Thoracic IgG4-related Disease: Revealing the Diverse Imaging Manifestations.

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition characterized by IgG4-positive plasma cells, storiform fibrosis, obliterative phlebitis, and elevated serum IgG4 levels. Thoracic involvement commonly presents with mediastinal lymphadenopathy and peribronchovascular thickening, along with pulmonary abnormalities (nodules or masses, ground-glass opacities, fibrosis, consolidation, or cavities or cysts), pleural effusion or thickening, mediastinal or chest wall masses, and thoracic arteritis. Given the imaging overlap with other entities, a pattern-based approach is essential to narrow the differential diagnosis. Comprehensive radiologic evaluation across thoracic organs plays a pivotal role in early detection, timely treatment, and prevention of irreversible fibrosis.