Management

IgG4-related disease is a rare, immune-mediated, systemic disease that is characterized by soft tissue lymphocyte infiltration and resultant fibrosis. The salivary glands are among the most commonly affected organs. Patients present with subacute submandibular and/or parotid swelling and sialadenitis. Diagnosis incorporates clinical, serologic, radiologic, and pathologic findings. Most cases respond quickly to systemic glucocorticoids. IgG4-related disease mimics many infectious, inflammatory, and neoplastic diseases. Therefore, IgG4-related disease is frequently misdiagnosed. A knowledge of the pathophysiology, diagnosis, and management of IgG4-related disease is important for providers who treat salivary gland diseases.

Synchronous occurrence of IgG4-related sialadenitis and ductal carcinoma of the parotid gland: a case report

Immunoglobulin G4-related disease (IgG4-RD) is a rare chronic systemic inflammatory pathology that poses a diagnostic challenge since it can simulate malignancy when it affects a salivary gland as a mass-like lesion. Here, the authors report an unusual clinical case of a 42-year-old man who presented with a painless, slow-growing swelling located in the right parotid gland with a 12-month evolution. Based on imaging tests and open biopsy, a diagnosis of chronic parotitis was presumed and oral methylprednisolone was prescribed. Due to poor response to medication, a total parotidectomy preserving the facial nerve was performed. The final pathology described a unilateral IgG4-related sialadenitis (IgG4-RS) in the parotid gland in combination with a poorly differentiated multifocal ductal carcinoma. The postoperative course was uneventful except for a temporary facial paresis (grade III according to the House-Brackmann classification system) that resolved completely within 5 months. There were no systemic manifestations on the whole-body 18F-FDG PET/CT. Adjuvant radiotherapy was administered without complications. Twenty-four months follow-up after surgery showed no recurrence or evidence of systemic involvement. This clinical report highlights the importance of considering the synchronous occurrence of a carcinoma underlying an isolated parotid gland mass in the context of IgG4-RS, especially if there is no response to prior steroid medication.

Long-Term Outcomes of Tamoxifen Citrate Therapy and Histo- and Immunopathological Properties in Riedel Thyroiditis

BACKGROUND

Riedel thyroiditis (RT) is a rare form of thyroiditis; thus, data about the disease course and treatment options are limited. Therefore, we aimed to assess the clinical, serological, radiological, and histopathological features, as well as short- and long-term follow-up of RT patients under glucocorticoid (GC) and tamoxifen citrate (TMX). Parameters related to IgG4-related diseases (IgG4-RD) were also investigated.

METHODS

Eight patients with RT diagnosed between 2000 and 2019 were enrolled. Data were collected in a retrospective and prospective manner. The diagnosis was confirmed with histopathological features in all patients. Results of the treatment with GCs on short- to mid-term, followed by TMX in the long term, were evaluated.

RESULTS

The mean age at diagnosis was 40.5 ± 6.8 years; female predominance was observed (F/M:7/1). Parameters related to IgG4-RD, like increase in IgG4 serum levels, total plasmablast counts, and IgG4+ plasmablasts, were negative in most of our patients in both active and inactive states of the disease. Likewise, an increased ratio of IgG4/IgG-positive plasma cells >40% could only be observed in 2 cases. GCs followed by TMX were given to the patients with an over-all median follow-up time of 67 (8-216) months. All the patients considerably improved clinically and had a reduction in the size of the mass lesion on GCs, followed by TMX therapy. None of the patients had a recurrence under TMX therapy for a median period of 18.5 (7-96) months.

CONCLUSION

Even though RT is suggested to be a member of IgG4-RD, serologic or histological evidence of IgG4 elevation or positivity is only useful for diagnosis and follow-up of RT. The diagnosis should be based on clinical and radiological evidence and confirmed by histopathology. GCs are effective for initial treatment, and TMX is a successful and safe therapeutic option for long-term maintenance therapy.

Systemic IgG4-Related Disease Masquerading as Cholangiocarcinoma: A Case Report Underscoring the Importance of Medical History

BACKGROUND Immunoglobulin (Ig) G4-related disease is a rare disease of unknown pathophysiology, which can affect multiple organs leading to tissue fibrosis and organ failure. The present case report describes a patient with systemic IgG4-related disease (IgG4-RD) that occurred over a 1-year period and affected multiple organs at different times. Imaging studies, interventional procedures, changes in laboratory parameters, and histopathology demonstrate the novel and known aspects of this disease before and during prednisolone monotherapy and in combination with azathioprine. CASE REPORT A 64-year-old man presented with weight loss and painless jaundice, which was highly suspicious for cholangiocarcinoma. A thorough medical history together with laboratory tests, imaging procedures, and endoscopic interventions confirmed that surgery was not needed and led to the final diagnosis of histologically-confirmed, IgG4-related sclerosing cholangitis and autoimmune pancreatitis type 1. Other typical organ manifestations of systemic IgG4-RD were diagnosed through a thorough medical review, which led to immunohistochemical reevaluation of past surgical specimens. Besides the IgG4-related organ manifestations, which can include periorbital xanthelasmas, our patient developed a pulmonary adenocarcinoma 6 years after the initial clinical onset of IgG4-RD. After immunosuppressive treatment with prednisolone alone and subsequently in combination with azathioprine, the patient's IgG4-RD resolved. CONCLUSIONS Interdisciplinary collaboration is required to diagnose IgG4-RD that involves multiple organs. Patient medical history remains crucial for diagnosis and attention should be paid to avoiding unnecessary surgery. Tumors (lung adenocarcinomas) and xanthelasmas can develop because of IgG4-RD. Glucocorticoids and additional azathioprine may be advisable for maintenance treatment.

Immunoglobulin G4-related periodontitis: case report and review of the literature

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a chronic inflammatory systemic disease of unknown etiology that can affect one or multiple organs. The disease can mimic many infectious and inflammatory diseases, mainly causing organ enlargement or hyperplasia. Its diagnosis primarily relies on clinical, serologic, and histological features (lymphoplasmacytic infiltrates, storiform fibrosis, and obliterative phlebitis of IgG4 + plasma cells). Here, we report a rare case of IgG4-related periodontitis, and review the relevant literatures.

