[IgG4-related disease-the diagnostic confusion and how to avoid it]

IgG4 autoantibodies and autoantigens in the context of IgG4-autoimmune disease and IgG4-related disease

Immunoglobulins are an essential part of the humoral immune response. IgG4 antibodies are the least prevalent subclass and have unique structural and functional properties. In this review, we discuss IgG4 class switch and B cell production. We review the importance of IgG4 antibodies in the context of allergic responses, helminth infections and malignancy. We discuss their anti-inflammatory and tolerogenic effects in allergen-specific immunotherapy, and ability to evade the immune system in parasitic infection and tumour cells. We then focus on the role of IgG4 autoantibodies and autoantigens in IgG4-autoimmune diseases and IgG4-related disease, highlighting important parallels and differences between them. In IgG4-autoimmune diseases, pathogenesis is based on a direct role of IgG4 antibodies binding to self-antigens and disturbing homeostasis. In IgG4-related disease, where affected organs are infiltrated with IgG4-expressing plasma cells, IgG4 antibodies may also directly target a number of self-antigens or be overexpressed as an epiphenomenon of the disease. These antigen-driven processes require critical T and B cell interaction. Lastly, we explore the current gaps in our knowledge and how these may be addressed.

Recommendations for evaluation and diagnosis of extra-glandular manifestations of primary Sjögren syndrome: results of an epidemiologic systematic review/meta-analysis and a consensus guideline from the Brazilian society of rheumatology (hepatic, gastrointestinal and pancreatic)

Sjogren's syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration of the exocrine glands and other organs, associated with sicca syndrome but also with systemic involvement with varying degrees of severity. Despite their importance, some systemic manifestations, mainly liver, gastrointestinal, and pancreatic are not routinely evaluated. To address these manifestations, the Sjögren's Syndrome Committee of the Brazilian Society of Rheumatology conducted a broad systematic review of the literature on studies investigating prevalence and diagnosis of these symptoms in Sjogren´s patients and made recommendations based on the findings. Agreement between the experts was achieved using the Delphi method. This is the second part of this guideline, providing 6 recommendations for liver, gastrointestinal, and pancreatic care of SS patients.

Granulomatosis with polyangiitis presenting as pancreatic disease

Granulomatosis with polyangiitis (GPA) is a rare necrotising small vessel vasculitis typically associated with oronasal, pulmonary and renal manifestations. Pancreatic disease is an exceedingly rare initial presentation and is associated with delayed diagnosis and rapid progression. We discuss a 66-year-old woman presenting with epigastric pain, elevated lipase and radiographic evidence of focal pancreatitis. She had no relevant medical history and no lithiasis seen on imaging. Pertinent findings include strawberry gingivitis, positive proteinase-antineutrophil cytoplasm antibody (98% specificity) and focal nodular parenchymal lung lesions on CT chest-all of which are consistent with a diagnosis of GPA. She was promptly started on high-dose steroids which resulted in significant clinical and biochemical improvement. Cyclophosphamide was added once biopsy confirmed the absence of malignancy. In order to optimise the clinical outcomes of GPA, physicians must keep a wide differential and high index of suspicion in the setting of unexplained pancreatitis with systemic features.

Clinical characteristics of Mikulicz's disease as an IgG4-related disease

OBJECTIVES

Mikulicz's disease (MD) was considered to be a subtype of Sjögren's syndrome (SS), based on histopathological similarities. However, recent studies have indicated that patients with MD show high serum IgG4 concentration, and suggested that MD is one of "IgG4-related disease" and distinguishable from SS. Therefore, we clinically and histopathologically examined the disease states of MD and SS in detail.

MATERIALS AND METHODS

Twenty patients with Mikulicz's disease and 18 with SS were comparatively studied to determine clinical characteristics in MD patients.

RESULTS

Sialography in MD patients did not show the "apple-tree sign" typically seen in SS. Serologically, high serum IgG4 levels but not anti-SS-A or anti-SS-B antibodies were observed in MD. SS showed lymphocytic infiltration of various subsets with atrophy or severe destruction of the acini, while MD showed selective infiltration of IgG4+ plasma cells with hyperplastic germinal centers and mild acini destruction. Corticosteroid treatment of MD reduced IgG and IgG4 levels and improved salivary function. A negative correlation between disease duration and increasing rate of salivary flow was observed in MD.

CONCLUSIONS

These results suggested that the pathogenesis of MD might be different from those of SS.

CLINICAL RELEVANCE

early diagnosis and treatment of MD is important for the improvement of salivary function.

