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A 44‐year‐old man was referred to our hospital after an anterior mediastinal tumor was noted on computed tomography during follow‐up observation after left testicular seminoma resection. Chest computed tomography revealed an enhanced mass measuring 33 x 16 x 15 mm at the anterior mediastinum. Chest magnetic resonance imaging revealed high signal intensity on T2‐weighted imaging, and F18 fluorodeoxyglucose‐positron emission tomography showed a maximum standardized uptake of 12.45. Laboratory tests revealed no elevated tumor markers, except for mildly elevated interleukin‐2. Based on these results, complete resection was performed under suspicion of a malignant tumor, mediastinal metastasis of seminoma, or malignant lymphoma. An extended thymectomy with partial merger pericardial resection was performed using a subxiphoid approach. Small nodules and multiple thymic cysts were observed the thymus in addition to the main mass. Microscopic examination of the tumor revealed fibrosis, lymphocyte infiltration with lymphoid follicular hyperplasia, and hyperplasia of the thymus. Numerous immunoglobulin G4 (IgG4)‐positive plasma cells were found on immunohistochemical staining. The ratio of IgG4 to total IgG was approximately 60%. We ultimately diagnosed the patient with a thymic inflammatory pseudotumor with multilocular cyst caused by IgG4‐related disease.

IgG4‐related disease is characterized by a systemic fibroinflammatory process associated with substantial infiltration by plasma cells with IgG4 in the organs. Our patient presented with pleural effusion, and was diagnosed with IgG4‐related lung disease (IgG4‐RLD) after he received two doses of the Pfizer COVID‐19 vaccine. The patient developed dyspnea and hypoxia 2 weeks after receiving the second dose of the Pfizer COVID‐19 vaccine. CT scan revealed left pleural effusion which was drained. However, the effusion recurred requiring thoracoscopic drainage, placement of an indwelling catheter, and decortication with biopsy. IgG4 serum level was 268 mg/dl and pathology revealed pleural fibrosis, lymphoplasmacytic infiltrates, and increased IgG4‐positive plasma cells with no malignant cells leading to a diagnosis of IgG4‐RLD. Although COVID vaccine‐related IgG4‐RLD is a novel finding, having a high degree of suspicion following vaccination is always important for early diagnosis and effective treatment. We report the case of a patient who presented with pleural effusion, and was diagnosed with IgG4‐related lung disease (IgG4‐RLD) after he received two doses of the Pfizer COVID‐19 vaccine. Although COVID vaccine‐related IgG4‐RLD is a novel finding, having a high degree of suspicion following vaccination is always important for early diagnosis and effective treatment.

Background This study was undertaken in an attempt to characterize the frequency and clinical features of lung nodules in IgG4 related disease (IgG4-RD) patients as an insight for help with the diagnosis of lung nodules. Methods A retrospective study was carried out in West China Hospital, Sichuan University from January 2012 to December 2018, 89 patients with definite IgG4-RD were enrolled. Results Fifty of 89 patients with definite IgG4-RD had radiologically confirmed lung nodules, 6 of whom were diagnosed with definite IgG4 related lung disease. Lung nodules detected in more than 40 patients were small and solid, always with regular margins. Multiple (41/50) and bilateral (34/50) distributions was also a major characteristic of these lung nodules. Lobulation and speculation were simultaneously detected in 3 patients, including 2 patients combined with pleural indentation. Calcification of nodules was detected in only one patient. Thirty-seven patients also had additional radiological abnormalities of lungs, including ground-glass opacity (21/50), thickening of pleura (9/50), thickening of interlobular septa (4/50), thickening of bronchial wall (3/50), pleural effusion (4/50), mass (3/50), interstitial changes (5/50), and mediastinal or hilar lymphadenopathy (32/50). Most patients (44/50) were treated with glucocorticoids alone or combined with immunosuppressive agents. Sixteen patients received a re-examination by chest computed tomography (CT) scan after treatment, 10 of whom showed a decrease in the size and/or the number of nodules. Conclusions The incidence of lung nodules in IgG4-RD patients can be high. For an IgG4-RD patient with lung nodules, the possibility that the lung nodules related to IgG4-RLD is high. It is hard to differentiate IgG4 related lung nodules from other lung diseases, in particular, lung cancer. Radiological characteristics and positive responses to glucocorticoids and immunosuppressive agents can help with the differential diagnosis. For these patients, regular follow-up is also important.