CASE PRESENTATION

A 38-year-old Chinese man visited the Department of Periodontics with gingival enlargement, loose teeth, and tooth loss. The patient had very poor oral hygiene and a large amount of calculus. Gingivae were edematous with deep periodontal pockets and attachment loss. Panoramic radiography showed alveolar bone loss. Serologic examination showed that IgG was 23.70 g/L and IgG4 concentration was 2.800 g/L. There was significant lymphoplasmacytic infiltration, a storiform pattern of fibrosis, and mitotic figures with hematoxylin and eosin staining; immunohistochemical staining showed 10 scattered IgG4-positive plasma cells in a high-power field. The patient was diagnosed as IgG4-related periodontitis. He received a course of corticosteroids with periodontal therapy, and the enlargement was significantly improved without recurrence.

CONCLUSION

IgG4-RD in the oral and maxillofacial region mainly involves salivary glands, but this rare case was characterized by enlarged gingivae. The differential diagnosis of IgG4-RD should be based on the clinical features and serologic (IgG4) and histopathological examinations. Corticosteroid therapy is effective for most IgG4-RD patients. Taken together, we hope this case report and the literature review can help dentists to improve their understanding of the IgG4-RD.

IgG4-related disease: an atypical presentation of steroid-responsive renal mass

IgG₄-related disease (IgG₄-RD) is a systemic fibroinflammatory disease characterised by dense lymphoplasmacytic infiltration rich in IgG₄-positive plasma cells, storiform fibrosis and obliterative phlebitis. Serum IgG₄ levels are typically elevated but half of the patients had normal serum IgG₄ levels. IgG₄-RD represents a spectrum of diseases that involve various organs such as the pancreas, liver, kidneys, and salivary glands often manifesting as diffuse organ enlargement or a mass-like lesion mimicking cancer. An increased incidence of malignancy among patients with IgG₄-RD has been reported. Thus, differentiating malignancy from IgG₄-RD manifestation is important as the treatment differs. Glucocorticoids are considered first-line therapy and should be started early to prevent fibrosis. Patients usually have an excellent clinical response to steroids, and poor steroid response is indicative of an alternative diagnoses such as malignancy. This case report describes a case of IgG₄-RD with renal mass in a young man that resolved with glucocorticoid therapy alone.

Experience from the first UK inter-regional specialist multidisciplinary meeting in the diagnosis and management of IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a complex multisystem fibro-inflammatory disorder, requiring diagnostic differentiation from malignancy and other immune-mediated conditions, and careful management to minimise glucocorticoid-induced toxicity and prevent progressive organ dysfunction. We describe the experience of the first inter-regional specialist IgG4-RD multidisciplinary team meeting (MDM) incorporating a broad range of generalists and specialists, held 6-weekly via web-link between Oxford University Hospitals NHS Foundation Trust and University College London Hospitals NHS Foundation Trust. Over 3 years, there were 206 discussions on 156 patients. Of these, 97 (62%) were considered to have definite or possible IgG4-RD; 67% had multi-organ involvement and 23% had a normal serum IgG4. The average number of specialist opinions sought prior to MDM was four per patient. Management was changed in the majority of patients (74%) with the treatment escalation recommended in 61 cases, including 19 for rituximab. Challenges arose from delays and misdiagnosis, cross-specialty presentation and the management of sub-clinical disease. Our cross-discipline IgG4-RD MDM enabled important diagnostic and management decisions in this complex multisystem disorder, and can be used as a model for other centres in the UK.

[IgG4-Related Disease: A rare cause of severe interstitial lung disease]

BACKGROUND

The intrathoracic manifestations of IgG4-related disease include a range of conditions and severity, and can on occasion cause acute respiratory failure as reported in the case described here.

OBSERVATION

A 69-year-old male former smoker, was admitted to our hospital with dyspnea, fever, cough, fatigue, and a 3-month history of weight loss. He received high flow oxygen therapy and non-invasive ventilation for severe respiratory failure. Chest computed tomography revealed multifocal condensations and ground glass opacities, accompanied by thickening of the perilymphatic interstitium, mediastinal lymphadenopathy and bilateral pleural effusion. Elevated serum concentrations of IgG4 suggested an IgG4-Related Disease. He developed renal failure and underwent a renal biopsy. Histopathological analysis of which supported the diagnosis by showing dense lymphocytic infiltrate with a count of IgG4+ cells/hpf higher than 60, and storiform fibrosis - a swirling, "cartwheel" pattern of fibrosis which may have a patchy distribution. The patient responded well to steroid therapy.

CONCLUSION

Although respiratory symptoms are usually mild in IgG4-relatd disease, thoracic features can evolve into acute respiratory failure with few extra thoracic manifestations.

Debulking Surgery Combined with Low-Dose Oral Prednisolone and Azathioprine for Intractable IgG4-Related Orbital Disease: A Case Report

A case of intractable IgG4-related orbital disease (IgG4-ROD) was successfully treated by debulking surgery combined with low-dose prednisolone and azathioprine as maintenance therapy. A 64-year-old man visited our clinic with progressive bilateral upper eyelid swelling and right eye fullness of a year’s duration. He was previously treated with systemic corticosteroids for the IgG4-ROD and experienced a partial clinical response but relapsed upon prednisolone cessation. The patient underwent debulking surgery of the right lacrimal gland and right upper eyelid. His post-operative medication was oral prednisolone (5 mg) every other day and 50 mg azathioprine per day. The patient’s right eye remained asymptomatic during the 18 months of follow-up. Debulking surgery combined with low-dose prednisolone and azathioprine, as a maintenance therapy, is an effective and alternative treatment for the long-term control of intractable IgG4-ROD.

IgG4 immunohistochemistry in Riedel's thyroiditis and the recommended criteria for diagnosis: A case series and literature review

OBJECTIVE

Riedel's thyroiditis (RT) is a very rare chronic fibrosing thyroiditis that is often associated with multifocal fibrosclerosis. Although the relationship of RT and IgG4-related disease (IgG4-RD) has been suggested, the expression of IgG and IgG4 in thyroid tissues of patients with RT has seldom been studied.

DESIGN

A case series and literature review.

PATIENTS AND MEASUREMENTS

We searched our hospital's pathology database and identified five cases of RT between 2000 and 2019. The expression levels of IgG4 and IgG in thyroid tissues were detected by immunohistochemistry. We also performed a literature search of the electronic databases PubMed/MEDLINE, Web of Science and China National Knowledge Internet (CNKI). Eight papers were included in this study.