Th2 and regulatory immune reactions contribute to IgG4 production and the initiation of Mikulicz disease

OBJECTIVE

Mikulicz disease has been considered to be a subtype of Sjögren's syndrome (SS). However, recent studies have suggested that Mikulicz disease is an IgG4-related disease and is distinguishable from SS. In addition, it has been reported that both interleukin-4 (IL-4) and IL-10 induce IgG4 production and inhibit IgE. This study was undertaken to examine the expression of these cytokines in patients with Mikulicz disease and patients with SS.

METHODS

Labial salivary gland (LSG) sections from 15 patients with Mikulicz disease and 18 patients with SS were examined for subsets of the infiltrating lymphocytes, expression patterns of messenger RNA (mRNA) for cytokines/chemokines, and relationships between the IgG4:IgG ratio and the expression of mRNA for IL-4 or IL-10.

RESULTS

Immunohistochemical analysis showed lymphocyte infiltration of various subsets in the LSGs of SS patients, and the selective infiltration of IgG4-positive plasma cells and Treg cells in the LSGs of Mikulicz disease patients. The levels of mRNA for both Th1 and Th2 cytokines and chemokines in LSGs from patients with SS were significantly higher than in controls, while the expression of both Th2 and Treg cells was significantly higher in the patients with Mikulicz disease than in controls. Furthermore, the expression of IL-4 or IL-10 in the LSGs was correlated with the IgG4:IgG ratio.

CONCLUSION

These results suggest that the pathogenesis of Mikulicz disease is different from that of SS. Mikulicz disease is a unique inflammatory disorder characterized by Th2 and regulatory immune reactions that might play key roles in IgG4 production.

IgG4-related disease: a novel lymphoproliferative disorder discovered and established in Japan in the 21st century

IgG4-related disease is a novel lymphoproliferative disorder that shows hyper-IgG4-γ-globulinemia and IgG4-producing plasma cell expansion in affected organs with fibrotic or sclerotic changes. Patients show systemic inflammatory conditions and various symptoms depending on the affected organ. Since the first report of patients with elevated serum IgG4 in sclerosing pancreatitis in 2001, various systemic disorders described by many names have been reported. Despite similarities in the organs involved in IgG4-related Mikulicz's disease and Sjögren's syndrome, there are marked clinical and pathological differences between these conditions. Most patients diagnosed with autoimmune pancreatitis in Japan have IgG4-related pancreatitis [Type 1 autoimmune pancreatitis (AIP), lymphoplasmacytic sclerosing pancreatitis (LPSP)], a disease distinct from some of the western type [Type 2 AIP, idiopathic duct-centric chronic pancreatitis (IDCP), autoimmune pancreatitis with granulocytic epithelial lesions (GEL)]. Diagnosis of IgG4-related disease is characterized by both elevated serum IgG4 (>135 mg/dL) and histopathological features including lymphocyte and IgG4(+) plasma cell infiltration (IgG4(+) plasma cells/IgG(+) plasma cells>40%). Differential diagnosis from other distinct disorders, such as sarcoidosis, Castleman's disease, Wegener's granulomatosis, lymphoma, cancer, and other existing conditions associated with high serum IgG4 level or abundant IgG4-bearing plasma cells in tissues is necessary. We have begun a clinical prospective study to establish a treatment strategy (Phase II prospective treatment study for IgG4-multiorgan lymphoproliferative syndrome: UMIN R000002311).

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.

Analysis of serum IgG subclasses in Churg-Strauss syndrome--the meaning of elevated serum levels of IgG4

OBJECTIVE

Mikulicz's disease (MD) is characterized by symmetrical and persistent enlargement of the lacrimal and salivary glands. Recently it has been categorized as an 'Ig (immunoglobulin) G4-related disease.' It presents with elevated serum levels of IgG4 and abundant infiltration of IgG4-bearing plasmacytes in involved organs. Allergic symptoms are often observed in patients with IgG4-related disease. On the other hand, allergic diseases are often complicated with Churg-Strauss syndrome (CSS). Here we focused on CSS and analyzed the relation of IgG4 in its pathogenesis.

MATERIALS AND METHODS

We analyzed five patients (2 men and 3 women) with CSS and 51 patients (20 men and 31 women) with MD who presented at Sapporo Medical University Hospital since 2001. We measured the serum concentrations of IgG subclasses in the patients with MD and CSS, and evaluated renal specimens from CSS patients, staining them for anti-IgG4 antibody.

RESULTS

We surprisingly found elevated serum levels of IgG4 not only in MD but also in CSS patients. The renal specimens in CSS patients revealed the infiltration of IgG4-positive plasmacytes.

CONCLUSION

IgG4-bearing plasmacytes may be involved in the pathogenesis of CSS, and it is possible that an allergic reaction plays an important role in the pathogenesis of IgG4-related disease.