Abstract We present the imaging findings in two cases of IgG4-related disease involving the sinonasal region in the pediatric age group. Imaging findings in IgG4-related disease affecting the nasal cavity and paranasal sinuses have been rarely reported in literature. The diagnosis is made by a combination of clinical, imaging, and histopathologic findings. Radiologists should be aware of the imaging findings of this condition to ensure early diagnosis and treatment.

Key message IgG4‐related lung disease (IgG4‐RLD) may present with a variety of radiological findings, but large lung mass lesion are rare. Although steroid therapy is strongly recommended for IgG4‐RLD with or without symptoms, respirologists should be aware that some patients may not need steroid therapy. IgG4‐related lung disease (IgG4‐RLD) may present with a variety of radiological findings, but large lung mass lesion are rare. Although steroid therapy is strongly recommended for IgG4‐RLD with or without symptoms, respirologists should be aware that some patients may not need steroid therapy.

ObjectivesIgG4-related disease (IgG4-RD) is an immune-mediated, fibroinflammatory disease. Induction treatment with glucocorticoid (GC) is usually effective, but its tendency of relapse makes the strategy for maintenance treatment a challenge. The WInS IgG4-RD (withdraw immunosuppressants (IMs) and steroid in stable IgG4-RD) trial tested whether discontinuation of GC and IM was feasible in stable IgG4-RD.MethodsThe WInS IgG4-RD trial was a multicentre, open-label, randomised controlled trial. Patients with IgG4-RD receiving GC+IM as maintenance treatment with clinically quiescent disease for at least 12 months were randomised (1:1:1) into three groups: group 1: withdraw GC+IM; group 2: withdraw GC but maintain IM; group 3: maintain GC+IM. The primary outcome was the relapse rate of disease within 18 months. The secondary outcomes included the changes of IgG4-RD Responder Index (RI), Physician’s Global Assessment (PGA), serum IgG4 and IgG, as well as adverse events.ResultsOne hundred and forty-six patients were randomised, with 48 patients in group 1, 49 patients in group 2 and group 3, respectively. Within the 18-month follow-up period, disease relapse occurred in 25 out of 48 (52.1%) patients in group 1 vs 7 out of 49 (14.2%) in group 2 and 6 out of 49 (12.2%) in group 3 (p<0.001). The changes in RI and PGA were significantly higher in group 1 than in group 2 (p<0.001) or group 3 (p<0.001).ConclusionsThe maintenance of IMs, with or without low-dose GC, was found to be superior to withdraw GC+IM in preventing relapse for long-time stable IgG4-RD.Trial registration number NCT04124861.

