A new clinical entity: IgG4-related disease (IgG4-RD) discovered in the 21st century

A Case of Tracheal Stenosis as an Isolated Form of Immunoproliferative Hyper-IgG4 Disease in a 17-Year-Old Girl

Immunoglobulin G4-related disease (IgG4-RD) is a lymphoproliferative disease which is described almost exclusively in adults. There are only a few pediatric patients who have been observed with this disorder. Here, we describe a rare case of IgG4-RD in a 17-year-old girl with a single manifestation—tracheal stenosis without previous intubation or other inciting event. She had mixed dyspnea and noisy and weakened breathing. Immunoproliferative hyper-IgG4 disease was diagnosed, based on elevated serum IgG4 and histological findings. Until now we have chosen to treat the girl only with corticosteroids with a good response so far. The general condition as well as the respiratory function are regularly monitored. The tracheal involvement of IgG4-RD is uncommon. Nonetheless, it is a manifestation that should be included in the differential diagnosis of tracheal stenosis.

The pronounced lung lesions developing in LATY136F knock-in mice mimic human IgG4-related lung disease

RATIONALE

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a novel clinical disease entity characterized by an elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. Pathological changes are most frequently seen in the pancreas, lacrimal glands, and salivary glands, but pathological changes in the lung also exist. Linker for activation of T cell (LAT)Y136F knock-in mice show Th2-dominant immunoreactions with elevated serum IgG1 levels, corresponding to human IgG4. We have reported that LATY136F knock-in mice display several characteristic features of IgG4-RD and concluded that they constitute an appropriate model of human IgG4-RD in salivary glands, pancreas, and kidney lesions.

OBJECTIVES

The aim of this study is to evaluate whether lung lesions in LATY136F knock-in mice can be a model of IgG4-related lung disease.

METHODS

Lung tissue samples from LATY136F knock-in mice (LAT) and wild-type mice (WT) were immunostained for IgG1 and obtained for pathological evaluation, and cell fractions and cytokine levels in broncho-alveolar lavage fluid (BALF) were analyzed.

RESULTS

In the LAT group, IgG1-positive inflammatory cells increased starting at 4 weeks of age and peaked at 10 weeks of age. The total cell count and percentage of lymphocytes increased significantly in BALF in the LAT group compared to the WT group. In BALF, Th2-dominant cytokines and transforming growth factor-β were also increased. In the LAT group, marked inflammation around broncho-vascular bundles peaked at 10 weeks of age. After 10 weeks, fibrosis around broncho-vascular bundles and bronchiectasis were observed in LATY136F knock-in mice but not WT mice.

CONCLUSIONS

LATY136F knock-in mice constitute an appropriate model of lung lesions in IgG4-RD.

LatY136F knock-in mouse model for human IgG4-related disease

Background

The adaptor protein Linker for activation of T cell (LAT) is a key signaling hub used by the T cell antigen receptor. Mutant mice expressing loss-of-function mutations affecting LAT and including a mutation in which tyrosine 136 is replaced by a phenylalanine (Lat^Y136F) develop lymphoproliferative disorder involving T helper type 2 effector cells capable of triggering a massive polyclonal B cell activation that leads to hypergammaglobulinemia G1 and E and to non-resolving inflammation and autoimmunity. The purpose of this study was to evaluate whether the phenotypes of Lat^Y136F knock-in mice resemble the immunohistopathological features of immunoglobulin G4-related disease (IgG4-RD).

Methods

Lat^Y136F knock-in mice were sacrificed at 4–20 weeks of age, and pancreas, kidney, salivary gland and lung were obtained. All organs were stained with hematoxylin-eosin and with Azan for estimation of collagen in fibrosis, and the severity scores of inflammation and fibrosis were evaluated. Immunostainings were performed to analyze the types of infiltrating cells. In addition, the effects of corticosteroid treatment on the development of tissue lesions and serum levels of IgG1 were assessed.

Results

Tissue lesions characterized by inflammatory mononuclear cell infiltration and fibrosis were detected in pancreas, kidney, and salivary gland starting from 6 weeks of age. Immunostainings showed pronounced infiltration of plasma cells, CD4-positive T cells, and macrophages. Infiltrating plasma cells predominantly expressed IgG1. The extent of inflammation in pancreas and salivary glands was markedly reduced by corticosteroid treatment.

Conclusions

Lat^Y136F knock-in mice displayed increased production of Th2-type IgG1 (a homologue of human IgG4) and developed multiple organ tissue lesions reminiscent of those seen in patients with IgG4-RD. Moreover, the development of these tissue lesions was highly sensitive to corticosteroid treatment like in IgG4-RD. For these reasons we consider the Lat^Y136F knock-in mouse strain to represent a promising model for human IgG4-RD.