RESULTS

According to immunohistochemistry, the numbers of IgG4+ plasma cells per high-power field (HPF) of the five RT patients at our hospital were 80, 8, 50, 10 and 22, and the respective IgG4+/IgG+ ratios were 76%, 80%, 43%, 19% and 28%. In the literature, 15 RT patients with confirmed IgG4 and IgG immunohistochemical findings were identified. Only seven of them fulfilled the IgG4-RD diagnostic criteria in terms of immunohistochemistry (IgG4+ > 10/HPF, IgG4+/IgG+ > 40%). In order to ensure that most RT cases can meet the IgG4 immunohistochemical criteria, an organ-specific cut-off value (≥10 IgG4+ plasma cells/HPF and ≥ an IgG4+/IgG ratio of 20%) was finally selected in our study.

CONCLUSION

Our findings of IgG4 expression in patients with RT suggest that a cut-off of 10 IgG4+ plasma cells/HPF and an IgG4+/IgG ratio of 20% are more suitable diagnostic criteria for RT in IgG4-RD.

Immunoglobulin G4-Hepatopathy with Acute Hepatitis-Like Onset and Marked Centrilobular Necrosis: Clinicopathologically Unique Pattern of Hepatic Injury Related to Immunoglobulin G4-Related Disease

A 69-year-old man presented with jaundice and appetite loss. Blood analyses showed elevated aminotransferase levels, hyperbilirubinemia, positivity for antinuclear antibody, elevated immunoglobulin (Ig) G4 levels, and negativity for hepatitis virus markers. Additionally, computed tomography revealed a focal enlargement of the pancreatic body and enhancement of the peripheral bile ducts. Liver biopsy showed interface hepatitis, supporting a clinical diagnosis of autoimmune hepatitis (AIH). Immunohistochemistry revealed that IgG4-bearing plasma cells accounted for more than 60% of the IgG-bearing plasma cells in the portal area. Then, we started oral prednisolone therapy. After tapering, serum transaminase levels became elevated again, and we had to adjust the dose. Azathioprine maintenance therapy was necessary to prevent relapse. We herein report a case of IgG4-hepatopathy with a clinical course similar to that of AIH with acute onset.

Inflammatory pseudotumor and myofibroblastic inflammatory tumor. Diagnostic criteria and prognostic differences

INTRODUCTION

Inflammatory pseudotumor (IPT) and inflammatory myofibroblastic tumor (IMT) are two very rare entities that were formerly included in the same category; however, today they are considered two different diseases due to the neoplastic origin of the IMT. Our objective is to share our experience in the management of these two types of tumors that we must take into account in the differential diagnosis of pulmonary masses or nodules.

METHODS

Thirteen patients with a pathological diagnosis of IPT and IMT who underwent surgery between 2008 and 2019 were retrospectively studied. We recorded the pre and postoperative information of each one, as well as the survival analysis.

RESULTS

Of the 13 patients, 8 were men and 5 women. The mean age of presentation was 53,5 years. An atypical segmentectomy was performed in 6 patients; a lobectomy was necessary in 6 and a pneumonectomy in 1 case. In all cases a complete resection was achieved. Diagnosis was possible thanks to histology, immunohistochemical (IHQ) and fluorescent in situ hybridization (FISH) techniques determining the expression of IgG4 and the rearrangement of ALK, respectively. After a median follow up of 49 months, we didńt find any loco-regional or distant recurrence in the patients studied.

CONCLUSION

IPT and IMT are rare tumors with a very good prognostic. The diagnosis of both entities is based mainly on specific anatomopathological techniques. Surgery has, in most cases, both a diagnostic and therapeutic role.

IgG4-Related Disease With Tuberculosis: A Case Report and Retrospective Review of Patients in a Single Center

Background

IgG4-related disease (IgG4-RD) is a recently recognized systemic fibro-inflammatory disease of unknown cause involving many organs including pancreas, salivary glands, and lymph nodes. Chronic tuberculosis (TB) infection has been reported in IgG4-RD, but the prevalence of TB infection has not been evaluated in IgG4-RD.

Methods

Characterization of a patient with IgG4-RD by physical examination, laboratory tests, magnetic resonance imaging (MRI) and histological examination. TB infection was evaluated by medical history, radiological examinations, sputum examinations, tubercular skin test (TST) and interferon gamma (IFN-γ) release assay test (IGRA). Medical records of IgG4-RD patients were reviewed in our institute from February 2015 to September 2020 to explore the prevalence of TB infection in IgG4-RD.

Results

We described a 40-year-old Chinese man presented with headache and diplopia. Physical examination revealed bitemporal hemianopsia and limited abduction of both eyes. MRI revealed uniformly enhancing mass overlying clivus with dural tail sign. Laboratory data revealed elevation of IgG4 (1.9g/L), and TB-IGRA demonstrated significantly elevated IFN-γ (414.21 pg/ml). The clivus lesion was subtotally removed and IgG4 was strongly positive on immunohistochemical staining. The diagnosis of IgG4-RD was established, and the patient received treatment of corticosteroids, methotrexate, and cyclophosphamide with isoniazid prophylaxis. Consequently, the mass shrank remarkably within 3 months. A similar concurrence of TB disease or latent TB infection (LTBI) and IgG4-RD was present in 17/47 (36.2%) patients in our institute.

Conclusion

High frequency of TB/LTBI presented in patients with IgG4-RD. Patients with IgG4-RD and LTBI should be closely monitored for resurgence of TB. Whether TB represents a risk for IgG4-RD should be further investigated in prospective cohort.

IgG4-related disease with multiorgan involvement: a case-based review

IgG4-related disease (IgG4-RD) is an immune-mediated multi-organ inflammatory disorder caused by tissue infiltration of lymphocytes with IgG4-secreting plasma cells. Herein, we discuss a case of a patient with IgG4-RD who had involvement of multiple organs: the kidneys, lymph nodes, bone marrow (biopsy performed), lungs, liver, and small intestine (imaging abnormalities). Although several case reports and series of IgG4-RD involving different organ involvement are in the literature, our patient has extensive simultaneous multi-organ involvement. We utilized the four domains (serologic, pathologic, radiologic, and pathologic) as discussed in the new 2019 ACR/EULAR classification criteria to provide a useful framework in considering an alternative tool for IgG4-RD in multi-organ involvement, where biopsy is more invasive and not always accessible. We highlight the findings of each organ involved that increase the likelihood that the patient has IgG4-RD. In our patient, the IgG4-RD classification criteria was fulfilled with total points adding up to 48. Our case meets the classification criteria for IgG4-RD, since at least one organ is involved to meet entry criteria (biopsy proven), no exclusion criteria are present, and the total points are ≥ 20. When such extensive involvement of IgG4-RD occurs, early diagnosis and treatment are recommended to avoid irreversible organ damage and better outcomes.

