An initial exploration for comprehensive assessment of IgG4-related lung disease: analyses on the cases enrolled from a systematic review

Clinicopathological characteristics of IgG4-related lung disease

Background

Immunoglobulin G4-related lung disease (IgG4-RLD) is a rare entity. We retrospectively analyzed the clinical and histopathological characteristics of patients with pathologically confirmed IgG4-RLD to improve the diagnosis rate and reduce the risk of misdiagnosis.

Methods

We screened the pathological reports of 4838 patients with pulmonary surgery and/or biopsy specimens from April 2017 to April 2021 at Sun Yat-Sen Memorial Hospital affiliated with Sun Yat-Sen University, and specimens from 65 patients with suspected IgG4-RLD were subjected to immunohistochemical staining for IgG4 and IgG. Finally, 10 patients with definite IgG4-RLD that was pathologically confirmed were enrolled and analyzed.

Results

The incidence of pathologically confirmed IgG4-RLD was 0.2% (10/4838). The ten patients had an average age of 59.7 years at diagnosis, and the male-to-female ratio was 9:1. The initial clinical manifestations were nonspecific, and cough was the most common symptom (4/10). More than one organ was involved in most patients (8/10), and mediastinal/hilar lymph node involvement was often observed (7/10). Serum IgG4 was analyzed in 6 patients and found to be elevated. Serum tumor marker levels were within the normal range or were slightly elevated. Computed tomography (CT) of the chest and/or ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET-CT) imaging revealed that 5 patients had a mixed type, 3 patients had the solid nodular type, and 2 patients had the bronchovascular type. All pulmonary masses and large nodules with solid patterns had spiculated margins and inhomogeneous enhancement with or without pleural indentation and a lobulated appearance. Abundant lymphoplasmacytic cell infiltration and fibrosis were observed in all patients. The expression of IgG4 and IgG was upregulated in the pulmonary sections. Seven patients were treated with glucocorticoids with or without additional immunosuppressants and responded well.

Conclusions

The results of our study suggest that multiple imaging findings, an elevated serum IgG4 concentration, and no significant increase in serum tumor biomarkers could provide diagnostic support for IgG4-RLD, especially for isolated IgG4-RLD or IgG4-RLD that includes other organ involvement that does not aid in establishing the diagnosis.

An update on IgG4-related lung disease

IgG4-related disease (IgG4-RD) is an autoimmune disorder characterized by substantial infiltration of plasma cells with IgG4 in target organs. Lung manifestations predominantly present as inflammatory pseudotumor, interstitial pneumonitis, organizing pneumonia, and lymphomatoid granulomatosis. There is no specific diagnostic test for IgG4-related lung disease (IgG4-RLD), and excluding diseases that mimic IgG4-RLD is important. Corticosteroids with or without disease-modifying anti-rheumatic drugs are recommended for treatment. The long-term prognosis of IgG4-RLD remains unknown. In this review, we summarized the current diagnostic algorithms and discussed potential biomarkers for future investigation.

Thoracic Hyper-IgG4-Related Disease Mimicking Malignant Pleural Mesothelioma

We report a rare case of a IgG4-related disease presenting with recurrent pleural effusion, pleural thickness and multiple mediastinal lymphadenopathies and no involvement of other extrathoracic organs. A 65-year-old man with a previous asbestos exposure presented with cough and pain discomfort. A large right pleural effusion was detected and evacuated (siero-haematic liquid). With the suspicious of a pleural mesothelioma, a CT-scan before and a 18F-FDG PET/CT-scan later were performed revealing multiple pleural thickenings and multiple mediastinal lymphadenopathies with radiotracer uptake. EBUS-TBNA EBUS-TBNA did not result in a formal pathological diagnosis; thus, multiple pleural biopsy were performed via right thoracoscopy. At pathology the pleura was markedly thickened by a chronic fibroinflammatory process with scattered lymphoid follicles and a large number of mature plasma cells. Immunohistochemistry shows a mixed B (CD20+) and T (CD3+) population of lymphocytes, without light chain restriction and an increased number of IgG4-positive plasma cells. A presumptive diagnosis of IgG4-related disease was formulated. Total body CT-scan excluded other organ involvement. Blood test showed elevated serum IgG4 concentrations (253 mg/dL) and mild elevation of acute-phase reactants (C-reactive protein 10.7 mg/L). Autoimmune profile was negative. A diagnosis of definite IgG4-related disease was made, and treatment with prednisone 50 mg/day was started.