Characteristics of immunoglobulin G4-related aortitis/periaortitis and periarteritis on fluorodeoxyglucose positron emission tomography/computed tomography co-registered with contrast-enhanced computed tomography

BACKGROUND

We aimed to assess the positivity, distribution, quantitative degree of vessel inflammation, and clinical characteristics of IgG4-related aortitis/periarteritis and periarteritis (IgG4-aortitis), and to examine the difference in these characteristics between cases with and without IgG4-aortitis, using fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) co-registered with contrast-enhanced CT (CECT). We retrospectively evaluated 37 patients with IgG4-related disease (IgG4-RD) who underwent both FDG-PET/CT and CECT. The arterial SUVmax and its value normalized to the background venous blood pool (BP)-the target-to-background ratio (TBR) in the entire aorta and the major first branches-were measured. Active vascular inflammation was considered in cases with a higher FDG uptake than BP and a thickened arterial wall (>2 mm).

RESULTS

Fifteen (41%) patients exhibited IgG4-aortitis. Most patients (80%) showed multiple region involvement. The entire aorta, including the major first branches, were involved, typically showing a thickened wall and high FDG uptakes. The most common site was the iliac arteries (35%), followed by the infrarenal abdominal aorta (33%), thoracic aorta (8%), first branches of the thoracic aorta (8%), suprarenal abdominal aorta (6%), and the first branches of the abdominal aorta (5%). The IgG4-aortitis-positive vessel regions were thickened, with an average maximal wall thickness of 6.3 ± 2.9 mm. The SUVmax and TBR values were significantly higher in the IgG4-aortitis-positive regions (median 3.7 [1.6-5.5] and 2.1 [1.4-3.7], respectively) than in the IgG4-aortitis-negative regions (median 2.1 [1.2-3.7] and 1.3 [0.9-2.3], respectively; p < 0.0001). The IgG4-aortitis-positive group patients were older (69.5 ± 6.0 vs. 63.3 ± 12.6 years, respectively) and had a higher male predominance (80 vs. 55%, respectively) than the negative group, although the differences were not significant (p = 0.17 and p = 0.06, respectively).

CONCLUSIONS

We investigated the image characteristics of IgG4-aortitis. The entire aorta and major branches can be involved with more than 2-fold higher FDG uptake than the venous background pool, and with wall thickening. The most common involved site is the iliac arteries, followed by the infrarenal abdominal aorta.

Roles of plasmablasts in IgG4-related disease and various immune-based diseases

IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory disease with multiple organ disorders. Recently, in IgG4-RD, increased circulating plasmablasts have been found. The subsets of plasmablasts are negative for RP105 (CD180). A large population of B cells lacking RP105 (RP105-negative B cells) are found in patients with active with systemic lupus erythematosus and other systemic autoimmune diseases, including dermatomyositis, and Sjögren’s syndrome. In other conditions, such as neuromyelitis optica, Kawasaki’s disease, primary biliary cirrhosis and aging, RP105 expression on B cells and monocytes also alters. We review the basic science and clinical significance of RP105-negative B cells including plasmablasts in various immune-based diseases. RP105-negative B cells, especially plasmablasts, play crucial roles in both systemic and organ-specific autoimmune and inflammatory disorders.

Overlap of IgG4-related Disease and Primary Biliary Cirrhosis Complicated with Autoimmune Thrombocytopenia

A 63-year-old woman was referred to Fukushima Red Cross Hospital with an enlargement of the left submandibular gland and subcutaneous bleeding in the chest and legs. A diffuse enlargement of the pancreas was also detected by abdominal computed tomography, and laboratory data showed severe thrombocytopenia. She was diagnosed with IgG4-related disease (IgG4-RD) complicated with autoimmune thrombocytopenia and was treated with methylprednisolone, after which the number of platelets favorably increased. Further investigation for liver dysfunction revealed underlying primary biliary cirrhosis (PBC). We herein report a rare case of IgG4-RD overlapping PBC complicated with autoimmune thrombocytopenia.

