Abstract
We report the case of a 79-year-old male who presented with progressive dyspnea over the course of one month. Chest radiography revealed a left-sided pleural effusion. Pleural fluid analysis demonstrated an exudative profile with eosinophil-predominant cytology. Medical thoracoscopy identified multiple hyperpigmented spots on the anterior parietal pleura. Histopathological examination of pleural biopsy specimens confirmed the diagnosis of IgG4-related disease (IgG4-RD). The pleural effusion resolved completely following corticosteroid therapy.