Riedel's thyroiditis and multifocal fibrosclerosis are part of the IgG4-related systemic disease spectrum

IgG4-related diseases

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a fascinating condition recognised as a systemic disease in 2003 [1,2]. The first link between autoimmunity affecting the pancreas, elevated serum IgG4 concentrations and large numbers of IgG4-positive plasma cells in pancreatic tissue was described only 2 years earlier [3]. Since then, many diseases that have long been viewed organ-specific are now considered within the spectrum of IgG4-RD. Practically any organ can be affected, having in common a key pathological feature consisting in dense lymphocyte and plasma cell infiltrate rich in IgG4-positive plasma cells, storiform fibrosis and often an elevated serum IgG4 concentration. While good clinical response to steroid therapy is observed, immunosuppressive or B-cell depleting therapy can be required. It is important to distinguish the IgG4-RD from traditional organ-specific autoimmune disease to guide therapy.

Clinical features of a new disease concept, IgG4-related thyroiditis

OBJECTIVES

Immunoglobulin (Ig)G4-related disease is a recently proposed systemic disorder that includes autoimmune pancreatitis (AIP), Mikulicz's disease, and various other organ lesions. In the present retrospective study, we examined whether thyroid lesions should also be included in IgG4-related disease (Ig4-RD) under the new term IgG4-related thyroiditis.

METHOD

We enrolled 114 patients with Ig4-RD, including 92 patients with AIP, 15 patients with Mikulicz's disease, and seven patients with IgG4-related cholangitis, and analysed clinical findings, function, serum values of activity markers, computed tomography (CT) images, and histology of the thyroid gland.

RESULTS

Among the 22 patients (19%) in our cohort who were found to have hypothyroidism [thyroid stimulating hormone (TSH) > 4 mIU/L], 11 patients had clinical hypothyroidism [free thyroxine (FT4) < 1 ng/dL] and 11 patients had subclinical hypothyroidism (FT4 ≥ 1 ng/dL). Serum concentrations of IgG, IgG4, circulating immune complex (CIC), and β2-microglobulin (β2-MG) were significantly higher in the hypothyroidism group compared with the remaining 92 euthyroid patients, and serum C3 concentration was significantly lower. After prednisolone treatment, TSH values had decreased significantly (p = 0.005) in this group and FT4 values had increased significantly (p = 0.047). CT images showed that the thyroid glands of patients with clinical hypothyroidism had a significantly greater volume than those of the euthyroid and other groups. Pathological analysis of one resected thyroid gland disclosed a focused lesion with infiltration of lymphocytes and IgG4-bearing plasma cells and loss of thyroid follicles.

CONCLUSIONS

Thyroid lesions associated with hypothyroidism can be considered as a new disease termed IgG4-related thyroiditis. Awareness of this condition should lead to appropriate corticosteroid treatment that may prevent progression to a fibrous state.

Retroperitoneal fibrosis

Retroperitoneal fibrosis (RPF) is a condition characterized by the presence of inflammation and fibrosis in the retroperitoneal space, for which no standard diagnostic criteria exist. Historically, treatment has focused on relieving the obstruction with percutaneous or cystoscopic assisted placement of ureteral stents followed by more definitive resolution of ureteric obstruction with open or laparoscopic ureterolysis. However, over the past several years management has shifted from primarily a surgical approach to an immunosuppressive-based therapy aimed at modulation of the immune system. This review focuses on the recent advances in the classification, epidemiology, pathophysiology, pathology, imaging, and treatment of RPF.

Rethinking Ormond's disease: "idiopathic" retroperitoneal fibrosis in the era of IgG4-related disease