IgG4-Related Disease: A Retrospective Chinese Study of Features and Treatment Response of 98 Patients Including 4 Rare Cases

The features and treatment of 98 Chinese patients with immunoglobulin G4 (IgG4)-related disease (IgG4-RD) referred to a single tertiary referring centre were reviewed. Patients diagnosed with IgG4-RD according to the comprehensive diagnostic criteria (CDC) were included in the retrospective study from May 2012 to March 2019. We collected data on clinical, laboratory, imaging, histological features and treatment. Totally, 98 patients with IgG4-RD were enrolled. The common clinical manifestations included abdominal pain, salivary gland swelling and lymphadenopathy. 51% of the patients had multiple organs involvement. Lymph nodes, pancreas and salivary glands were most commonly involved. Four rare sites including ulna, cerebellum, scalp, and mammary gland were found. The serum IgG4 level was increased by 85.7%. The serum IgG4 level was positively correlated with the number of involved organs, IgG and IgG4/IgG. Low C3 and C4 levels were observed in 37.5% and 12.2% patients respectively, and all patients with kidney involvement had hypocomplementemia. A total of 54 patients underwent tissue biopsies, and 55.6%, 31.5% and 11.1% cases were diagnosed as definite, probable and possible IgG4-RD, respectively. Eighty-eight patients received glucocorticoids (GCs) therapy. Five patients underwent radical surgery to remove the lesion. 73% of them presented a complete or partial remission. IgG4-RD is a systemic fibroinflammatory disease with involvement of multiple organs throughout the body including some rare sites. Most IgG4-RD patients had increased serum IgG4 levels and patients with kidney involvement showed hypocomplementemia. GCs therapy is effective. More research is needed to provide a more reliable basis for the diagnosis and treatment of patients.

Atypical presentation of immunoglobulin G4-related disease as subglottic stenosis: a case-based review

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory pathology that has been reported to affect principally the retroperitoneum, hepatobiliary system, salivary glands, orbital structures or lymph nodes. However, IgG4-RD with laryngeal involvement is a very rare entity. Our aims were to describe a case of subglottic stenosis as first and only manifestation of IgG4-RD and review the literature. A patient with IgG4-RD affecting the larynx that presented as subglottic stenosis is described. A MEDLINE database search of IgG4-RD cases with laryngopharyngeal manifestations was also conducted. A 30-year-old Caucasian woman was referred to a tertiary care hospital for dyspnea on exertion, which had been increasing for the last 4 months. Medical and surgical procedures revealed a subglottic stenosis, with a histological finding of IgG4 positive plasma cell infiltration. There was no evidence of other organ involvement. She was successfully treated with oral glucocorticoids and rituximab infusions. Glucocorticoids were rapidly tapered and the rituximab regimen was optimized, with no evidence of relapses. In the literature review, we found a total of 12 reported cases with laryngopharyngeal involvement, two of them with subglottic stenosis. IgG4-RD of the larynx is rare but should be considered after excluding more common disorders.

Renal Involvement in IgG4-Related Disease: From Sunlight to Twilight

IgG4-Related Disease (IgG4-RD) is a fibroinflammatory condition characterized by a typical histopathological pattern (dense lymphoplasmacytic infiltrate with prevalent IgG4+ plasma cells and storiform fibrosis), which may involve the kidney both directly (IgG4-related kidney disease, IgG4-RKD) or indirectly, as a consequence of post-renal ureteral obstruction due to retroperitoneal fibrosis (IgG4-RD RF). The most frequent presentation of IgG4-RKD is IgG4-related tubulointerstitial nephritis (TIN), but a glomerular disease can be present, in most of the cases a membranous nephropathy. Albeit steroid-responsive, in some cases renal manifestations may lead to progressive and permanent organ damage. In this review we describe four clinical cases representative of typical and less typical renal manifestations of IgG4-RD, emphasizing a potential, subclinical, early involvement of the kidney in the disease.

Emerging therapy options for IgG4-related disease

INTRODUCTION

Awareness of IgG4-related disease (IgG4-RD) is increasing worldwide and specialists are now familiar with most of its clinical manifestations and mimickers. IgG4-RD promptly responds to glucocorticoids and repeated courses are typically used to induce and maintain remission because the disease relapses in most patients. If left untreated, it can lead to organ dysfunction, organ failure and death. Advancement in our understanding of IgG4-RD pathogenesis is leading to the identification of novel therapeutic targets and emerging treatments are now setting the stage for personalized therapies for the future.

AREAS COVERED

This review focuses on emerging treatment options for IgG4-RD based on our advancing understanding of disease pathophysiology. Research was performed in the English literature on Pubmed and clinicaltrials.gov databases.

EXPERT OPINION

Glucocorticoids remain the first-line induction treatment for the multi-organ manifestations of IgG4-RD. Alternative immunosuppressive agents for maintaining remission are warranted in order to avoid long-term steroid toxicity, and to offer a more mechanistic and personalized therapeutic strategy. Targeting B and T-lymphocyte activation represents the most promising approach, but randomized controlled trials are eagerly awaited to confirm positive preliminary experiences reported in case series and small cohort studies.

Punctate Purpura Complicated with Immunoglobulin G4-related Disease

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition affecting multiple organs; however, the involvement of skin lesions is rare. We herein report a 65-year-old man who presented with pruritic punctate purpura on both legs and elevated liver enzyme levels. Computed tomography showed enlargement of the pancreas and thickening of the bile duct wall. Magnetic resonance cholangiopancreatography showed diffuse irregular constriction of the main pancreatic duct, stricture of the lower common bile duct, and dilation after confluent stricture. A histopathologic examination of the pancreas and his enlarged salivary gland showed infiltration of IgG4-positive plasma cells. Ultimately, the patient was diagnosed with IgG4-RD.

