IgG4-related eosinophilic pleural effusion: a case report

BACKGROUND: The diagnosis of unilateral eosinophilic pleural effusion (EPE) is difficult, especially for the elderly. IgG4-related disease (IgG4-RD) is a rare cause of EPE. CASE PRESENTATION: An 81-year-old man was admitted to the hospital for dyspnea due to right pleural effusion. Laboratory examination shows elevated IgG4 and eosinophils in both serum and pleural fluid. The patient was diagnosed with IgG4-RD by video-assisted thoracoscopy and pleural biopsy. We found no evidence of other organ involvement except for the EPE and history of prurigo. He was treated with prednisolone 40 mg daily orally and pleural effusion decreased significantly. CONCLUSION: IgG4-RD should be considered in the differential diagnosis of EPE in the elderly. High effusion IgG4 concentration may be an indication of IgG4-related pleural lesions.