Idiopathic retroperitoneal fibrosis (RPF) is a periaortic sclerotic disease that encases adjacent retroperitoneal structures, particularly the ureters. A subset of idiopathic RPF cases can be associated with IgG4-related disease, but the frequency of this association is not clear. We selected 23 cases of idiopathic RPF and identified IgG4-related RPF cases based on the presence of IgG4+ plasma cells in the tissue, using an IgG4/IgG ratio cutoff of >40%. We then compared the IgG4-related RPF patients and the non-IgG4-related RPF patients in terms of both the presence of histopathologic features typical of IgG4-related disease and the simultaneous occurrence (or history) of other organ manifestations typical of IgG4-related disease. The IgG4-related RPF and non-IgG4-related RPF groups were also analyzed in terms of clinical, laboratory, and radiologic features and treatment review. We identified 13 cases of IgG4-related RPF (57% of the total cohort). The distinguishing features of IgG4-related RPF were histopathologic and extra-organ manifestations of IgG4-related disease. The IgG4-related RPF patients were statistically more likely than non-IgG4-related RPF patients to have retroperitoneal biopsies showing lymphoplasmacytic infiltrate (p = 0.006), storiform fibrosis (p = 0.006), or tissue eosinophilia (p = 0.0002). Demographics of the 2 groups, including a middle-aged, male predominance (mean age, 58 yr; 73% male), were similar. IgG4-related disease accounts for a substantial percentage of patients with "idiopathic" RPF. Histopathologic features such as storiform fibrosis, obliterative phlebitis, and tissue eosinophilia are critical to identifying this disease association. Extraretroperitoneal manifestations of IgG4-related disease are also often present among patients with IgG4-related RPF. Elevated IgG4/total IgG ratios in tissue biopsies are more useful than the number of IgG4+ plasma cells per high-power field in cases of RPF that are highly fibrotic.

IgG4-related disease of the head and neck

IgG4-related disease is an uncommon sclerosing and inflammatory mass-forming disease that may affect a single organ or be systemic. The prototypical example of the disease is type 1 autoimmune pancreatitis. After the pancreatobiliary system, the head and neck is the next most common site for involvement by IgG4-related disease. Here, we describe the clinicopathologic features of the head and neck involvement by this disease process with particular attention to involvement of the major salivary glands, the lacrimal glands and periorbital tissues, the upper aerodigestive tract, the thyroid gland, lymph nodes, the ear, and the skin and soft tissues.

IgG4-related disease: nomenclature, clinical features, and treatment

Concepts about IgG4-related disease (IgG4-RD) are now emerging swiftly. The condition has been identified in virtually every organ system, and its features are often excellent mimickers of malignancies, infections, and other immune-mediated disorders. Recommendations for nomenclature were proposed by the Organizing Committee of the 2011 International IgG4-related disease Symposium, and guidelines for the pathologic diagnosis of this condition have been published by an international group of experts. Experience with treatment regimens is growing. Glucocorticoids and B-cell depletion strategies both appear to be effective and are the subject of ongoing studies. This article reviews the current thought and understanding of this disease with regard to nomenclature, organ system involvement, and approaches to therapy.

Riedel's thyroiditis with increased IgG4 plasma cells: evidence for an underlying IgG4-related sclerosing disease?

BACKGROUND

Riedel's thyroiditis (RT) is a very rare chronic fibrosing disorder of unknown etiology that is often associated with multifocal fibrosclerosis (MFS). Immunoglobulin (Ig) G4-related sclerosing disease (IgG4-RSD), a new clinico-pathological entity also associated with MFS, is characterized by IgG4+ plasma cell infiltration and fibrosis in one or more organs. Although the association of RT and IgG4-RSD has been suggested, it has seldom been studied or reported. We report a classical case of RT with serological (IgG4 levels) and immunohistochemical (IgG and IgG4) assessment, in search of an underlying IgG4-RSD.

PATIENT

The patient was a 57-year-old woman who underwent a subtotal thyroidectomy for a long-standing goiter with a rapidly enlarging isthmic nodule.

RESULTS

Histopathological examination of the surgical specimen revealed all of the morphological features of RT and IgG4-RSD, including partial fibrosis of the thyroid gland with destruction of the thyroid follicular architecture; obliterative phlebitis; and a mixed infiltrate composed of lymphocytes, eosinophils, and plasma cells. The fibro-inflammatory process extended beyond the thyroid capsule into the surrounding tissues. Immunohistochemical examination revealed approximately 70 IgG4+ plasma cells per high power field (HPF) with an IgG4/IgG ratio of 35%. Although serum levels of IgG4 were normal (20 mg/dL), total IgG levels were slightly elevated (1370 mg/dL). There was no evidence of involvement of other organs at the time of RT diagnosis.

CONCLUSIONS

The morphological similarities between RT and IgG4-RSD suggest that these entities are closely related. Therefore, RT with increased IgG4+ plasma cells, with or without elevated IgG4 serum levels, may represent the first clinical manifestation of an underlying IgG4-RSD. However, due to the rarity of both conditions and the limited specificity and sensitivity of both IgG4 serum levels and IgG/IgG4 immunohistochemistry in the diagnosis of IgG4-RSD, further studies are needed to verify this hypothesis.