Challenges in Medicine: The Odyssey of a Patient with Isolated IgG4-Related Eosinophilic Angiocentric Fibrosis Presenting as a Locally Destructive Sinonasal Mass

Eosinophilic angiocentric fibrosis (EAF) is an exceeding rare clinical entity and is considered a part of the spectrum of IgG4-related disease (IgG4RD). We hereby present such an unusual case of a 60-year-old female who presented to us with recurrent sinonasal mass, after a decade long haul of multiple clinical evaluations, biopsies, and debulking surgery without a definitive diagnosis. Over this period, the mass eroded through the ethmoid cells along with nasal septal destruction leading to saddle nose deformity, extended superiorly through the cribriform plates to right frontal lobe, and compressed the optic nerve leading to visual loss. Although initial biopsy was negative, repeat biopsy was performed owing to high clinical suspicion due to all the classic histopathological findings compatible with the diagnosis of eosinophilic angiocentric fibrosis IgG4-related disease (EAF-IgG4RD). Steroids are the recommended first-line therapy; however, our case was resistant to steroids needing rituximab to halt the disease progression. Our case interestingly also had T-cell clonality and isolated isocitrate dehydrogenase 2 enzyme mutation on next-generation sequencing, suggesting a possible role of novel molecular-targeted therapies in this rare disease. This case highlights the clinical challenges physicians face towards diagnosing and treating EAF-IgG4RD, emphasizing the need for high clinical suspicion and the possible role of targeted therapies for this rare disease.

An enigmatic case of IgG4-related nephropathy and an updated review of the literature

IgG4-related disease (IgG4-RD) is still an underestimated disorder which affects multiple organs, and its recognition as a distinct clinical disease has been only proved in the recent decades. The renal involvement has been documented in approximately 15% of patients with IgG4-RD, and the typical manifestation is a tubulo-interstitial nephritis. The main histological findings in IgG4-RD are typically a dense tissue infiltration of IgG4-positive plasma cells, storiform fibrosis, obliterative phlebitis, and frequently elevated IgG4 serum levels. Herein we report our atypical and peculiar clinical presentation of an IgG4-related nephropathy (IgG4-RN) and the remarkable response to rituximab (RTX) treatment at the renal imaging with computerized tomography assessment. The current nephrological evidences support the renal function recovery after steroids or steroids plus RTX therapy, even if the renal imaging data are not always shown. In a complex and enigmatic clinical scenario such as the IgG4-RN, both the renal biopsy and the renal imaging before and after the immunosuppressive therapy become mandatory tools to thoroughly define the diagnosis, the management and the response to the immunological therapy.

Histopathological findings in the landscape of IgG4-related pathology in patients with pituitary dysfunction: Review of six cases

IgG4-related hypophysitis (IgG4-RH) is increasingly being reported as an isolated entity or, less frequently, as a manifestation of a multiorgan IgG4-related disease (IgG4-RD), in which typical histopathology is a cornerstone for the diagnosis. We aimed to describe the histopathological changes in the surgical specimens from patients with clinical signs of pituitary disease that fulfilled the current diagnostic criteria for IgG4-RH. Histopathological features were correlated with clinical and radiological findings. Of 19 patients with pituitary dysfunction and inflammatory changes in the surgical pituitary specimen operated on during 2011-2019, we identified five patients with typical IgG4-related pathology (lymphoplasmacytic infiltration with more than 10 IgG4-positive plasma cells per one high power microscopic field, representing at least 40% of all plasma cells and at least focal storiform fibrosis). One patient with diabetes insipidus and pachymeningitis with IgG4-related changes in a biopsy from the dura was also included. Additional histopathological changes that typically are not part of the IgG4-RH were observed: Rathke's cleft cyst in four and granulomatous changes in two patients. One patient had an elevated serum IgG4 level and systemic manifestations that could be associated with the systemic IgG4-RD. Our findings indicate that pure IgG4-RH is uncommon. All patients with pituitary dysfunction, beyond typical IgG4-related pathology, had other pathological findings that could trigger the secondary IgG4-response. Both primary pathology and secondary IgG4-related features should be reported in patients with pituitary dysfunction because their co-occurrence may cause atypical clinical and imaging features, and unexpected response to surgical and pharmacological treatment. The current criteria for the diagnosis of IgG4-RH can lead to overdiagnosis of IgG4-RH if additional pathological changes are not taken into consideration. The classification criteria of IgG4-RD proposed by the American College of Rheumatology/European League Against Rheumatism could help classify patients more properly as IgG4-RH if applied to the pituitary gland.

IgG4-related disease: a great mimicker of lung cancer

IgG4-related disease is a rheumatological disorder, affecting multiple organ systems, and displaying dense lymphoplasmacytic inflammatory infiltrate and storiform fibrosis on histology. The pulmonary manifestations of IgG4-related disease are varied. Most commonly, bronchovascular consolidation and perilymphatic parenchymal thickening occur. IgG4-related disease can present as a solitary parenchymal mass and is often mistaken for a primary pulmonary or haematological malignancy. This report presents a case of IgG4-related disease in a patient with 6 months reported haemoptysis symptomatology and CT findings of perihilar lymphadenopathy, multiple pulmonary parenchymal nodules and a single parenchymal mass. Clinician cognisance of the histopathological presentation of IgG4-disease is important. It should be considered as a differential in patients for which investigations have ruled out malignancy, as it is responsive to glucocorticoids in the majority of cases.

IgG4-related disease and ANCA positive vasculitis in childhood: a case-based review

Autoimmune pancreatitis (AIP) type 1 is an IgG4-related disease (IgG4-RD), characterized by inflammatory pseudotumors and histologically by dense lymphoplasmacytic infiltrates rich in IgG4 positive plasma cells, storiform fibrosis, and obliterative phlebitis. Although quite rare, IgG4-RD was found to be associated with medium or small vessel vasculitides. A new overlap syndrome between IgG4-RD and ANCA-associated vasculitis (AAV) has recently been described in the adult population. Here we present a 16-year-old adolescent girl admitted with abdominal pain, episcleritis, palpable purpura, salivary gland enlargement, and bloody diarrhea. Laboratory investigations revealed findings of glomerulonephritis. Abdominal imaging surprisingly revealed a focal mass in the pancreatic tail, while the c-ANCA level was found to be quite high as well as serum IgG4 level. Biopsy of the pancreatic mass showed lymphoplasmacytic IgG4 positive cells infiltrating the pancreas with storiform fibrosis compatible with IgG4-related AIP. The renal biopsy that was done simultaneously showed necrotizing granulomatous vasculitis indicating AAV. Renal biopsy showed IgG4 positive plasma cells very rarely by immunohistochemical examination, which does not indicate any significance for IgG4-RD. Our diagnosis was IgG4-related AIP and AAV overlap syndrome, which has not been reported in the pediatric populations yet. IgG4-RD should be investigated in patients with ANCA-associated vasculitis who shows atypical organ involvement. We searched the Pubmed/Medline and Google Scholar databases to identify clinical findings, treatment, and outcome of the patients with IgG4-related AIP and AAV.