Immunoglobulin g4 non-related sclerosing disease with intracardiac mass mimicking mitral stenosis: case report

The cardiovascular system may be one of the target organs of both immunoglobulin G4 related and non-related systemic multifocal fibrosclerosis. We present a case of IgG4 non-related systemic multifocal fibrosclerosis mimicking mitral stenosis on echocardiography. For a more detailed differential diagnosis, we used multimodal imaging techniques. After surgical biopsy around the abdominal aortic area in the retroperitoneum, histological examination revealed IgG4 non-related systemic multifocal fibrosclerosis. We describe the multimodal imaging used to diagnose IgG4 non-related systemic multifocal fibrosclerosis and a positive response to steroid treatment. There have been no previous case reports of IgG4 non-related systemic multifocal fibrosclerosis with intracardiac involvement. Here, we report a case of IgG4 non-related systemic multifocal fibrosclerosis mimicking mitral stenosis.

Increased RP105-Negative B Cells in IgG4-Related Disease

Four patients with IgG4-related disease (IgG4-RD) showed increased percentages of RP105-negative B cells in the peripheral blood. Case 1: A 66-year-old man having retroperitoneal fibrosis had 18.8% of RP105-negative B cells. Oral prednisolone improved the affected lesions and the percentage of RP105-negative B cells decreased (3.2%) after the treatment. Case 2: A 53-year-old man with retroperitoneal fibrosis had 27.9% of RP105-negative B cells. Case 3: A 38-year-old man with follicular hyperplasia showed increased percentage of RP105-negative B cells (8.3%). Case 4: A 60-year-old man with interstitial nephritis had 27.5% of RP105-negative B cells. The treatment decreased the numbers of RP105-negative B cells. Increased numbers of RP105-negatvie B cells is possibly associated with disease activity of IgG4-RD. Analysis of expression of RP105 on B cells may be helpful in evaluation of disease activity of IgG4-RD.

Measurement of serum IgG4 levels by an established ELISA system and its clinical applications in autoimmune diseases

IgG4-related disease (IgG4-RD) is a novel and rare autoimmune disease entity. Elevated serum IgG4 level is strongly suggestive of IgG4-RD. But it is still unknown whether serum IgG4 elevation commonly occurs in other autoimmune diseases. In this study, the serum IgG4 levels were detected by an established enzyme-linked immunosorbent assay (ELISA) in a variety of autoimmune diseases including systemic lupus erythematosus (SLE), Sjogren's syndrome (SS), polymyositis or dermatomyositis (PM/DM) and IgG4-RD. To evaluate the reliability of this ELISA system, some of our samples were sent to a lab in Kanazawa Medical University, Japan, and detected by using the nephelometric assay. The results showed that our findings were consistent with theirs. Moreover, it was found that the serum IgG4 levels were 0.23±0.16 g/L in 53 healthy controls, 0.16±0.15 g/L in 103 SLE patients, 0.22±0.18 g/L in 41 SS patients and 0.40±0.32 g/L in 21 PM/DM patients. No significant difference in the serum IgG4 level was observed among these groups (P>0.05). The serum IgG4 levels of two cases of IgG4-RD were 1.63 and 4.65 g/L respectively, and both decreased markedly after treatment with glucocorticoids. These data indicated that this established ELISA system can be used for detecting serum IgG4 levels. Elevated serum IgG4 levels help diagnose IgG4-RD and evaluate the curative effect of this condition rather than other autoimmune diseases.

IgG4-related disease of the ureter: report of two cases and review of the literature

IgG4-related disease (IgG4-RD) is a recently recognized multi-organ fibro-inflammatory lesion characterized by elevated IgG4 serum levels and mass-forming lesions. This condition shows similar histological features independently of the site of origin including storiform fibrosis, obliterative phlebitis, and dense lymphoplasmacytic infiltrate with a conspicuous IgG4-positive plasma cell component. Since this disease has only recently been categorized as a single specific nosologic entity, lesions with these typical morphological features have previously been named in different ways, creating some confusion and making it difficult to identify cases published in the literature. Lesions with features suggesting IgG4-RDs have very rarely been reported in the ureter, and they have been named using the terms "inflammatory pseudotumor" and "idiopathic segmental ureteritis." Herein, we describe the clinicopathological features of ureteral IgG4-RD found in two different patients. An 82-year-old female and a 77-year-old male underwent ureteral resection due to severe ureteral wall thickness and lumen stenosis suggestive of urothelial carcinoma. However, histological examinations showed transmural fibro-inflammatory lesions, with abundant IgG4 plasma cells intermixed with histiocytes, lymphocytes, fibroblasts, and scattered eosinophils. We have also accurately reviewed the literature in order to identify, among lesions diagnosed with different names, examples of ureteral IgG4-related lesions to give the reader a comprehensive overview of this relatively rare inflammatory disease. We suggest using the name "ureteral IgG4-RD" for those lesions showing the same morphological features as IgG4-RDs located elsewhere.