Consensus statement on the pathology of IgG4-related disease

IgG4-related disease is a newly recognized fibro-inflammatory condition characterized by several features: a tendency to form tumefactive lesions in multiple sites; a characteristic histopathological appearance; and-often but not always-elevated serum IgG4 concentrations. An international symposium on IgG4-related disease was held in Boston, MA, on 4-7 October 2011. The organizing committee comprising 35 IgG4-related disease experts from Japan, Korea, Hong Kong, the United Kingdom, Germany, Italy, Holland, Canada, and the United States, including the clinicians, pathologists, radiologists, and basic scientists. This group represents broad subspecialty expertise in pathology, rheumatology, gastroenterology, allergy, immunology, nephrology, pulmonary medicine, oncology, ophthalmology, and surgery. The histopathology of IgG4-related disease was a specific focus of the international symposium. The primary purpose of this statement is to provide practicing pathologists with a set of guidelines for the diagnosis of IgG4-related disease. The diagnosis of IgG4-related disease rests on the combined presence of the characteristic histopathological appearance and increased numbers of IgG4⁺ plasma cells. The critical histopathological features are a dense lymphoplasmacytic infiltrate, a storiform pattern of fibrosis, and obliterative phlebitis. We propose a terminology scheme for the diagnosis of IgG4-related disease that is based primarily on the morphological appearance on biopsy. Tissue IgG4 counts and IgG4:IgG ratios are secondary in importance. The guidelines proposed in this statement do not supplant careful clinicopathological correlation and sound clinical judgment. As the spectrum of this disease continues to expand, we advocate the use of strict criteria for accepting newly proposed entities or sites as components of the IgG4-related disease spectrum.

Distinct histopathological features of Hashimoto's thyroiditis with respect to IgG4-related disease

A form of Hashimoto's thyroiditis with lymphoplasmacytic sclerosing changes and increased numbers of IgG4-positive plasma cells has recently been reported in the literature. These histopathological features suggest that this subtype of Hashimoto's thyroiditis may be closely related to IgG4-related disease. Therefore, this unique form of IgG4-related Hashimoto's thyroiditis, which is referred to as IgG4 thyroiditis, has its own clinical, serological, and sonographic features that are distinct from those associated with non-IgG4 thyroiditis. IgG4 thyroiditis shares similarities with the well-known fibrous variant of Hashimoto's thyroiditis; however, the detailed histopathological features of IgG4 thyroiditis have not been well established. Based on immunostaining results, 105 patients with Hashimoto's thyroiditis were divided into an IgG4 thyroiditis group (n=28) and a non-IgG4 thyroiditis group (n=77). As in our previous reports, IgG4 thyroiditis was associated with a patient population of a younger age, a lower female-to-male ratio, rapid progression, higher levels of thyroid autoantibodies, subclinical hypothyroidism, and diffuse sonographic echogenicity. Histopathologically, this group revealed severe lymphoplasmacytic infiltration, dense stromal fibrosis, marked follicular cell degeneration, numerous micro-follicles, and notable giant cell/histiocyte infiltration. Importantly, the IgG4-related group did not completely overlap with fibrous variant of Hashimoto's thyroiditis. Four cases (14%) in the IgG4 thyroiditis group presented only mild fibrosis in the stroma, whereas 29 cases (38%) in the non-IgG4 thyroiditis group met the diagnostic criteria for fibrous variant of Hashimoto's thyroiditis. Furthermore, we observed three patterns of stromal fibrosis in Hashimoto's thyroiditis: interfollicular fibrosis, interlobular fibrosis, and scar fibrosis. The IgG4 thyroiditis group was significantly associated with the presence of predominant interfollicular fibrosis. In conclusion, IgG4 Hashimoto's thyroiditis presents histopathological features quite distinct from its non-IgG4 counterpart.