B cell targeted therapy for immunoglobulin G4-related disease

Glucocorticoids are the first-line drug for the remission induction therapy of immunoglobulin (Ig) G4-related disease. Achieving drug-free remission using glucocorticoids alone is difficult, however, and many patients require maintenance therapy with glucocorticoids and immunosuppressants. Studies have recently found that the number of peripheral memory B cells and plasmablasts is increased in IgG4-related disease and have indicated the efficacy of rituximab, which, in remission induction therapy, rapidly reduces serum IgG4 levels and has the tapering effect of glucocorticoids. Rituximab has been shown to reduce the risk of relapse more than oral immunosuppressants such as azathioprine. However, maintaining drug-free remission is difficult with a single course of rituximab alone, and many cases require maintenance therapy with rituximab. This article outlines the potential of B-cell targeted therapy, focusing on the efficacy, and safety of rituximab for IgG4-related disease.

IgG4 related disease

IgG4-related disease (ER-IgG4) is a recognised systemic disease. It was described after patients diagnosed with autoimmune pancreatitis showed signs of extra-pancreatic disease. The clinical manifestation of these patients is subacute and is manifested by the appearance of pseudotumoral lesions, or inflammatory or fibrous tumours. Sometimes it can be serious as in the case of patients with cholangitis or large vessel vasculitis. Diagnostic criteria include, among others, serum IgG4 elevation and/or histological parameters. The 18F-FDG-PET/CT is useful in the initial diagnosis, biopsy guidance as well as in the assessment of response to therapy. It usually responds to steroid therapy.

Efficacy and safety of rituximab biosimilar (CT-P10) in IgG4-related disease: an observational prospective open-label cohort study

OBJECTIVE

Rituximab is increasingly used in IgG4-related disease (IgG4-RD) but high costs limit its wide off-label administration. European and US regulatory agencies have recently approved rituximab biosimilars for the treatment of different rheumatologic and hematological conditions. No data are available, yet, on the efficacy and safety of rituximab biosimilars for the treatment of IgG4-RD. Scope of the present work is to evaluate the efficacy and safety of the rituximab biosimilar CT-P10 (RTX-B) in patients with IgG4-RD.

METHODS

Patients with active IgG4-RD, naïve to rituximab or switched from the originator (RTX-O) to the biosimilar were treated with RTX-B and prospectively followed-up for 18 months. Safety and efficacy were assessed at six months. Relapse rate was assessed at 18 months. Disease activity was assessed by means of the IgG4-RD Responder Index (IgG4-RD RI).

RESULTS

Thirty-eight patients were included in this study. Thirty-three patients (87%) were naïve to RTX. Five patients (13%) relapsed after RTX-O and were switched to RTX-B. After six months, 21 patients (60%) achieved disease remission. The median serum IgG4 concentration decreased from 1344 to 575 mg/L (p < 0.01), and the median IgG4-RD RI decreased from 7.5 to 0 (p < 0.01). B-cell depletion was observed in all patients. Eight patients (36%) relapsed within 18 months. Side effects related to RTX-B administration were observed in 14 patients (37%). These results are in line with our previous experience with RTX-O.

CONCLUSIONS

The (TruximaTM) rituximab biosimilar CT-P10 represents a safe and effective alternative to rituximab originator for the treatment of IgG4-RD.

Imaging of IgG4-Related Disease in the Head and Neck: A Systematic Review, Case Series, and Pathophysiology Update

This systematic review aims to clarify and comprehensively detail the sometimes variable published imaging features as well as the pathogenesis, clinical diagnostic criteria, and treatment options of IgG4-Related Diseases (IgG4-RD) in the head and neck to aid the radiologist in diagnosing relapse and new sites of disease. A literature search in PubMed and EMBASE for reported cases of IgG4-RD was performed in December 2019. Case reports or series of IgG4-RD in the head and neck in adults that included sufficient imaging and pathology findings were included. This yielded 50 reports. IgG4-RD locations included the orbits, thyroid, pituitary gland, paranasal sinuses, salivary and parotid glands, larynx, pharynx, cervical lymph nodes, meninges, and skull base. Most lesions demonstrated non-specific homogenous CT attenuation, diffuse enhancement, isointense/low T2 signal intensity, and low T1 signal intensity. 6 cases from our institution followed previously reported imaging patterns.

The enigmatic immunoglobulin G4-related disease and its varied cardiovascular manifestations

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disease characterised by multiorgan lymphoplasmacytic infiltration, obliterative phlebitis and storiform fibrosis. It can be associated with cardiovascular pathology. The objective of this narrative review is to summarise the published literature on cardiovascular manifestations of IgG4-RD and to provide a basis for diagnosis and management of the condition by the practising cardiologist.We propose the following categorisations of cardiovascular IgG4-RD: aortitis, medium-vessel arteritis, pulmonary vascular disease, phlebitis, valvulopathy, pericarditis, myocardial disease and antineutrophilic cytoplasmic antibody-associated vasculitis. We also review herein developments in radiological diagnosis and reported medical and surgical therapies. Cardiovascular lesions frequently require procedural and/or surgical interventions, such as aortic aneurysm repair and valve replacement. IgG4-RD of the cardiovascular system results in serious complications that can be missed if not evaluated aggressively. These are likely underdiagnosed, as clinical presentations frequently mimic cardiovascular disease due to more common aetiologies (myocardial infarction, abdominal aortic aneurysm and so on). While systemic corticosteroids are the mainstay of IgG4-RD treatment, biological and disease-modifying agents are becoming more widely used. Cardiologists should be aware of cardiovascular IgG4-RD as a differential diagnosis, and understand the roles of corticosteroids, disease-modifying agents and biologicals, as well as their integration with surgical approaches. There are several knowledge gaps, including diagnosis, risk factors, pathogenesis and appropriate management in Ig4-RD of the cardiovascular system. Areas lacking well-conducted randomized trials include safety of steroids in the setting of vascular aneurysms and the role of disease-modifying drugs and biological agents in patients with established cardiovascular complications of this multifaceted enigmatic disease.

IgG4-related disease manifesting as symptoms of appendicitis: Case report and literature review

Immunoglobulin G subclass 4 (IgG4)-related disease is a recently described fibroinflammatory condition. Reports of appendix involvement are extremely limited. A young man with abdominal pain and symptoms of acute appendicitis accompanied by the finding of an appendix-dependent tumor during surgery is presented. Histopathological study revealed lymphoplasmocytic infiltrate, storiform fibrosis and obliterative phlebitis. The number of IgG4-positive plasma cells was greater than 50 per high power field. Postsurgical steroid treatment and radiological findings are also described.