ObjectivesHypocomplementaemia is common in patients with IgG4-related disease (IgG4-RD). We aimed to determine the IgG4-RD features associated with hypocomplementaemia and investigate mechanisms of complement activation in this disease.MethodsWe performed a single-centre cross-sectional study of 279 patients who fulfilled the IgG4-RD classification criteria, using unadjusted and multivariable-adjusted logistic regression to identify factors associated with hypocomplementaemia.ResultsHypocomplementaemia was observed in 90 (32%) patients. In the unadjusted model, the number of organs involved (OR 1.42, 95% CI 1.23 to 1.63) and involvement of the lymph nodes (OR 3.87, 95% CI 2.19 to 6.86), lungs (OR 3.81, 95% CI 2.10 to 6.89), pancreas (OR 1.66, 95% CI 1.001 to 2.76), liver (OR 2.73, 95% CI 1.17 to 6.36) and kidneys (OR 2.48, 95% CI 1.47 to 4.18) were each associated with hypocomplementaemia. After adjusting for age, sex and number of organs involved, only lymph node (OR 2.59, 95% CI 1.36 to 4.91) and lung (OR 2.56, 95% CI 1.35 to 4.89) involvement remained associated with hypocomplementaemia while the association with renal involvement was attenuated (OR 1.6, 95% CI 0.92 to 2.98). Fibrotic disease manifestations (OR 0.43, 95% CI 0.21 to 0.87) and lacrimal gland involvement (OR 0.53, 95% CI 0.28 to 0.999) were inversely associated with hypocomplementaemia in the adjusted analysis. Hypocomplementaemia was associated with higher concentrations of all IgG subclasses and IgE (all p<0.05). After adjusting for serum IgG1 and IgG3, only IgG1 but not IgG4 remained strongly associated with hypocomplementaemia.ConclusionsHypocomplementaemia in IgG4-RD is not unique to patients with renal involvement and may reflect the extent of disease. IgG1 independently correlates with hypocomplementaemia in IgG4-RD, but IgG4 does not. Complement activation is likely involved in IgG4-RD pathophysiology.

A 67‐year‐old man with a history of asbestos exposure and rounded atelectasis complained of cough and swelling in the left submandibular region. Computed tomography showed an increase in size of the right lower lung lobe lesion, which was recognized as the pre‐existing rounded atelectasis, as well as swelling of the pancreas and submandibular glands. Biopsy from a submandibular gland and the pulmonary lesion led to a diagnosis of immunoglobulin G4‐related disease (IgG4‐RD). IgG4‐RD is a recently recognized disease that was first reported as an autoimmune disease; however, some reports have indicated another pathogenesis of an allergic nature that is characterized by type 2 helper T cell (Th2) inflammation. Additionally, it is recognized that long‐term exposure to asbestos can cause immune dysregulation. Here we present a case of IgG4‐RD associated with asbestos‐related pleural disease. Asbestos‐induced immune dysregulation may be one etiology of IgG4‐RD. IgG4‐RD is a recently recognized disease that was first reported as an autoimmune disease, however, some reports have indicated another pathogenesis. Here we present a case of IgG4‐RD associated with asbestos‐related pleural disease (ARPD). Asbestos‐induced immune dysregulation may be one etiology of IgG4‐RD.

Both immunoglobulin G4‐related disease (IgG4‐RD) and antineutrophil cytoplasmic antibody (ANCA)‐associated vasculitis (AAV) are systemic disorders that affect a wide range of organs. IgG4‐RD is characterized by tumor‐like swellings at multiple sites caused by IgG4‐positive plasma cells, obliterative phlebitis, and storiform fibrosis. AAV is a group of systemic autoimmune diseases characterized by primary inflammation of the small‐vessel walls. Although clinical studies have suggested similarities between AAV and IgG4‐RD, there are also significant differences. This review compares the similarities and differences between IgG4‐RD and AAV regarding etiology, organ involvement, clinical manifestations, laboratory features, pathology, and treatment. Smoking is a triggering factor for both IgG4‐RD and AAV. IgG4‐RD typically affects the pancreas, salivary glands, lacrimal glands, kidneys, and lymph nodes. AAV primarily targets the upper respiratory tract, lungs, and kidneys. IgG4‐RD often responds well to steroid therapy alone, whereas AAV typically requires the concomitant use of immunosuppressants. In addition, we discuss overlapping clinical cases to assist clinicians in recognizing these two diseases. Clinical perspectives and comparisons between immunoglobulin G4‐related disease and antineutrophil cytoplasmic antibody‐associated vasculitis. Key points IgG4‐RD typically affects the pancreas, salivary glands, lacrimal glands, kidneys, and lymph nodes. AAV primarily targets upper respiratory tract, lungs, and kidneys. Diagnosis of IgG4‐RD or AAV requires consideration of clinical manifestations, laboratory findings, and pathological evidence. We comprehensively analyze the clinical features, laboratory, and pathological characteristics of IgG4‐RD and AAV to elucidate their similarities and differences.