Are Classification Criteria for IgG4-RD Now Possible? The Concept of IgG4-Related Disease and Proposal of Comprehensive Diagnostic Criteria in Japan

Recent studies suggest simultaneous or metachronous lesions in multiorgans characterized by elevated serum levels of IgG4 and abundant infiltration of IgG4-positive plasma cells with various degrees of fibrosis. Two Japanese research committees for IgG4-RD, one from fibrosclerosis (Okazaki team) and the other from lymph proliferation (Umehara team) supported by the “Research Program for Intractable Disease” of the Ministry of Health, Labor, and Welfare of Japan, have agreed with the unified nomenclature as “IgG4-RD” and proposed the comprehensive diagnostic criteria (CDC) for IgG4-RD. Validation of the CDC demonstrated satisfactory sensitivity for the practical use of general physicians and nonspecialists but low sensitivity in the organs to be difficult in taking biopsy specimens such as type1 autoimmune pancreatitis (IgG4-related AIP), compared with IgG4-related sialadenitis/dacryoadenitis (Mikulicz's disease) and IgG4-related kidney disease. Although the diagnostic criteria covering all IgG4-RD are hard to be established, combination with the CDC and organ-specific diagnostic criteria should improve sensitivity.

Hashimoto thyroiditis: a century later

More than a century has passed since the first description of Hashimoto thyroiditis (HT) as a clinicopathologic entity. HT is an autoimmune disease in which a breakdown of immune tolerance is caused by interplay of a variety of immunologic, genetic, and environmental factors. Thyrocyte injury resulting from environmental factors results in expression of new or hidden epitopes that leads to proliferation of autoreactive T and B cells. Infiltration of thyroid by these cells results in HT. In addition to the usual type of HT, several variants such as the fibrous type and Riedal thyroiditis are also recognized. The most recently recognized variant is immunoglobulin G4(+) HT, which may occur as isolated thyroid limited disease or as part of a generalized Ig4-related sclerosing disease. The relationship between HT and Riedel thyroiditis remains unclear; however, recent evidence seems to suggest that it may also be part of the spectrum of Ig4-related sclerosing disease. HT is frequently associated with papillary thyroid carcinoma and may indeed be a risk factor for developing this type of cancer. The relationship between thyroid lymphoma and HT on the other hand appears well established.

Serum BAFF and APRIL levels in patients with IgG4-related disease and their clinical significance

INTRODUCTION

B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) play a crucial role in B cell development, survival, and antibody production. Here we analyzed the serum levels of BAFF and APRIL and their respective clinical associations in patients with an immunoglobulin (Ig) G4-related disease (IgG4-RD).

METHODS

We measured serum levels of BAFF and APRIL in patients with IgG4-RD, primary Sjögren's syndrome (pSS), and healthy individuals. Serum BAFF and APRIL levels in IgG4-RD were assessed for correlations with serological parameters, including Ig, particularly IgG4, and the number of affected organs. Serum BAFF and APRIL levels in IgG4-RD were monitored during glucocorticoid (GC) therapy.

RESULTS

Serum BAFF and APRIL levels in patients with IgG4-RD were significantly higher (P < 0.01) than in healthy individuals. The BAFF levels of patients with IgG4-RD were comparable to those of patients with pSS. Although clinical parameters, such as serum IgG4 and the number of affected organs, were not correlated with the levels of BAFF, serum APRIL levels were inversely correlated with serum IgG4 levels (r = -0.626, P < 0.05). While serum BAFF levels decreased following GC therapy, serum APRIL levels increased during follow-up.

CONCLUSION

These results indicate that BAFF and APRIL might be useful markers for predicting disease activity in IgG4-RD. Further studies are needed to elucidate the role of BAFF and APRIL in the pathogenesis of IgG4-RD.

The latest on IgG4-RD: a rapidly emerging disease

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

The Clinical and Pathological Features of IgG(4)-Related Disease

The rapidly emerging disorder now known as IgG(4)-related disease (IgG(4)-RD) includes a variety of clinical entities once regarded as being entirely separate diseases. Manifestations of IgG(4)-RD have now been reported in essentially all organ systems. Regardless of which organ is involved, tissue biopsies reveal striking histopathological similarities. The hallmark pathology findings are diffuse lymphoplasmacytic infiltrates, abundant IgG(4)-positive plasma cells, modest tissue eosinophilia, and extensive fibrosis. Tumorous swelling and obliterative phlebitis are other frequently observed features. Polyclonal elevations of serum IgG(4) are found in approximately 70% of patients. Many questions pertaining to the etiology, pathophysiology, epidemiology, clinical features, therapy, disease monitoring, and long-term outcomes remain to be addressed. This paper focuses on the clinical and pathological features of IgG(4)-RD.