Visual impairment in immunoglobulin G4-related disease: A case report

The present study reports on the case of a 50-year-old male with sinusitis, diplopia, secretory otitis media and skin eczema for >14 years. The patient presented with visual impairment in both eyes and subxiphoid pain on admission to the First Affiliated Hospital of China Medical University (Shenyang, China). Orbital CT revealed a slightly thickened left inferior rectus muscle. Due to a periocular mass, enlarged lymph nodes, elevated serum immunoglobulin G4 (IgG4) levels and enriched IgG4-positive plasma cells in the lymph nodes, the diagnosis of IgG4-related disease (IgG4-RD), possibly involving at least 10 organs, was established. Following treatment with methylprednisolone, the serum IgG4 levels decreased to normal and binocular vision returned to normal. Unlike previously reported cases, the present case exhibited no swollen masses around the optic nerve. The purpose of the present case report was to improve the understanding of IgG4-RD.

Not All Küttner Tumors Are IgG4-Related Disease (IgG4-RD)

Küttner tumor is an uncommon cause of salivary gland enlargement that most frequently affects the submandibular gland. More recently it has been considered a manifestation of IgG4-related disease (IgG4-RD) and synonymous with chronic sclerosing sialadenitis (CSS). We present a series of cases to emphasize this clinical entity as a disease pattern and presentation that is separate from IgG4-RD. Retrospective case series of 3 patients with unilateral salivary gland enlargement, or "Küttner tumor," histologically classified as "chronic sclerosing sialadenitis," The clinical history, radiology reports, laboratory studies, and pathology slides were reviewed for each case. Radiology showed discrete unilateral mass-like lesions in all three cases. Immunohistochemistry showed reduced tissue IgG4-positive plasma cells in two cases and increased numbers in one case, but insufficient to diagnose IgG4-RD. Storiform fibrosis was not seen in all cases and did not coincide with increased IgG4-positive plasma cells. A systemic workup, including serum IgG4 levels in two cases, was normal. A brief review of the literature on the spectrum of salivary gland involvement by IgG4-RD is presented. Küttner tumor is not necessarily the same as chronic sclerosing sialadenitis and is not always associated with IgG4-related disease. This report includes the second documented case of Küttner tumor of the sublingual gland.

Asymptomatic pleural thickening with effusion as the only manifestation of IgG4-related disease

Immunoglobulin G4 (IgG4)-related disease is a systemic fibroinflammatory disorder that can affect almost any tissue. Isolated IgG4 pleural disease is a rare manifestation and, when present, is usually described in patients presenting with dyspnoea. We present a case of asymptomatic isolated IgG4 pleural effusion and highlight that IgG4-related disease should be remembered as a differential diagnosis in patients with pleural effusion and pleural thickening, even if asymptomatic and without any other organ involvement.

Camacho M, Cunha B, Alkatan H, Xavier N. Plasma cell IgG4 positivity in orbital biopsies of non-IgG4-related conditions

The IgG4-related disease (IgG4-RD) is a systemic condition defined as a fibro-inflammatory disorder, characterized by the occurrence of tumor-like lesions in multiple organs including the eye adnexa. The main diagnostic criterion is based on histopathological findings, especially on the IgG4⁺/IgG⁺ plasma cell ratio. In this article, we reviewed the literature of non-IgG4-RD orbital conditions with IgG4 positivity. There were 20 reports of inflammatory non-IgG4-RD orbital lesions and 14 reports of orbital lymphoid proliferations with significant IgG4 positivity. The role of plasma cells IgG4 in the pathogenesis of non-IgG4-RD is not clear. Considering the large spectrum of diseases caused by a variety of different etiopathogenic mechanisms, we think that the common denominator of IgG4⁺ in these conditions might be related to the peculiar properties of down regulation of immune response of the IgG4 and not to a specific link to IgG4-RD.

[SIGNIFICANCE OF IgG4 IN IDIOPATHIC RETROPERITONEAL FIBROSIS]

(Objective)Retroperitoneal fibrosis is largely divided into the idiopathic and secondary types. Some idiopathic cases include IgG4-related diseases, which are often similar to malignant diseases, such as lymphoma and sarcoma. The diagnostic criteria for IgG4-related disease are used and pathologic examination is necessary for a definitive diagnosis of IgG4-related retroperitoneal fibrosis. The first choice of treatment for IgG4-related retroperitoneal fibrosis is steroid administration, but no consensus has been established regarding its dose and tapering schedule. We investigated the significance of IgG4 in diagnosis and treatment of idiopathic retroperitoneal fibrosis. (Patients and methods)We examined 14 cases diagnosed as idiopathic retroperitoneal fibrosis between April 2013 and March 2019. Serum IgG4 was measured at the time of diagnosis in 13 cases, and changes over time in serum IgG4 before and after the induction of steroid therapy were measured in 6 cases. Computed tomography-guided biopsy was performed on 4 cases. (Results)Of all cases, 1 patient was diagnosed as IgG4-related retroperitoneal fibrosis and 5 patients were classified as possible group. Ten patients were administered steroid therapy. Percutaneous nephrostomy tube was placed in 3 patients and was removed in 2 of these patients after steroid therapy. The serum high levels of IgG4 were confirmed in all 4 patients who were classified into the possible group and who were treated with steroids. (Conclusion)Although histologic examination is necessary for the diagnosis of retroperitoneal fibrosis, tissue collection by open or laparoscopic surgery is highly invasive. CT-guided biopsy may be useful in high-risk cases, such as elderly patients on anticoagulation. After excluding other diseases in high-risk cases, response to empiric steroid therapy may be diagnostic. In the possible group, changes in serum IgG4 levels may reflect the disease condition and might be useful in determining the maintenance dose of steroids.

