IgG4 Related Disease Presenting With Eosinophilic Pleural Effusion

Area of Science:

• Pulmonology
• Rheumatology
• Immunology

Background:

• Eosinophilic pleural effusion (EPE) is an exudative effusion characterized by increased eosinophils.
• While common causes of EPE exist, rare etiologies require thorough investigation.
• Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory condition with diverse manifestations.

Purpose of the Study:

• To report an extremely rare case of IgG4-related pleural disease presenting as EPE.
• To emphasize the diagnostic challenges and importance of considering IgG4-RD in unexplained EPE.
• To contribute to the literature on IgG4-RD's pulmonary manifestations.

Main Methods:

• Clinical presentation of a 56-year-old man with chronic pleuritic chest pain and cough.
• Diagnostic workup including chest radiography, pleural fluid analysis (cytology, chemistry), and thoracoscopic pleural biopsy.
• Immunohistochemical staining for IgG4 and IgG, and serum IgG4 level measurement.

Main Results:

• Chest radiograph revealed right-sided pleural effusion.
• Pleural fluid analysis showed exudative effusion with abundant eosinophils and negative cytology.
• Histopathology and immunohistochemistry confirmed IgG4-related disease with elevated IgG4 staining and IgG4:IgG ratio.
• Serum IgG4 level was significantly elevated (300 mg/dL).

Conclusions:

• IgG4-related pleural disease is an exceedingly rare cause of eosinophilic pleural effusion.
• Diagnosis of IgG4-RD requires a combination of clinical, serological, and histopathological findings.
• This case underscores the need to consider IgG4-RD in the differential diagnosis of patients with unexplained EPE.