Immunoglobulin G4-related Pleuritis Complicated with Minimal Change Disease

A 70-year-old woman with bilateral pleural effusion and respiratory failure was admitted to our hospital. Nephrotic syndrome due to minimal change disease had been diagnosed four months before admission. Because blood tests and a pleural fluid analysis did not reveal the etiology of her condition, we performed a video-assisted thoracoscopic pleural biopsy. No specific thoracoscopic findings were noted. The pathological findings revealed an increase in immunoglobulin G4 (IgG4)-positive cells; IgG4-related pleuritis was diagnosed. Her pleuritis improved with oral corticosteroid therapy. A further investigation was performed on previous kidney samples; however, the etiology of the nephrotic syndrome was not IgG4-related disease but minimal change disease.