[Immunoglobulin G4-related disease in gastroenterology]

IgG4-related disease is a recently defined clinical entity that can manifest itself in any organ. The most common gastrointestinal manifestations are diseases of the pancreas (autoimmune pancreatitis type 1) and biliary tree (IgG4-associated cholangitis); involvement of liver parenchyma is uncommon and the affection of tubular organs is very rare. IgG4-related pancreatitis and cholangitis can mimic malignancies in their clinical presentation. Diagnosis is often difficult and requires careful evaluation of the combination of symptoms, serology and imaging findings, while adhering to the established diagnostic criteria. The first line of treatment is the administration of corticoids and the remission is achieved in the vast majority of patients. In case of contraindication, intolerance or failure of corticotherapy, patients should receive B cell depletion therapy (rituximab). Based on the available knowledge, monotherapy with other immunosuppressants is not considered to be sufficiently effective. Some patients may benefit from maintenance treatment to prevent relapse, which is otherwise common in both IgG4-related pancreatitis and cholangitis. Recognized IgG4-related disease has a good prognosis, but some patients develop irreversible fibrotic changes in the affected organ with consequent dysfunction; the possible association of the disease with a higher risk of malignancy has not yet been reliably elucidated.

TDP-43-specific Autoantibody Decline in Patients With Amyotrophic Lateral Sclerosis

OBJECTIVE

We hypothesize alterations in the quality and quantity of anti-43-kDa TAR DNA-binding protein (TDP-43) naturally occurring autoantibodies (NAbs) in patients with amyotrophic lateral sclerosis (ALS); therefore, we assessed relative binding properties of anti-TDP-43 NAbs composite in plasma from patients with ALS in comparison with healthy individuals.

METHODS

ELISA competition assay was used to explore the apparent avidity/affinity of anti-TDP-43 NAbs in plasma from 51 normal controls and 30 patients with ALS. Furthermore, the relative levels of anti-TDP-43 NAbs within the immunoglobulin (Ig) classes of IgG (isotype IgG1-4) and IgMs were measured using classical indirect ELISA. The occurring results were hereafter correlated with the measures of disease duration and disease progression.

RESULTS

High-avidity/affinity anti-TDP-43 NAbs levels were significantly reduced in plasma samples from patients with ALS. In addition, a significant decrease in relative levels of anti-TDP-43 IgG3 and IgM NAbs and a significant increase in anti-TDP-43 IgG4 NAbs were observed in ALS plasma vs controls. Furthermore, a decrease in global IgM and an increase in IgG4 levels were observed in ALS. These aberrations of humoral immunity correlated with disease duration, but did not correlate with ALS Functional Rating Scale-Revised scores.

CONCLUSIONS

Our results may suggest TDP-43-specific immune aberrations in patients with ALS. The skewed immune profiles observed in patients with ALS could indicate a deficiency in the clearance capacity and/or blocking of TDP-43 transmission and propagation. The decrease in levels of high affinity/avidity anti-TDP-43 NAbs and IgMs correlates with disease progression and may be disease predictors.

A clinical approach to hypertrophic pachymeningitis

IMPORTANCE

Hypertrophic pachymeningitis (HP) is a non-usual manifestation of rheumatologic, infectious, and neoplastic diseases. Etiological diagnosis is a challenge, but when made promptly it creates a window of opportunity for treatment, with the possibility of a total reversal of symptoms.

OBSERVATIONS

HP is an inflammatory process of the dura mater that can occur as a manifestation of sarcoidosis, granulomatosis with polyangiitis, and IgG4-related disease. The HP case evaluation is extensive and includes central nervous system imaging, cerebrospinal fluid analysis, serology, rheumatologic tests, and systemic survey for other manifestations sites. After systemic investigation, meningeal biopsy might be necessary. Etiology guides HP treatment, and autoimmune disorders are treated with corticosteroids alone or associated with an immunosuppressor.

CONCLUSION

HP is a manifestation of several diseases, and a precise etiological diagnosis is crucial because of the difference among treatments. An extensive investigation of patients with HP helps early diagnosis and correct treatment.

IgG4-related disease: Changing epidemiology and new thoughts on a multisystem disease

IgG4-related disease (IgG4-RD) represents an immune-mediated fibroinflammatory condition with peculiar histopathologic changes that can affect various organs. In 2012 its unified nomenclature was published, which allows to abandon other synonymous names. Up to now, only little is known about its epidemiology around the world. However, although it is generally considered a rare condition, the number of patients with IgG4-RD is increasing enormously. Likewise, the annual number of publications on this subject has increased progressively. The spectrum of clinical manifestations in IgG4-RD is highly variable, depending on the severity of the disease as well as the presence of organ(s) involvement. This review gives an overview on changing epidemiology of IgG4-RD focusing the attention on the large cohorts of patients published in the literature.

Pathology of IgG4-related sclerosing mastitis

Immunoglobulin G4-related sclerosing mastitis (IgG4-RM) is a recently recognised member of the IgG4-related disease (IgG4-RD) family, a multisystem fibroinflammatory condition that can affect any organ system. IgG4-RM is rare and predominantly occurs in middle-aged women. It may present with painless palpable mass and/or lymphadenopathy thereby mimicking breast cancer. Although there is an abundance of literature describing the clinicopathological characteristics of IgG4-RD in a variety of organs, data on IgG4-RM are limited due to its rarity. This review describes the manifestation of the disease in the breast based on reported cases, emphasising the clinicopathological features, pathophysiology, differential diagnosis, treatment and prognosis.

Long-term effects of intensive B cell depletion therapy in severe cases of IgG4-related disease with renal involvement

IgG4-related disease (IgG4-RD) is an immune-mediated disorder often showing elevated serum IgG4 concentrations, dense T and B lymphocyte infiltration, and IgG4-positive plasma cells and storiform fibrosis. We prospectively evaluated for 4 years 5 patients with histologically proven IgG4-RD of whom 3 had tubulointerstitial nephritis (TIN) and 2 had retroperitoneal fibrosis (RPF). They received an intensive B depletion therapy with rituximab. The estimated glomerular filtration rate of TIN patients after 1 year increased from 9 to 24 ml/min per 1.73 m2. IgG/IgG4 dropped from 3236/665 to 706/51 mg/dl, C3/C4 went up from 49/6 to 99/27 mg/dl, and the IgG4-RD responder index fell from 10 to 1. CD20+ B cells decreased from 8.7 to 0.5%. A striking drop in interstitial plasma cell infiltrate as well as normalization of IgG4/IgG-positive plasma cells was observed at repeat biopsy. Both clinical and immunological improvement persisted over a 4-year follow-up. Treating these patients who were affected by aggressive IgG4-RD with renal involvement in an effort to induce a prolonged B cells depletion with IgG4 and cytokine production decrease resulted in a considerable rise in eGFR, with IgG4-RD RI normalization and a noteworthy improvement in clinical and histological features. Furthermore, the TIN subgroup was shown not to need for any maintenance therapy.