High serum immunoglobulin G4-related retrosternal fibrosclerosis

A 65-year-old man with a history of exposure to asbestos complained of left leg edema. Computed tomography showed a flat, symmetrical, and longitudinal retrosternal thickening in addition to a presacral tumor. Retroperitoneal fibrosis was suspected. Serum immunoglobulin G4 (IgG4) levels were elevated (213 mg/dL). Thoracoscopic biopsy was performed. Histopathologic findings showed fibrotic tissue accompanied by proliferation of IgG4-positive plasma cells (proportion of IgG4/IgG-positive plasma cells ≥70%) indicative of multifocal fibrosclerosis.

Comprehensive diagnostic criteria for IgG4-related disease (IgG4-RD), 2011

BACKGROUND

IgG4-related disease (IgG4-RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4+ plasma cells. Although IgG4-RD is not rare and is clinically important, its clinical diagnostic criteria have not been established. Comprehensive diagnostic criteria for IgG4-RD, including the involvement of various organs, are intended for the practical use of general physicians and nonspecialists.

METHODS

Two IgG4-RD study groups, the Umehara and Okazaki teams, were organized by the Ministry of Health, Labor and Welfare Japan. As IgG4-RD comprises a wide variety of diseases, these groups consist of physicians and researchers in various disciplines, including rheumatology, hematology, gastroenterology, nephrology, pulmonology, ophthalmology, odontology, pathology, statistics, and basic and molecular immunology throughout Japan, with 66 and 56 members of the Umehara and Okazaki teams, respectively. Collaborations of the two study groups involved detailed analyses of clinical symptoms, laboratory results, and biopsy specimens of patients with IgG4-RD, resulting in the establishment of comprehensive diagnostic criteria for IgG4-RD.

RESULTS

Although many patients with IgG4-RD have lesions in several organs, either synchronously or metachronously, and the pathological features of each organ differ, consensus has been reached on two diagnostic criteria for IgG4RD: (1) serum IgG4 concentration >135 mg/dl, and (2) >40% of IgG+ plasma cells being IgG4+ and >10 cells/high powered field of biopsy sample. Although the comprehensive diagnostic criteria are not sufficiently sensitive for the diagnosis of type 1 IgG4-related autoimmune pancreatitis (IgG4-related AIP), they are adequately sensitive for IgG4-related Mikulicz's disease (MD) and kidney disease (KD). In addition, the comprehensive diagnostic criteria, combined with organ-specific diagnostic criteria, have increased the sensitivity of diagnosis to 100% for IgG4-related MD, KD, and AIP.

CONCLUSION

Our comprehensive diagnostic criteria for IgG4-RD are practically useful for general physicians and nonspecialists.

Rituximab for the treatment of IgG4-related disease: lessons from 10 consecutive patients

Patients with IgG4-related disease (IgG4-RD) typically have elevated serum concentrations of IgG4 and share histopathologic features that are similar across affected organ(s). IgG4-RD patients frequently require prolonged treatment with glucocorticoids and are often unable to taper these medications. Traditional disease-modifying antirheumatic drugs (DMARDs) are generally ineffective. We assessed the clinical and serologic responses to B lymphocyte depletion therapy in 10 consecutive patients with steroid- and DMARD-refractory IgG4-RD.Ten patients with IgG4-RD were treated with rituximab (RTX) (2 infusions of 1000 mg, 15 days apart). Clinical improvement was assessed by monitoring the patient's ability to taper prednisone to discontinuation and to stop DMARDs; by serial measurements of total IgG and IgG subclasses; and by follow-up radiologic assessments guided by the patient's particular pattern of organ involvement. We also developed and retrospectively applied the IgG4-RD Disease Activity Index and Flare Tool.Organ involvement included the pancreas, biliary tree, aorta, salivary glands (submandibular and parotid), lacrimal glands, lymph nodes, thyroid gland, and retroperitoneum. Nine of 10 patients demonstrated striking clinical improvement within 1 month of starting RTX. One patient with advanced thyroid fibrosis associated with Riedel thyroiditis and a history of disease in multiple other organ systems did not have improvement in the thyroid gland, but the disease did not progress to involve new organs. All 10 patients were able to discontinue prednisone and DMARDs following RTX therapy. Significant decreases in IgG concentrations were observed for the IgG4 subclass only. Four patients were re-treated with RTX after 6 months because of either symptom recurrence and increasing IgG4 concentration at the time of peripheral B cell reconstitution (n = 2) or because of physician discretion (n = 2). Repeated courses of RTX maintained their effectiveness and resulted in further decreases in IgG4 concentrations. In patients who had an increased IgG4 concentration at the time of presentation, the level of serum IgG4 appeared to be a reliable measure of disease activity.IgG4-RD is an idiopathic, multiorgan inflammatory disease in which diverse organ manifestations are linked by characteristic histopathologic and immunohistochemical features. Treatment with RTX led to prompt clinical and serologic improvement in refractory IgG4-RD in all patients with active inflammation. Serial treatments with RTX may lead to progressive declines in serum IgG4 concentrations and better disease control. Serum IgG4 concentrations may remain low, and clinical disease activity may remain quiescent even after B cell reconstitution in a significant proportion of patients.

IgG4-related sclerosing disease, an emerging entity: a review of a multi-system disease

Immunoglobulin G4-related systemic disease (IgG4-RSD) is a recently defined emerging entity characterized by a diffuse or mass forming inflammatory reaction rich in IgG4-positive plasma cells associated with fibrosclerosis and obliterative phlebitis. IgG4-RSD usually affects middle aged and elderly patients, with a male predominance. It is associated with an elevated serum titer of IgG4, which acts as a marker for this recently characterized entity. The prototype is IgG4-related sclerosing pancreatitis or autoimmune pancreatitis (AIP). Other common sites of involvement are the hepatobiliary tract, salivary gland, orbit, and lymph node, however practically any organ can be involved, including upper aerodigestive tract, lung, aorta, mediastinum, retroperitoneum, soft tissue, skin, central nervous system, breast, kidney, and prostate. Fever or constitutional symptoms usually do not comprise part of the clinical picture. Laboratory findings detected include raised serum globulin, IgG and IgG4. An association with autoantibody detection (such as antinuclear antibodies and rheumatoid factor) is seen in some cases. Steroid therapy comprises the mainstay of treatment. Disease progression with involvement of multiple organ-sites may be encountered in a subset of cases and may follow a relapsing-remitting course. The principal histopathologic findings in several extranodal sites include lymphoplasmacytic infiltration, lymphoid follicle formation, sclerosis and obliterative phlebitis, along with atrophy and destruction of tissues. Immunohistochemical staining shows increased IgG4+ cells in the involved tissues (>50 per high-power field, with IgG4/IgG ratio >40%). IgG4-RSD may potentially be rarely associated with the development of lymphoma and carcinoma. However, the nature and pathogenesis of IgG4-RSD are yet to be fully elucidated and provide immense scope for further studies.

Multifocal fibrosclerosis and IgG4-related disease involving the cardiovascular system

The cardiovascular system may be involved as a target organ of multifocal fibrosclerosis, which may manifest as idiopathic retroperitoneal fibrosis, inflammatory aortic aneurysm, inflammatory periarteritis, and inflammatory pericarditis. These pathological conditions can sometimes occur concomitantly. Idiopathic retroperitoneal fibrosis and inflammatory abdominal aortic aneurysm are both characterized by the presence of fibro-inflammatory tissue around the abdominal aorta expanding into the surrounding retroperitoneal structures, and together they may be termed 'chronic periaortitis'. Cardiovascular fibrosclerosis has become non-uncommonly encountered condition since imaging modalities have made its diagnosis more feasible. In addition, recent studies have demonstrated that a certain fraction, but not all, of cardiovascular fibrosclerosis may have a link with immunoglobulin-G4 (IgG4)-related sclerosing disease (IgG4-SD). IgG4-SD is histologically characterized by dense fibrosclerosis and infiltration of lymphocytes and IgG4-positive plasma cells, and these histopathologic findings seem to be essentially similar regardless of the organs involved. In this mini review, we summarize what is known so far about multifocal fibrosclerosis of the cardiovascular system and its association with IgG4-SD, and what remains to be clarified in future investigations.

[IgG4-related systemic disease: emergence of a new systemic disease? Literature review]

Hyper-IgG4 syndrome, or IgG4-related systemic disease (IgG4-RSD), has been recently characterized by the association of a focal or diffuse enlargement in one or more organs, elevated levels of serum IgG4 and histopathological findings including "storiform" fibrosis and prominent infiltration of lymphocytes and IgG4-positive plasma cells. Pancreas was the first organ involved with sclerosing pancreatitis (or autoimmune pancreatitis). Since this first description, many extrapancreatic lesions have been described, even in the absence of pancreatitis and include sialadenitis, lacrimal gland inflammation, lymphadenopathy, aortitis, sclerosing cholangitis, tubulointerstitial nephritis, retroperitoneal fibrosis or inflammatory pseudotumors. Multiorgan lesions can occur synchronously or metachronously in a same patient, usually after 50 years of age. They all share common histopathological findings. The disease often responds well to corticosteroid therapy. In this literature review on IgG4-RSD, we present historical, epidemiological and clinical characteristics, and we review the biological and histological diagnostic criteria. To date there is no international validated diagnostic criteria. Pathophysiological hypothesis and therapeutic approaches are also discussed.

Increased Numbers of IgG4-Positive Plasma Cells May Rarely Be Seen in Lymph Nodes of Patients Without IgG4-Related Sclerosing Disease

IgG4-related sclerosing disease (IRSD) is a steroid-responsive fibroinflammatory disorder characterized by increased IgG4+ cells. Nodal involvement usually lacks the dense sclerosis seen in extranodal sites, with histologic patterns overlapping with other reactive processes. Twenty-six lymph nodes showing IRSD-related histologic patterns were evaluated for IgG and IgG4 positive cells by immunohistochemistry and correlated with the clinical features. Cases included 7 Castleman disease–like cases (type I pattern), 10 follicular hyperplasia (type II), and 9 plasmacytosis (type III). The mean numbers of IgG4+ cells per high-power field (HPF) were 4.8 (I), 8.4 (II), and 26.6(III), and the mean IgG4/IgG ratios were 0.05 (I), 0.04 (II), and 0.08 (III). Using >50 IgG4+cells/HPF and IgG4/IgG ratio of >0.4 for absolute and relative increases, only 1 case fulfilled both criteria for increased IgG4+ cells, a patient with Hashimoto’s thyroiditis without clinical evidence of IRSD. The results suggest that increased IgG4+ cells may rarely be seen in non-IRSD lymph nodes.

Suspected idiopathic sclerosing orbital inflammation presenting as immunoglobulin G4-related disease: a case report

INTRODUCTION

Idiopathic sclerosing orbital inflammation is a rare and ill-defined heterogeneous entity, and a distinct subset of orbital inflammation. Recently, attention has been focused on immunoglobulin G4-related disease complicated with fibrotic changes in some other organs with high serum immunoglobulin G4 levels. This report presents a case of suspected idiopathic sclerosing orbital inflammation complicated with high serum immunoglobulin G4 levels.

CASE PRESENTATION

An 82-year-old Japanese woman had a 30-year history of chronic thyroiditis. She experienced right ptosis and eyelid swelling. These symptoms gradually developed over five years. The clinical and radiographic findings suggested that our patient had idiopathic sclerosing orbital inflammation. We were unable to obtain our patient's consent to perform a biopsy. While the serum immunoglobulin G level was within the normal limits, the serum immunoglobulin G4 level was significantly elevated. The serum immunoglobulin G4 levels decreased after the administration of oral prednisolone at a daily dose of 20 mg. In addition, the swelling and ptosis of the right upper eyelid disappeared gradually after four weeks. Our patient was then suspected to have idiopathic sclerosing orbital inflammation complicated with immunoglobulin G4-related disease and chronic thyroiditis.

CONCLUSION

An orbital pseudotumor of this type is indicative of idiopathic sclerosing orbital inflammation immunoglobulin G4-related disease. Immunoglobulin G4 may thus be considered a subclass of immunoglobulin G when the serum immunoglobulin G level is within normal limits.

A novel clinical entity, IgG4-related disease (IgG4RD): general concept and details

IgG4-related disease (IgG4RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. IgG4RD may be present in a certain proportion of patients with a wide variety of diseases, including Mikulicz’s disease, autoimmune pancreatitis, hypophysitis, Riedel thyroiditis, interstitial pneumonitis, interstitial nephritis, prostatitis, lymphadenopathy, retroperitoneal fibrosis, inflammatory aortic aneurysm, and inflammatory pseudotumor. Although IgG4RD forms a distinct, clinically independent disease category and is attracting strong attention as a new clinical entity, many questions and problems still remain to be elucidated, including its pathogenesis, the establishment of diagnostic criteria, and the role of IgG4. Here we describe the concept of IgG4RD and up-to-date information on this emerging disease entity.

Pathological features of IgG4-related sclerosing disease

PURPOSE OF REVIEW

The spectrum of IgG4-related systemic disease (IgG4-RSD) continues to widen. At most of the sites involved by this condition, the clinical presentation can mimic neoplasm. Pathologic assessment of small biopsies can be critical to proper management. This review summarizes the histologic features of IgG4-RSD and the role of immunohistochemistry of IgG4 in the diagnosis.

RECENT FINDINGS

The review period saw further expansion of the list of sites putatively involved by IgG4-RSD, with new, or more detailed, entries related to lung, lymph nodes, stomach, and thyroid. A tentative consensus was reached on the issue of subtypes of autoimmune pancreatitis. The role of immunohistochemistry for IgG4 as an adjunct to the diagnosis of IgG4-RSD was further clarified.

SUMMARY

Sclerosing lymphoplasmacytic inflammation at almost any site can represent a manifestation of IgG4-RSD. There are several histologic features that can suggest the diagnosis. Immunohistochemistry for IgG4 is a useful diagnostic test to further support the diagnosis.

What is IgG4? A review of the biology of a unique immunoglobulin subtype

PURPOSE OF REVIEW

Recent descriptions of the group of clinical disorders collectively defined as IgG4-related systemic disease (IgG4-RSD) have prompted this review of the unique biology of the IgG4 antibody. This article will discuss IgG4 structure and function, the unique phenomenon of half-antibody exchange, and the implications of IgG4 biology for its proposed role in immunologic diseases.

RECENT FINDINGS

IgG4 antibodies have unique structural and functional properties and undergo 'half-antibody exchange' in vivo, resulting in recombined antibodies composed of two different binding specificities. The production of IgG4 antibodies appears to be driven in part by T helper 2 (Th2) cytokines that mediate allergic responses and IgE production. Although serum IgG4 levels in healthy individuals vary significantly, data from multiple sclerosis (MS) patients suggest tight regulation of individual IgG4 levels over time. IgG4-RSD represents a diverse group of clinical disorders unified by elevated IgG4 levels and specific histopathologic findings. A key unanswered question is whether IgG4, a relatively weak activator of effector cells, is pathogenic in these disorders.

SUMMARY

IgG4 is a unique antibody biologically and structurally. Increased understanding of its precise role in the clinical syndromes that comprise IgG4-RSD may ultimately elucidate the underlying pathogenesis.

Treatment approaches to IgG4-related systemic disease

PURPOSE OF REVIEW

IgG4-related systemic disease (IgG4-RSD) is a systemic fibroinflammatory condition that can affect any organ system. Prompt recognition and management of this disease process are necessary to prevent sclerosis and permanent organ damage. Here, we review the advances in treatment approaches to IgG4-RSD.

RECENT FINDINGS

Most information regarding treatment is derived from retrospective case series of patients with autoimmune pancreatitis (AIP), and follow-up periods have generally been short. A variety of IgG4-RSD presentations respond rapidly to glucocorticoid treatment. Glucocorticoids have become a standard therapy for AIP, but the indications requiring treatment as well as the appropriate starting dose and duration of therapy remain controversial. The importance of maintenance of glucocorticoids following remission induction is debatable. As our knowledge grows regarding other organ manifestations of IgG4-RSD with longer follow-ups, the necessity of steroid-sparing agents to manage frequent relapses becomes clear.

SUMMARY

The natural history and long-term prognosis of IgG4-RSD are not well understood. Large prospective studies and randomized controlled trials of patients with wide spectrum manifestations of IgG4-RSD are required to support better approaches to treatment.

A clinical overview of IgG4-related systemic disease

PURPOSE OF REVIEW

To summarize the existing knowledge of various clinical presentations of IgG4-related systemic disease (IgG4-RSD) and to review the evolving list of organs affected by IgG4-RSD.

RECENT FINDINGS

The term IgG4-RSD encompasses a variety of clinical entities once regarded as being entirely separate diseases. The list of organs associated with this condition is growing steadily. Tissue biopsies reveal striking histopathological similarity, regardless of which organ is involved, although subtle differences across organs exist. Diffuse lymphoplasmacytic infiltrates, presence of abundant IgG4-positive plasma cells and extensive fibrosis are the hallmark pathology findings. Tumorous swelling, eosinophilia, and obliterative phlebitis are other frequently observed features. Polyclonal elevations of serum IgG4 are found in most but not all patients.

SUMMARY

IgG4-RSD is an underrecognized condition about which knowledge is now growing rapidly. Yet there remain many unknowns with regard to its cause, pathogenesis, various clinical presentations, approach to treatment, disease monitoring, and long-term outcomes. A wide variety of organs can be involved in IgG4-RSD. Clinicians should be aware of this entity and consider the diagnosis in the appropriate settings.